1
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Weimann A, Dinan AM, Ruis C, Bernut A, Pont S, Brown K, Ryan J, Santos L, Ellison L, Ukor E, Pandurangan AP, Krokowski S, Blundell TL, Welch M, Blane B, Judge K, Bousfield R, Brown N, Bryant JM, Kukavica-Ibrulj I, Rampioni G, Leoni L, Harrison PT, Peacock SJ, Thomson NR, Gauthier J, Fothergill JL, Levesque RC, Parkhill J, Floto RA. Evolution and host-specific adaptation of Pseudomonas aeruginosa. Science 2024; 385:eadi0908. [PMID: 38963857 DOI: 10.1126/science.adi0908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 05/02/2024] [Indexed: 07/06/2024]
Abstract
The major human bacterial pathogen Pseudomonas aeruginosa causes multidrug-resistant infections in people with underlying immunodeficiencies or structural lung diseases such as cystic fibrosis (CF). We show that a few environmental isolates, driven by horizontal gene acquisition, have become dominant epidemic clones that have sequentially emerged and spread through global transmission networks over the past 200 years. These clones demonstrate varying intrinsic propensities for infecting CF or non-CF individuals (linked to specific transcriptional changes enabling survival within macrophages); have undergone multiple rounds of convergent, host-specific adaptation; and have eventually lost their ability to transmit between different patient groups. Our findings thus explain the pathogenic evolution of P. aeruginosa and highlight the importance of global surveillance and cross-infection prevention in averting the emergence of future epidemic clones.
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Affiliation(s)
- Aaron Weimann
- Victor Phillip Dahdaleh Heart & Lung Research Institute, University of Cambridge, Cambridge, UK
- University of Cambridge Molecular Immunity Unit, MRC Laboratory of Molecular Biology, Cambridge, UK
- Cambridge Centre for AI in Medicine, University of Cambridge, Cambridge, UK
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - Adam M Dinan
- Victor Phillip Dahdaleh Heart & Lung Research Institute, University of Cambridge, Cambridge, UK
- University of Cambridge Molecular Immunity Unit, MRC Laboratory of Molecular Biology, Cambridge, UK
- Cambridge Centre for AI in Medicine, University of Cambridge, Cambridge, UK
| | - Christopher Ruis
- Victor Phillip Dahdaleh Heart & Lung Research Institute, University of Cambridge, Cambridge, UK
- University of Cambridge Molecular Immunity Unit, MRC Laboratory of Molecular Biology, Cambridge, UK
- Cambridge Centre for AI in Medicine, University of Cambridge, Cambridge, UK
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - Audrey Bernut
- Laboratory of Pathogens and Host Immunity (LPHI), UMR5235, CNRS/Université de Montpellier, Montpellier, France
| | - Stéphane Pont
- Laboratory of Pathogens and Host Immunity (LPHI), UMR5235, CNRS/Université de Montpellier, Montpellier, France
| | - Karen Brown
- Victor Phillip Dahdaleh Heart & Lung Research Institute, University of Cambridge, Cambridge, UK
- University of Cambridge Molecular Immunity Unit, MRC Laboratory of Molecular Biology, Cambridge, UK
- Cambridge Centre for Lung Infection, Royal Papworth Hospital, Cambridge, UK
| | - Judy Ryan
- Victor Phillip Dahdaleh Heart & Lung Research Institute, University of Cambridge, Cambridge, UK
- University of Cambridge Molecular Immunity Unit, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Lúcia Santos
- Department of Physiology, Bioscience Institute, University College Cork, Cork, Ireland
| | - Louise Ellison
- University of Cambridge Molecular Immunity Unit, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Emem Ukor
- University of Cambridge Molecular Immunity Unit, MRC Laboratory of Molecular Biology, Cambridge, UK
- Cambridge Centre for Lung Infection, Royal Papworth Hospital, Cambridge, UK
| | - Arun P Pandurangan
- Victor Phillip Dahdaleh Heart & Lung Research Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
- Department of Medicine, University of Cambridge, Cambridge, UK
| | - Sina Krokowski
- Victor Phillip Dahdaleh Heart & Lung Research Institute, University of Cambridge, Cambridge, UK
- University of Cambridge Molecular Immunity Unit, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Tom L Blundell
- Victor Phillip Dahdaleh Heart & Lung Research Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
- Department of Medicine, University of Cambridge, Cambridge, UK
| | - Martin Welch
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Beth Blane
- Department of Medicine, University of Cambridge, Cambridge, UK
| | - Kim Judge
- Wellcome Sanger Institute, Hinxton, UK
| | - Rachel Bousfield
- Department of Medicine, University of Cambridge, Cambridge, UK
- Cambridge University Hospitals Trust, Cambridge, UK
| | | | | | - Irena Kukavica-Ibrulj
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec City, Québec, Canada
| | - Giordano Rampioni
- Department of Science, University Roma Tre, Rome, Italy
- IRCCS Fondazione Santa Lucia, Rome, Italy
| | - Livia Leoni
- Department of Science, University Roma Tre, Rome, Italy
| | - Patrick T Harrison
- Department of Physiology, Bioscience Institute, University College Cork, Cork, Ireland
| | - Sharon J Peacock
- Department of Medicine, University of Cambridge, Cambridge, UK
- Cambridge University Hospitals Trust, Cambridge, UK
| | - Nicholas R Thomson
- Wellcome Sanger Institute, Hinxton, UK
- London School of Hygiene and Tropical Medicine, London, UK
| | - Jeff Gauthier
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec City, Québec, Canada
| | - Jo L Fothergill
- Department of Clinical Infection, Microbiology and Immunology, University of Liverpool, Liverpool, UK
| | - Roger C Levesque
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec City, Québec, Canada
| | - Julian Parkhill
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - R Andres Floto
- Victor Phillip Dahdaleh Heart & Lung Research Institute, University of Cambridge, Cambridge, UK
- University of Cambridge Molecular Immunity Unit, MRC Laboratory of Molecular Biology, Cambridge, UK
- Cambridge Centre for AI in Medicine, University of Cambridge, Cambridge, UK
- Cambridge Centre for Lung Infection, Royal Papworth Hospital, Cambridge, UK
- Department of Medicine, University of Cambridge, Cambridge, UK
- Cambridge University Hospitals Trust, Cambridge, UK
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2
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Yin L, Liu Q, Pan X, Lv C, Bai Y, Bai F, Cheng Z, Wu W, Ha UH, Jin Y. MvaT binds to the P exsC promoter to repress the type III secretion system in Pseudomonas aeruginosa. Front Cell Infect Microbiol 2023; 13:1267748. [PMID: 38029243 PMCID: PMC10657842 DOI: 10.3389/fcimb.2023.1267748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 10/19/2023] [Indexed: 12/01/2023] Open
Abstract
Pseudomonas aeruginosa is an opportunistic human pathogen capable of causing a variety of acute and chronic infections. Its type III secretion system (T3SS) plays a critical role in pathogenesis during acute infection. ExsA is a master regulator that activates the expression of all T3SS genes. Transcription of exsA is driven by two distinct promoters, its own promoter PexsA and its operon promoter PexsC. Here, in combination with a DNA pull-down assay and mass spectrometric analysis, we found that a histone-like nucleoid-structuring (H-NS) family protein MvaT can bind to the PexsC promoter. Using EMSA and reporter assays, we further found that MvaT directly binds to the PexsC promoter to repress the expression of T3SS genes. The repression of MvaT on PexsC is independent of ExsA, with MvaT binding to the -429 to -380 bp region relative to the transcription start site of the exsC gene. The presented work further reveals the complex regulatory network of the T3SS in P. aeruginosa.
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Affiliation(s)
- Liwen Yin
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Qi Liu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Xiaolei Pan
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Chenjing Lv
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Yuxi Bai
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Fang Bai
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Zhihui Cheng
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Weihui Wu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Un-Hwan Ha
- Department of Biotechnology and Bioinformatics, Korea University, Sejong, Republic of Korea
| | - Yongxin Jin
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
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3
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Mekonnen SA, El Husseini N, Turdiev A, Carter JA, Belew AT, El-Sayed NM, Lee VT. Catheter-associated urinary tract infection by Pseudomonas aeruginosa progresses through acute and chronic phases of infection. Proc Natl Acad Sci U S A 2022; 119:e2209383119. [PMID: 36469780 PMCID: PMC9897465 DOI: 10.1073/pnas.2209383119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 11/08/2022] [Indexed: 12/12/2022] Open
Abstract
Healthcare-associated infections are major causes of complications that lead to extended hospital stays and significant medical costs. The use of medical devices, including catheters, increases the risk of bacterial colonization and infection through the presence of a foreign surface. Two outcomes are observed for catheterized patients: catheter-associated asymptomatic bacteriuria and catheter-associated urinary tract infection (CAUTI). However, the relationship between these two events remains unclear. To understand this relationship, we studied a murine model of Pseudomonas aeruginosa CAUTI. In this model, we also observe two outcomes in infected animals: acute symptoms that is associated with CAUTI and chronic colonization that is associated with asymptomatic bacteriuria. The timing of the acute outcome takes place in the first week of infection, whereas chronic colonization occurs in the second week of infection. We further showed that mutants lacking genes encoding type III secretion system (T3SS), T3SS effector proteins, T3SS injection pore, or T3SS transcriptional activation all fail to cause acute symptoms of CAUTI. Nonetheless, all mutants defective for T3SS colonized the catheter and bladders at levels similar to the parental strain. In contrast, through induction of the T3SS master regulator ExsA, all infected animals showed acute phenotypes with bacteremia. Our results demonstrated that the acute symptoms, which are analogous to CAUTI, and chronic colonization, which is analogous to asymptomatic bacteriuria, are independent events that require distinct bacterial virulence factors. Experimental delineation of asymptomatic bacteriuria and CAUTI informs different strategies for the treatment and intervention of device-associated infections.
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Affiliation(s)
- Solomon A. Mekonnen
- Department of Cell Biology and Molecular Genetics, University of Maryland at College Park, College Park, MD20742
| | - Nour El Husseini
- Department of Cell Biology and Molecular Genetics, University of Maryland at College Park, College Park, MD20742
| | - Asan Turdiev
- Department of Cell Biology and Molecular Genetics, University of Maryland at College Park, College Park, MD20742
| | - Jared A. Carter
- Department of Cell Biology and Molecular Genetics, University of Maryland at College Park, College Park, MD20742
| | - Ashton Trey Belew
- Department of Cell Biology and Molecular Genetics, University of Maryland at College Park, College Park, MD20742
| | - Najib M. El-Sayed
- Department of Cell Biology and Molecular Genetics, University of Maryland at College Park, College Park, MD20742
- Center for Bioinformatics and Computational Biology, University of Maryland at College Park, College Park, MD20742
| | - Vincent T. Lee
- Department of Cell Biology and Molecular Genetics, University of Maryland at College Park, College Park, MD20742
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4
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Lin Q, Huang J, Liu Z, Chen Q, Wang X, Yu G, Cheng P, Zhang LH, Xu Z. tRNA modification enzyme MiaB connects environmental cues to activation of Pseudomonas aeruginosa type III secretion system. PLoS Pathog 2022; 18:e1011027. [PMID: 36469533 PMCID: PMC9754610 DOI: 10.1371/journal.ppat.1011027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 12/15/2022] [Accepted: 11/28/2022] [Indexed: 12/12/2022] Open
Abstract
Pseudomonas aeruginosa, a major inhabitant of numerous environmental reservoirs, is a momentous opportunistic human pathogen associated with severe infections even death in the patients suffering from immune deficiencies or metabolic diseases. Type III secretion system (T3SS) employed by P. aeruginosa to inject effector proteins into host cells is one of the pivotal virulence factors pertaining to acute infections caused by this pathogen. Previous studies showed that P. aeruginosa T3SS is regulated by various environmental cues such as calcium concentration and the host signal spermidine. However, how T3SS is regulated and expressed particularly under the ever-changing environmental conditions remains largely elusive. In this study, we reported that a tRNA modification enzyme PA3980, designated as MiaB, positively regulated T3SS gene expression in P. aeruginosa and was essential for the induced cytotoxicity of human lung epithelial cells. Further genetic assays revealed that MiaB promoted T3SS gene expression by repressing the LadS-Gac/Rsm signaling pathway and through the T3SS master regulator ExsA. Interestingly, ladS, gacA, rsmY and rsmZ in the LadS-Gac/Rsm signaling pathway seemed potential targets under the independent regulation of MiaB. Moreover, expression of MiaB was found to be induced by the cAMP-dependent global regulator Vfr as well as the spermidine transporter-dependent signaling pathway and thereafter functioned to mediate their regulation on the T3SS gene expression. Together, these results revealed a novel regulatory mechanism for MiaB, with which it integrates different environmental cues to modulate T3SS gene expression in this important bacterial pathogen.
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Affiliation(s)
- Qiqi Lin
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
- School of Food Pharmaceutical Engineering, Zhao Qing University, Zhaoqing, China
| | - Jiahui Huang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
| | - Zhiqing Liu
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
| | - Qunyi Chen
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
| | - Xinbo Wang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
| | - Guohui Yu
- Institute of Plant Health, Zhongkai University of Agriculture and Engineering, Guangzhou, China
| | - Ping Cheng
- Institute of Plant Health, Zhongkai University of Agriculture and Engineering, Guangzhou, China
| | - Lian-Hui Zhang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
- * E-mail: (L-HZ); (ZX)
| | - Zeling Xu
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
- * E-mail: (L-HZ); (ZX)
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5
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Wang D, Zhang X, Yin L, Liu Q, Yu Z, Xu C, Ma Z, Xia Y, Shi J, Gong Y, Bai F, Cheng Z, Wu W, Lin J, Jin Y. RplI interacts with 5’ UTR of exsA to repress its translation and type III secretion system in Pseudomonas aeruginosa. PLoS Pathog 2022; 18:e1010170. [PMID: 34986198 PMCID: PMC8730436 DOI: 10.1371/journal.ppat.1010170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 12/04/2021] [Indexed: 11/19/2022] Open
Abstract
Pseudomonas aeruginosa is an important opportunistic pathogen capable of causing variety of infections in humans. The type III secretion system (T3SS) is a critical virulence determinant of P. aeruginosa in the host infections. Expression of the T3SS is regulated by ExsA, a master regulator that activates the expression of all known T3SS genes. Expression of the exsA gene is controlled at both transcriptional and posttranscriptional levels. Here, we screened a P. aeruginosa transposon (Tn5) insertional mutant library and found rplI, a gene coding for the ribosomal large subunit protein L9, to be a repressor for the T3SS gene expression. Combining real-time quantitative PCR (qPCR), western blotting and lacZ fusion assays, we show that RplI controls the expression of exsA at the posttranscriptional level. Further genetic experiments demonstrated that RplI mediated control of the exsA translation involves 5’ untranslated region (5’ UTR). A ribosome immunoprecipitation assay and qPCR revealed higher amounts of a 24 nt fragment from exsA mRNA being associated with ribosomes in the ΔrplI mutant. An interaction between RplI and exsA mRNA harboring its 24 nt, but not 12 nt, 5’ UTR was confirmed by RNA Gel Mobility Shift and Microscale Thermophoresis assays. Overall, this study identifies the ribosomal large subunit protein L9 as a novel T3SS repressor that inhibits ExsA translation in P. aeruginosa. Ribosomes provide all living organisms the capacity to synthesize proteins. The production of many ribosomal proteins is often controlled by an autoregulatory feedback mechanism. P. aeruginosa is an opportunistic human pathogen and its type III secretion system (T3SS) is a critical virulence determinant in host infections. In this study, by screening a Tn5 mutant library, we identified rplI, encoding ribosomal large subunit protein L9, as a novel repressor for the T3SS. Further exploring the regulatory mechanism, we found that the RplI protein interacts with the 5’ UTR (5’ untranslated region) of exsA, a gene coding for transcriptional activator of the T3SS. Such an interaction likely blocks ribosome loading on the exsA 5’ UTR, inhibiting the initiation of exsA translation. The significance of this work is in the identification of a novel repressor for the T3SS and elucidation of its molecular mechanism. Furthermore, this work provides evidence for individual ribosomal protein regulating mRNA translation beyond its autogenous feedback control.
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Affiliation(s)
- Dan Wang
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Xinxin Zhang
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Liwen Yin
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Qi Liu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Zhaoli Yu
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Congjuan Xu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Zhenzhen Ma
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Yushan Xia
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Jing Shi
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Yuehua Gong
- Cancer Institute, the First Affiliated Hospital of China Medical University, Shenyang, China
| | - Fang Bai
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Zhihui Cheng
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Weihui Wu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Jinzhong Lin
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Yongxin Jin
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
- * E-mail:
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6
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Silistre H, Raoux-Barbot D, Mancinelli F, Sangouard F, Dupin A, Belyy A, Deruelle V, Renault L, Ladant D, Touqui L, Mechold U. Prevalence of ExoY Activity in Pseudomonas aeruginosa Reference Panel Strains and Impact on Cytotoxicity in Epithelial Cells. Front Microbiol 2021; 12:666097. [PMID: 34675890 PMCID: PMC8524455 DOI: 10.3389/fmicb.2021.666097] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 07/30/2021] [Indexed: 11/13/2022] Open
Abstract
ExoY is among the effectors that are injected by the type III secretion system (T3SS) of Pseudomonas aeruginosa into host cells. Inside eukaryotic cells, ExoY interacts with F-actin, which stimulates its potent nucleotidyl cyclase activity to produce cyclic nucleotide monophosphates (cNMPs). ExoY has broad substrate specificity with GTP as a preferential substrate in vitro. How ExoY contributes to the virulence of P. aeruginosa remains largely unknown. Here, we examined the prevalence of active ExoY among strains from the international P. aeruginosa reference panel, a collection of strains that includes environmental and clinical isolates, commonly used laboratory strains, and sequential clonal isolates from cystic fibrosis (CF) patients and thus represents the large diversity of this bacterial species. The ability to secrete active ExoY was determined by measuring the F-actin stimulated guanylate cyclase (GC) activity in bacterial culture supernatants. We found an overall ExoY activity prevalence of about 60% among the 40 examined strains with no significant difference between CF and non-CF isolates. In parallel, we used cellular infection models of human lung epithelial cells to compare the cytotoxic effects of isogenic reference strains expressing active ExoY or lacking the exoY gene. We found that P. aeruginosa strains lacking ExoY were in fact more cytotoxic to the epithelial cells than those secreting active ExoY. This suggests that under certain conditions, ExoY might partly alleviate the cytotoxic effects of other virulence factors of P. aeruginosa.
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Affiliation(s)
- Hazel Silistre
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Dorothée Raoux-Barbot
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Federica Mancinelli
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Flora Sangouard
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Alice Dupin
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Alexander Belyy
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Vincent Deruelle
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Louis Renault
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Daniel Ladant
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Lhousseine Touqui
- Mucoviscidose: Physiopathologie et Phénogénomique, Centre de Recherche Saint-Antoine (CRSA), INSERM UMR S 938, Sorbonne Université, Paris, France.,Mucoviscidose et Bronchopathies Chroniques, Département Santé Globale, Institute Pasteur, Paris, France
| | - Undine Mechold
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
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7
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Cortés-Avalos D, Martínez-Pérez N, Ortiz-Moncada MA, Juárez-González A, Baños-Vargas AA, Estrada-de Los Santos P, Pérez-Rueda E, Ibarra JA. An update of the unceasingly growing and diverse AraC/XylS family of transcriptional activators. FEMS Microbiol Rev 2021; 45:6219864. [PMID: 33837749 DOI: 10.1093/femsre/fuab020] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 03/31/2021] [Indexed: 01/09/2023] Open
Abstract
Transcriptional factors play an important role in gene regulation in all organisms, especially in Bacteria. Here special emphasis is placed in the AraC/XylS family of transcriptional regulators. This is one of the most abundant as many predicted members have been identified and more members are added because more bacterial genomes are sequenced. Given the way more experimental evidence has mounded in the past decades, we decided to update the information about this captivating family of proteins. Using bioinformatics tools on all the data available for experimentally characterized members of this family, we found that many members that display a similar functional classification can be clustered together and in some cases they have a similar regulatory scheme. A proposal for grouping these proteins is also discussed. Additionally, an analysis of surveyed proteins in bacterial genomes is presented. Altogether, the current review presents a panoramic view into this family and we hope it helps to stimulate future research in the field.
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Affiliation(s)
- Daniel Cortés-Avalos
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, México
| | - Noemy Martínez-Pérez
- Instituto de Investigaciones en Matemáticas Aplicadas y en Sistemas, Universidad Nacional Autónoma de México, Unidad Académica Yucatán, Mérida, Yucatán, México
| | - Mario A Ortiz-Moncada
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, México
| | - Aylin Juárez-González
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, México
| | - Arturo A Baños-Vargas
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, México
| | - Paulina Estrada-de Los Santos
- Laboratorio de Biotecnología Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, México
| | - Ernesto Pérez-Rueda
- Instituto de Investigaciones en Matemáticas Aplicadas y en Sistemas, Universidad Nacional Autónoma de México, Unidad Académica Yucatán, Mérida, Yucatán, México.,Facultad de Ciencias, Centro de Genómica y Bioinformática, Universidad Mayor, Santiago, Chile
| | - J Antonio Ibarra
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, México
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8
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Fan K, Cao Q, Lan L. Genome-Wide Mapping Reveals Complex Regulatory Activities of BfmR in Pseudomonas aeruginosa. Microorganisms 2021; 9:485. [PMID: 33668961 PMCID: PMC8025907 DOI: 10.3390/microorganisms9030485] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 02/09/2021] [Accepted: 02/22/2021] [Indexed: 01/04/2023] Open
Abstract
BfmR is a response regulator that modulates diverse pathogenic phenotypes and induces an acute-to-chronic virulence switch in Pseudomonas aeruginosa, an important human pathogen causing serious nosocomial infections. However, the mechanisms of action of BfmR remain largely unknown. Here, using chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq), we showed that 174 chromosomal regions of P. aeruginosa MPAO1 genome were highly enriched by coimmunoprecipitation with a C-terminal Flag-tagged BfmR. Integration of these data with global transcriptome analyses revealed that 172 genes in 106 predicted transcription units are potential targets for BfmR. We determined that BfmR binds to and modulates the promoter activity of genes encoding transcriptional regulators CzcR, ExsA, and PhoB. Intriguingly, BfmR bound to the promoters of a number of genes belong to either CzcR or PhoB regulon, or both, indicating that CzcRS and PhoBR two-component systems (TCSs) deeply feed into the BfmR-mediated regulatory network. In addition, we demonstrated that phoB is required for BfmR to promote the biofilm formation by P. aeruginosa. These results delineate the direct BfmR regulon and exemplify the complexity of BfmR-mediated regulation of cellular functions in P. aeruginosa.
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Affiliation(s)
- Ke Fan
- University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing 100049, China;
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China;
| | - Qiao Cao
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China;
| | - Lefu Lan
- University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing 100049, China;
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China;
- School of Pharmaceutical Science and Technology, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310024, China
- NMPA Key Laboratory for Testing Technology of Pharmaceutical Microbiology, Shanghai Institute for Food and Drug Control, Shanghai 201203, China
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9
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Carruthers NJ, McClellan SA, Somayajulu M, Pitchaikannu A, Bessert D, Peng X, Huitsing K, Stemmer PM, Hazlett LD. Effects of Glycyrrhizin on Multi-Drug Resistant Pseudomonas aeruginosa. Pathogens 2020; 9:pathogens9090766. [PMID: 32962036 PMCID: PMC7557769 DOI: 10.3390/pathogens9090766] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 09/16/2020] [Indexed: 02/06/2023] Open
Abstract
The effects of glycyrrhizin (GLY) on multi-drug resistant (MDR) systemic (MDR9) vs. ocular (B1045) Pseudomonas aeruginosa clinical isolates were determined. Proteomes of each isolate with/without GLY treatment were profiled using liquid chromatography mass spectrometry (LC-MS/MS). The effect of GLY on adherence of MDR isolates to immortalized human (HCET) and mouse (MCEC) corneal epithelial cells, and biofilm and dispersal was tested. Both isolates were treated with GLY (0.25 minimum inhibitory concentration (MIC), 10 mg/mL for MDR9 and 3.75 mg/mL for B1045) and subjected to proteomic analysis. MDR9 had a greater response to GLY (51% of identified proteins affected vs. <1% in B1045). In MDR9 vs. controls, GLY decreased the abundance of proteins for: antibiotic resistance, biofilm formation, and type III secretion. Further, antibiotic resistance and type III secretion proteins had higher control abundances in MDR9 vs. B1045. GLY (5 and 10 mg/mL) significantly reduced binding of both isolates to MCEC, and B1045 to HCET. MDR9 binding to HCET was only reduced at 10 mg/mL GLY. GLY (5 and 10 mg/mL) enhanced dispersal for both isolates, at early (6.5 h) but not later times (24–72 h). This study provides evidence that GLY has a greater effect on the proteome of MDR9 vs. B1045, yet it was equally effective at disrupting adherence and early biofilm dispersal.
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Affiliation(s)
- Nicholas J. Carruthers
- Institute of Environmental Health Sciences, Wayne State University School of Medicine, 540 E. Canfield Avenue, Detroit, MI 48201, USA; (N.J.C.); (P.M.S.)
| | - Sharon A. McClellan
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University, School of Medicine, Detroit, MI 48201, USA; (S.A.M.); (M.S.); (A.P.); (D.B.); (K.H.)
| | - Mallika Somayajulu
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University, School of Medicine, Detroit, MI 48201, USA; (S.A.M.); (M.S.); (A.P.); (D.B.); (K.H.)
| | - Ahalya Pitchaikannu
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University, School of Medicine, Detroit, MI 48201, USA; (S.A.M.); (M.S.); (A.P.); (D.B.); (K.H.)
| | - Denise Bessert
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University, School of Medicine, Detroit, MI 48201, USA; (S.A.M.); (M.S.); (A.P.); (D.B.); (K.H.)
| | - Xudong Peng
- Department of Ophthalmology, The Affiliated Hospital of Qingdao University, Qingdao 266071, China;
| | - Kylie Huitsing
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University, School of Medicine, Detroit, MI 48201, USA; (S.A.M.); (M.S.); (A.P.); (D.B.); (K.H.)
| | - Paul M. Stemmer
- Institute of Environmental Health Sciences, Wayne State University School of Medicine, 540 E. Canfield Avenue, Detroit, MI 48201, USA; (N.J.C.); (P.M.S.)
| | - Linda D. Hazlett
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University, School of Medicine, Detroit, MI 48201, USA; (S.A.M.); (M.S.); (A.P.); (D.B.); (K.H.)
- Correspondence: ; Tel.: +1-313-577-1079; Fax: +1-313-577-3125
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10
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Janssen KH, Corley JM, Djapgne L, Cribbs JT, Voelker D, Slusher Z, Nordell R, Regulski EE, Kazmierczak BI, McMackin EW, Yahr TL. Hfq and sRNA 179 Inhibit Expression of the Pseudomonas aeruginosa cAMP-Vfr and Type III Secretion Regulons. mBio 2020; 11:e00363-20. [PMID: 32546612 PMCID: PMC7298702 DOI: 10.1128/mbio.00363-20] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 05/08/2020] [Indexed: 12/23/2022] Open
Abstract
Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen causing skin and soft tissue, respiratory, and bloodstream infections. The type III secretion system (T3SS) is one important virulence factor. Production of the T3SS is controlled by ExsA, a transcription factor that activates expression of the entire T3SS regulon. Global regulators including Vfr, RsmA, and Hfq also contribute to regulation of the T3SS. Vfr is a cAMP-responsive transcription factor that activates exsA transcription. RsmA, an RNA-binding protein, inversely controls expression of the T3SS and the type VI secretion system (T6SS). Hfq is an RNA chaperone that functions by stabilizing small noncoding RNAs (sRNAs) and/or facilitating base pairing between sRNAs and mRNA targets. A previous study identified sRNA 1061, which directly targets the exsA mRNA and likely inhibits ExsA synthesis. In this study, we screened an sRNA expression library and identified sRNA 179 as an Hfq-dependent inhibitor of T3SS gene expression. Further characterization revealed that sRNA 179 inhibits the synthesis of both ExsA and Vfr. The previous finding that RsmA stimulates ExsA and Vfr synthesis suggested that sRNA 179 impacts the Gac/Rsm system. Consistent with that idea, the inhibitory activity of sRNA 179 is suppressed in a mutant lacking rsmY and rsmZ, and sRNA 179 expression stimulates rsmY transcription. RsmY and RsmZ are small noncoding RNAs that sequester RsmA from target mRNAs. Our combined findings show that Hfq and sRNA 179 indirectly regulate ExsA and Vfr synthesis by reducing the available pool of RsmA, leading to reduced expression of the T3SS and cAMP-Vfr regulons.IMPORTANCE Control of gene expression by small noncoding RNA (sRNA) is well documented but underappreciated. Deep sequencing of mRNA preparations from Pseudomonas aeruginosa suggests that >500 sRNAs are generated. Few of those sRNAs have defined roles in gene expression. To address that knowledge gap, we constructed an sRNA expression library and identified sRNA 179 as a regulator of the type III secretion system (T3SS) and the cAMP-Vfr regulons. The T3SS- and cAMP-Vfr-controlled genes are critical virulence factors. Increased understanding of the signals and regulatory mechanisms that control these important factors will enhance our understanding of disease progression and reveal potential approaches for therapeutic intervention.
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Affiliation(s)
- Kayley H Janssen
- Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA
| | - Jodi M Corley
- Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA
| | - Louise Djapgne
- Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA
| | - J T Cribbs
- Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA
| | - Deven Voelker
- Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA
| | - Zachary Slusher
- Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA
| | - Robert Nordell
- Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA
| | - Elizabeth E Regulski
- Department of Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Barbara I Kazmierczak
- Department of Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA
| | | | - Timothy L Yahr
- Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA
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11
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Fleiszig SMJ, Kroken AR, Nieto V, Grosser MR, Wan SJ, Metruccio MME, Evans DJ. Contact lens-related corneal infection: Intrinsic resistance and its compromise. Prog Retin Eye Res 2019; 76:100804. [PMID: 31756497 DOI: 10.1016/j.preteyeres.2019.100804] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Revised: 11/05/2019] [Accepted: 11/12/2019] [Indexed: 12/20/2022]
Abstract
Contact lenses represent a widely utilized form of vision correction with more than 140 million wearers worldwide. Although generally well-tolerated, contact lenses can cause corneal infection (microbial keratitis), with an approximate annualized incidence ranging from ~2 to ~20 cases per 10,000 wearers, and sometimes resulting in permanent vision loss. Research suggests that the pathogenesis of contact lens-associated microbial keratitis is complex and multifactorial, likely requiring multiple conspiring factors that compromise the intrinsic resistance of a healthy cornea to infection. Here, we outline our perspective of the mechanisms by which contact lens wear sometimes renders the cornea susceptible to infection, focusing primarily on our own research efforts during the past three decades. This has included studies of host factors underlying the constitutive barrier function of the healthy cornea, its response to bacterial challenge when intrinsic resistance is not compromised, pathogen virulence mechanisms, and the effects of contact lens wear that alter the outcome of host-microbe interactions. For almost all of this work, we have utilized the bacterium Pseudomonas aeruginosa because it is the leading cause of lens-related microbial keratitis. While not yet common among corneal isolates, clinical isolates of P. aeruginosa have emerged that are resistant to virtually all currently available antibiotics, leading the United States CDC (Centers for Disease Control) to add P. aeruginosa to its list of most serious threats. Compounding this concern, the development of advanced contact lenses for biosensing and augmented reality, together with the escalating incidence of myopia, could portent an epidemic of vision-threatening corneal infections in the future. Thankfully, technological advances in genomics, proteomics, metabolomics and imaging combined with emerging models of contact lens-associated P. aeruginosa infection hold promise for solving the problem - and possibly life-threatening infections impacting other tissues.
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Affiliation(s)
- Suzanne M J Fleiszig
- School of Optometry, University of California, Berkeley, CA, USA; Graduate Group in Vision Science, University of California, Berkeley, CA, USA; Graduate Groups in Microbiology and Infectious Diseases & Immunity, University of California, Berkeley, CA, USA.
| | - Abby R Kroken
- School of Optometry, University of California, Berkeley, CA, USA
| | - Vincent Nieto
- School of Optometry, University of California, Berkeley, CA, USA
| | | | - Stephanie J Wan
- Graduate Group in Vision Science, University of California, Berkeley, CA, USA
| | | | - David J Evans
- School of Optometry, University of California, Berkeley, CA, USA; College of Pharmacy, Touro University California, Vallejo, CA, USA
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12
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H-NS Family Members MvaT and MvaU Regulate the Pseudomonas aeruginosa Type III Secretion System. J Bacteriol 2019; 201:JB.00054-19. [PMID: 30782629 DOI: 10.1128/jb.00054-19] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Accepted: 02/07/2019] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen capable of causing severe disease in immunocompromised individuals. A major P. aeruginosa virulence factor is the type III secretion system (T3SS). The T3SS is used to translocate effector proteins into host cells, causing cytotoxicity. The T3SS is under the transcriptional control of the master regulator ExsA. ExsA is encoded in the exsCEBA operon and autoregulates transcription via the P exsC promoter. There is also a Vfr-dependent promoter (P exsA ) located in the intergenic region between exsB and exsA A previous chromatin immunoprecipitation (ChIP)-on-chip experiment identified strong binding signatures for MvaT and MvaU in the intergenic region containing the P exsA promoter. MvaT and MvaU are DNA-binding histone-like nucleoid-structuring proteins that can repress gene expression. As predicted from the previous ChIP data, purified MvaT specifically bound to the P exsA promoter region in electrophoretic mobility shift assays. Whereas disruption of mvaT or mvaU by either transposon insertion or clustered regularly interspaced short palindromic repeat interference (CRISPRi) derepressed P exsA promoter activity and T3SS gene expression, overexpression of MvaT or MvaU inhibited P exsA promoter activity. Disruption of mvaT, however, did not suppress the Vfr requirement for P exsA promoter activity. Mutated MvaT/MvaU defective in transcriptional silencing exhibited dominant negative activity, resulting in a significant increase in P exsA promoter activity. Because no effect of MvaT or MvaU on Vfr expression was detected, we propose a model in which the primary effect of MvaT/MvaU on T3SS gene expression is through direct silencing of the P exsA promoter.IMPORTANCE Global regulatory systems play a prominent role in controlling the P. aeruginosa T3SS and include the Gac/RsmA, c-di-GMP, and Vfr-cAMP signaling pathways. Many of these pathways appear to directly or indirectly influence exsA transcription or translation. In this study, the histone-like proteins MvaT and MvaU are added to the growing list of global regulators that control the T3SS. MvaT and MvaU bind AT-rich regions in the genome and silence xenogeneic genes, including pathogenicity islands. The T3SS gene cluster has been horizontally transmitted among many Gram-negative pathogens. Control by MvaT/MvaU may reflect a residual effect that has persisted since the initial acquisition of the gene cluster, subsequently imposing a requirement for active regulatory mechanisms to override MvaT/MvaU-mediated silencing.
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13
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Fitting Pieces into the Puzzle of Pseudomonas aeruginosa Type III Secretion System Gene Expression. J Bacteriol 2019; 201:JB.00209-19. [PMID: 31010903 DOI: 10.1128/jb.00209-19] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Type III secretion systems (T3SS) are widely distributed in Gram-negative microorganisms and critical for host-pathogen and host-symbiont interactions with plants and animals. Central features of the T3SS are a highly conserved set of secretion and translocation genes and contact dependence wherein host-pathogen interactions trigger effector protein delivery and serve as an inducing signal for T3SS gene expression. In addition to these conserved features, there are pathogen-specific properties that include a unique repertoire of effector genes and mechanisms to control T3SS gene expression. The Pseudomonas aeruginosa T3SS serves as a model system to understand transcriptional and posttranscriptional mechanisms involved in the control of T3SS gene expression. The central regulatory feature is a partner-switching system that controls the DNA-binding activity of ExsA, the primary regulator of T3SS gene expression. Superimposed upon the partner-switching mechanism are cyclic AMP and cyclic di-GMP signaling systems, two-component systems, global regulators, and RNA-binding proteins that have positive and negative effects on ExsA transcription and/or synthesis. In the present review, we discuss advances in our understanding of how these regulatory systems orchestrate the activation of T3SS gene expression in the context of acute infections and repression of the T3SS as P. aeruginosa adapts to and colonizes the cystic fibrosis airways.
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14
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Zhang Y, Zhang C, Du X, Zhou Y, Kong W, Lau GW, Chen G, Kohli GS, Yang L, Wang T, Liang H. Glutathione Activates Type III Secretion System Through Vfr in Pseudomonas aeruginosa. Front Cell Infect Microbiol 2019; 9:164. [PMID: 31157178 PMCID: PMC6532553 DOI: 10.3389/fcimb.2019.00164] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 05/01/2019] [Indexed: 01/08/2023] Open
Abstract
Glutathione (GSH) is the most abundant antioxidant in all living organisms. Previously, we have shown that a deletion mutant in the glutathione synthetase gene (ΔgshB) decreases the expression of type III secretion system (T3SS) genes of Pseudomonas aeruginosa. However, the mechanism remains elusive. In this study, a comprehensive transcriptomic analysis of the GSH-deficient mutant ΔgshAΔgshB was used to elucidate the role of GSH in the pathogenesis of P. aeruginosa. The data show that the expression of genes in T3SS, type VI secretion system (T6SS) and some regulatory genes were impaired. ΔgshAΔgshB was attenuated in a mouse model of acute pneumonia, swimming and swarming motilities, and biofilm formation. Under T3SS inducing conditions, GSH enhanced the expression of T3SS in both wild-type PAO1 and ΔgshAΔgshB, but not in Δvfr. Genetic complementation of Δvfr restored the ability of GSH to induce the expression of T3SS genes. Site-directed mutagenesis based substitution of cysteine residues with alanine in Vfr protein abolished the induction of T3SS genes by GSH, confirming that GSH regulates T3SS genes through Vfr. Exposure to H2O2 decreased free thiol content on Vfr, indicating that the protein was sensitive to redox modification. Importantly, GSH restored the oxidized Vfr to reduced state. Collectively, these results suggest that GSH serves as an intracellular redox signal sensed by Vfr to upregulate T3SS expression in P. aeruginosa. Our work provides new insights into the role of GSH in P. aeruginosa pathogenesis.
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Affiliation(s)
- Yani Zhang
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi'an, China
| | - Chao Zhang
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi'an, China
| | - Xiao Du
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi'an, China
| | - Yun Zhou
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi'an, China
| | - Weina Kong
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi'an, China
| | - Gee W Lau
- Department of Pathobiology, University of Illinois at Urbana-Champaign, Champaign, IL, United States
| | - Gukui Chen
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi'an, China
| | - Gurjeet Singh Kohli
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore.,Alfred Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany
| | - Liang Yang
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore.,School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Tietao Wang
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi'an, China
| | - Haihua Liang
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi'an, China
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15
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Song Y, Yang C, Chen G, Zhang Y, Seng Z, Cai Z, Zhang C, Yang L, Gan J, Liang H. Molecular insights into the master regulator CysB-mediated bacterial virulence in Pseudomonas aeruginosa. Mol Microbiol 2019; 111:1195-1210. [PMID: 30618115 DOI: 10.1111/mmi.14200] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/04/2019] [Indexed: 12/21/2022]
Abstract
Pseudomonas aeruginosa is a major pathogen that causes serious acute and chronic infections in humans. The type III secretion system (T3SS) is an important virulence factor that plays essential roles in acute infections. However, the regulatory mechanisms of T3SS are not fully understood. In this study, we found that the deletion of cysB reduced the T3SS gene expression and swarming motility but enhanced biofilm formation. In a mouse acute pneumonia model, mutation of cysB decreased the average bacterial load compared to that of the wild-type strain. Further experiments demonstrated that CysB contributed to the reduced T3SS gene expression and bacterial pathogenesis by directly regulating the sensor kinase RetS. We also performed crystallographic studies of PaCysB. The overall fold of PaCysB NTD domain is similar to other LysR superfamily proteins and structural superposition revealed one possible DNA-binding model for PaCysB. Structural comparison also revealed great flexibility of the PaCysB RD domain, which may play an important role in bending and transcriptional regulation of target DNA. Taken together, these results expand our current understanding of the complex regulatory networks of T3SS and RetS pathways. The crystal structure of CysB provides new insights for studying the function of its homologs in other bacterial species.
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Affiliation(s)
- Yaqin Song
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, Shaanxi, 710069, China
| | - Chun Yang
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Gukui Chen
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, Shaanxi, 710069, China
| | - Yixi Zhang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, Shaanxi, 710069, China
| | - Zijing Seng
- School of Biological Sciences, Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Zhao Cai
- School of Biological Sciences, Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Chao Zhang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, Shaanxi, 710069, China
| | - Liang Yang
- School of Biological Sciences, Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, 639798, Singapore.,School of Medicine, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Jianhua Gan
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Haihua Liang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, Shaanxi, 710069, China
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16
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Deng X, Li M, Pan X, Zheng R, Liu C, Chen F, Liu X, Cheng Z, Jin S, Wu W. Fis Regulates Type III Secretion System by Influencing the Transcription of exsA in Pseudomonas aeruginosa Strain PA14. Front Microbiol 2017; 8:669. [PMID: 28469612 PMCID: PMC5395579 DOI: 10.3389/fmicb.2017.00669] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 03/31/2017] [Indexed: 11/21/2022] Open
Abstract
Fis is a versatile DNA binding protein in bacteria. It has been demonstrated in multiple bacteria that Fis plays crucial roles in regulating bacterial virulence factors and optimizing bacterial adaptation to various environments. However, the role of Fis in Pseudomonas aeruginosa virulence as well as gene regulation remains largely unknown. Here, we found that Fis was required for the virulence of P. aeruginosa in a murine acute pneumonia model. Transcriptome analysis revealed that expression of T3SS genes, including master regulator ExsA, was defective in a fis::Tn mutant. We further demonstrate that the continuous transcription of exsC, exsE, exsB, and exsA driven by the exsC promoter was required for the activation of T3SS. Fis was found to specifically bind to the exsB-exsA intergenic region and plays an essential role in the transcription elongation from exsB to exsA. Therefore, we found a novel role of Fis in the regulation of exsA expression.
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Affiliation(s)
- Xuan Deng
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai UniversityTianjin, China
| | - Mei Li
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai UniversityTianjin, China
| | - Xiaolei Pan
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai UniversityTianjin, China
| | - Ruiping Zheng
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai UniversityTianjin, China
| | - Chang Liu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai UniversityTianjin, China
| | - Fei Chen
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai UniversityTianjin, China
| | - Xue Liu
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai UniversityTianjin, China
| | - Zhihui Cheng
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai UniversityTianjin, China
| | - Shouguang Jin
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai UniversityTianjin, China.,Department of Molecular Genetics and Microbiology, College of Medicine, University of FloridaGainesville, FL, USA
| | - Weihui Wu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai UniversityTianjin, China
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17
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Zhao YH, Shaw JG. Cross-Talk between the Aeromonas hydrophila Type III Secretion System and Lateral Flagella System. Front Microbiol 2016; 7:1434. [PMID: 27656180 PMCID: PMC5013049 DOI: 10.3389/fmicb.2016.01434] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 08/29/2016] [Indexed: 01/09/2023] Open
Abstract
Aeromonas hydrophila is responsible for aeromonad septicaemia in fish, and gastroenteritis and wound infections in humans. The type III secretion system (T3SS) is utilized by aeromonads to inject protein effectors directly into host cells. One of the major genetic regulators of the T3SS in several bacterial species is the AraC-like protein ExsA. Previous studies have suggested a link between T3SS regulation and lateral flagella expression. The aim of this study was to determine the genetic regulation of the T3SS and its potential interaction with the lateral flagella system in A. hydrophila. To investigate the genes encoding the T3SS regulatory components exsA, exsD, exsC, and exsE were mutated and the activities of the T3SS promoters were measured in wild type and mutant backgrounds demonstrating a regulatory network. The Exs proteins were shown to interact with each other by BACTH assay and Far-Western Blot. The findings suggested a regulatory cascade in which ExsE was bound to the chaperone protein ExsC. When ExsC was free it sequestered the anti-activator ExsD thus stopping the inhibition of the T3SS master regulator ExsA allowing T3SS expression. The T3SS regulatory components were also shown to affect the expression of the lateral flagella system. The activities of the lateral flagella promoters were shown to be repressed by the absence of ExsD and ExsE, suggesting that the T3SS master regulator ExsA was a negative regulator of the lateral flagella system.
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Affiliation(s)
- Yu-Hang Zhao
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield Sheffield, UK
| | - Jonathan G Shaw
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield Sheffield, UK
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Vfr Directly Activates exsA Transcription To Regulate Expression of the Pseudomonas aeruginosa Type III Secretion System. J Bacteriol 2016; 198:1442-50. [PMID: 26929300 DOI: 10.1128/jb.00049-16] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 02/21/2016] [Indexed: 02/04/2023] Open
Abstract
UNLABELLED The Pseudomonas aeruginosa cyclic AMP (cAMP)-Vfr system (CVS) is a global regulator of virulence gene expression. Regulatory targets include type IV pili, secreted proteases, and the type III secretion system (T3SS). The mechanism by which CVS regulates T3SS gene expression remains undefined. Single-cell expression studies previously found that only a portion of the cells within a population express the T3SS under inducing conditions, a property known as bistability. We now report that bistability is altered in avfr mutant, wherein a substantially smaller fraction of the cells express the T3SS relative to the parental strain. Since bistability usually involves positive-feedback loops, we tested the hypothesis that virulence factor regulator (Vfr) regulates the expression of exsA ExsA is the central regulator of T3SS gene expression and autoregulates its own expression. Although exsA is the last gene of the exsCEBA polycistronic mRNA, we demonstrate that Vfr directly activates exsA transcription from a second promoter (PexsA) located immediately upstream of exsA PexsA promoter activity is entirely Vfr dependent. Direct binding of Vfr to a PexsA promoter probe was demonstrated by electrophoretic mobility shift assays, and DNase I footprinting revealed an area of protection that coincides with a putative Vfr consensus-binding site. Mutagenesis of that site disrupted Vfr binding and PexsA promoter activity. We conclude that Vfr contributes to T3SS gene expression through activation of the PexsA promoter, which is internal to the previously characterized exsCEBA operon. IMPORTANCE Vfr is a cAMP-dependent DNA-binding protein that functions as a global regulator of virulence gene expression in Pseudomonas aeruginosa Regulation by Vfr allows for the coordinate production of related virulence functions, such as type IV pili and type III secretion, required for adherence to and intoxication of host cells, respectively. Although the molecular mechanism of Vfr regulation has been defined for many target genes, a direct link between Vfr and T3SS gene expression had not been established. In the present study, we report that Vfr directly controls exsA transcription, the master regulator of T3SS gene expression, from a newly identified promoter located immediately upstream of exsA.
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19
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Zhu M, Zhao J, Kang H, Kong W, Liang H. Modulation of Type III Secretion System in Pseudomonas aeruginosa: Involvement of the PA4857 Gene Product. Front Microbiol 2016; 7:7. [PMID: 26858696 PMCID: PMC4729953 DOI: 10.3389/fmicb.2016.00007] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 01/06/2016] [Indexed: 11/21/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that causes serious acute or chronic infections in humans. Acute infections typically involve the type III secretion systems (T3SSs) and bacterial motility, whereas chronic infections are often associated with biofilm formation and the type VI secretion system. To identify new genes required for pathogenesis, a transposon mutagenesis library was constructed and the gene PA4857, named tspR, was found to modulate T3SS gene expression. Deletion of P. aeruginosa tspR reduced the virulence in a mouse acute lung infection model and diminished cytotoxicity. Suppression of T3SS gene expression in the tspR mutant resulted from compromised translation of the T3SS master regulator ExsA. TspR negatively regulated two small RNAs, RsmY and RsmZ, which control RsmA. Our data demonstrated that defects in T3SS expression and biofilm formation in retS mutant could be partially restored by overexpression of tspR. Taken together, our results demonstrated that the newly identified retS-tspR pathway is coordinated with the retS-gacS system, which regulates the genes associated with acute and chronic infections and controls the lifestyle choice of P. aeruginosa.
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Affiliation(s)
- Miao Zhu
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, Department of Life Science, Northwest University Xi'an, China
| | - Jingru Zhao
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, Department of Life Science, Northwest University Xi'an, China
| | - Huaping Kang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, Department of Life Science, Northwest University Xi'an, China
| | - Weina Kong
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, Department of Life Science, Northwest University Xi'an, China
| | - Haihua Liang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, Department of Life Science, Northwest University Xi'an, China
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20
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Abstract
Many Gram-negative pathogens express a type III secretion (T3SS) system to enable growth and survival within a host. The three human-pathogenic Yersinia species, Y. pestis, Y. pseudotuberculosis, and Y. enterocolitica, encode the Ysc T3SS, whose expression is controlled by an AraC-like master regulator called LcrF. In this review, we discuss LcrF structure and function as well as the environmental cues and pathways known to regulate LcrF expression. Similarities and differences in binding motifs and modes of action between LcrF and the Pseudomonas aeruginosa homolog ExsA are summarized. In addition, we present a new bioinformatics analysis that identifies putative LcrF binding sites within Yersinia target gene promoters.
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21
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The importance of the Pseudomonas aeruginosa type III secretion system in epithelium traversal depends upon conditions of host susceptibility. Infect Immun 2015; 83:1629-40. [PMID: 25667266 DOI: 10.1128/iai.02329-14] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Pseudomonas aeruginosa is invasive or cytotoxic to host cells, depending on the type III secretion system (T3SS) effectors encoded. While the T3SS is known to be involved in disease in vivo, how it participates remains to be clarified. Here, mouse models of superficial epithelial injury (tissue paper blotting with EGTA treatment) and immunocompromise (MyD88 deficiency) were used to study the contribution of the T3SS transcriptional activator ExsA to epithelial traversal. Corneas of excised eyeballs were inoculated with green fluorescent protein (GFP)-expressing PAO1 or isogenic exsA mutants for 6 h ex vivo before bacterial traversal and epithelial thickness were quantified by using imaging. In the blotting-EGTA model, exsA mutants were defective in capacity for traversal. Accordingly, an ∼16-fold variability in exsA expression among PAO1 isolates from three sources correlated with epithelial loss. In contrast, MyD88-/- epithelia remained susceptible to P. aeruginosa traversal despite exsA mutation. Epithelial lysates from MyD88-/- mice had reduced antimicrobial activity compared to those from wild-type mice with and without prior antigen challenge, particularly 30- to 100-kDa fractions, for which mass spectrometry revealed multiple differences, including (i) lower baseline levels of histones, tubulin, and lumican and (ii) reduced glutathione S-transferase, annexin, and dermatopontin, after antigen challenge. Thus, the importance of ExsA in epithelial traversal by invasive P. aeruginosa depends on the compromise enabling susceptibility, suggesting that strategies for preventing infection will need to extend beyond targeting the T3SS. The data also highlight the importance of mimicking conditions allowing susceptibility in animal models and the need to monitor variability among bacterial isolates from different sources, even for the same strain.
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Liang H, Deng X, Li X, Ye Y, Wu M. Molecular mechanisms of master regulator VqsM mediating quorum-sensing and antibiotic resistance in Pseudomonas aeruginosa. Nucleic Acids Res 2014; 42:10307-20. [PMID: 25034696 PMCID: PMC4176358 DOI: 10.1093/nar/gku586] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The Pseudomonas aeruginosa quorum-sensing (QS) systems contribute to bacterial homeostasis and pathogenicity. Although the AraC-family transcription factor VqsM has been characterized to control the production of virulence factors and QS signaling molecules, its detailed regulatory mechanisms still remain elusive. Here, we report that VqsM directly binds to the lasI promoter region, and thus regulates its expression. To identify additional targets of VqsM in P. aeruginosa PAO1, we performed chromatin immunoprecipitation (ChIP) followed by high-throughput DNA sequencing (ChIP-seq) and detected 48 enriched loci harboring VqsM-binding peaks in the P. aeruginosa genome. The direct regulation of these genes by VqsM has been confirmed by electrophoretic mobility shift assays and quantitative real-time polymerase chain reactions. A VqsM-binding motif was identified by using the MEME suite and verified by footprint assays in vitro. In addition, VqsM directly bound to the promoter regions of the antibiotic resistance regulator NfxB and the master type III secretion system (T3SS) regulator ExsA. Notably, the vqsM mutant displayed more resistance to two types of antibiotics and promoted bacterial survival in a mouse model, compared to wild-type PAO1. Collectively, this work provides new cues to better understand the detailed regulatory networks of QS systems, T3SS, and antibiotic resistance.
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Affiliation(s)
- Haihua Liang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Science, Northwest University, Xi'an, ShaanXi 710069, China Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Xin Deng
- Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Xuefeng Li
- Department of Basic Science, School of Medicine and Health Science, University of North Dakota, 501 North Columbia Rd, EJRF Building, Room 2726, ND 58203, USA
| | - Yan Ye
- Department of Basic Science, School of Medicine and Health Science, University of North Dakota, 501 North Columbia Rd, EJRF Building, Room 2726, ND 58203, USA
| | - Min Wu
- Department of Basic Science, School of Medicine and Health Science, University of North Dakota, 501 North Columbia Rd, EJRF Building, Room 2726, ND 58203, USA
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23
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Lucchetti-Miganeh C, Redelberger D, Chambonnier G, Rechenmann F, Elsen S, Bordi C, Jeannot K, Attrée I, Plésiat P, de Bentzmann S. Pseudomonas aeruginosa Genome Evolution in Patients and under the Hospital Environment. Pathogens 2014; 3:309-40. [PMID: 25437802 PMCID: PMC4243448 DOI: 10.3390/pathogens3020309] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Revised: 03/26/2014] [Accepted: 03/28/2014] [Indexed: 11/21/2022] Open
Abstract
Pseudomonas aeruginosa is a Gram-negative environmental species and an opportunistic microorganism, establishing itself in vulnerable patients, such as those with cystic fibrosis (CF) or those hospitalized in intensive care units (ICU). It has become a major cause of nosocomial infections worldwide and a serious threat to Public Health because of overuse and misuse of antibiotics that have selected highly resistant strains against which very few therapeutic options exist. Herein is illustrated the intraclonal evolution of the genome of sequential isolates collected in a single CF patient from the early phase of pulmonary colonization to the fatal outcome. We also examined at the whole genome scale a pair of genotypically-related strains made of a drug susceptible, environmental isolate recovered from an ICU sink and of its multidrug resistant counterpart found to infect an ICU patient. Multiple genetic changes accumulated in the CF isolates over the disease time course including SNPs, deletion events and reduction of whole genome size. The strain isolated from the ICU patient displayed an increase in the genome size of 4.8% with major genetic rearrangements as compared to the initial environmental strain. The annotated genomes are given in free access in an interactive web application WallGene designed to facilitate large-scale comparative analysis and thus allowing investigators to explore homologies and syntenies between P. aeruginosa strains, here PAO1 and the five clinical strains described.
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Affiliation(s)
| | - David Redelberger
- UMR7255-Laboratoire d'Ingénierie des Systèmes Macromoléculaires, CNRS-Aix Marseille University, Marseille 13402, France.
| | - Gaël Chambonnier
- UMR7255-Laboratoire d'Ingénierie des Systèmes Macromoléculaires, CNRS-Aix Marseille University, Marseille 13402, France.
| | | | - Sylvie Elsen
- INSERM, UMR-S 1036, Biology of Cancer and Infection, Grenoble 38054, France.
| | - Christophe Bordi
- UMR7255-Laboratoire d'Ingénierie des Systèmes Macromoléculaires, CNRS-Aix Marseille University, Marseille 13402, France.
| | - Katy Jeannot
- Laboratoire de Bactériologie, Faculté de Médecine-Pharmacie, Université de Franche-Comté, Besançon 25030, France.
| | - Ina Attrée
- INSERM, UMR-S 1036, Biology of Cancer and Infection, Grenoble 38054, France.
| | - Patrick Plésiat
- Laboratoire de Bactériologie, Faculté de Médecine-Pharmacie, Université de Franche-Comté, Besançon 25030, France.
| | - Sophie de Bentzmann
- UMR7255-Laboratoire d'Ingénierie des Systèmes Macromoléculaires, CNRS-Aix Marseille University, Marseille 13402, France.
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The AlgZR two-component system recalibrates the RsmAYZ posttranscriptional regulatory system to inhibit expression of the Pseudomonas aeruginosa type III secretion system. J Bacteriol 2013; 196:357-66. [PMID: 24187093 DOI: 10.1128/jb.01199-13] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Pseudomonas aeruginosa causes chronic airway infections in cystic fibrosis (CF) patients. A classic feature of CF airway isolates is the mucoid phenotype. Mucoidy arises through mutation of the mucA anti-sigma factor and subsequent activation of the AlgU regulon. Inactivation of mucA also results in reduced expression of the Vfr transcription factor. Vfr regulates several important virulence factors, including a type III secretion system (T3SS). In the present study, we report that ExsA expression, the master regulator of T3SS gene expression, is further reduced in mucA mutants through a Vfr-independent mechanism involving the RsmAYZ regulatory system. RsmA is an RNA binding protein required for T3SS gene expression. Genetic experiments suggest that the AlgZR two-component system, part of the AlgU regulon, inhibits ExsA expression by increasing the expression of RsmY and RsmZ, two small noncoding RNAs that sequester RsmA from target mRNAs. Epistasis analyses revealed that increasing the concentration of free RsmA, through either rsmYZ deletion or increased RsmA expression, partially restored T3SS gene expression in the mucA mutant. Furthermore, increasing RsmA availability in combination with Vfr complementation fully restored T3SS expression. Recalibration of the RsmAYZ system by AlgZR, however, did not alter the expression of other selected RsmA-dependent targets. We account for this observation by showing that ExsA expression is more sensitive to changes in free RsmA than other members of the RsmA regulon. Together, these data indicate that recalibration of the RsmAYZ system partially accounts for reduced T3SS gene expression in mucA mutants.
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25
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SuhB is a regulator of multiple virulence genes and essential for pathogenesis of Pseudomonas aeruginosa. mBio 2013; 4:e00419-13. [PMID: 24169572 PMCID: PMC3809559 DOI: 10.1128/mbio.00419-13] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
During initial colonization and chronic infection, pathogenic bacteria encounter distinct host environments. Adjusting gene expression accordingly is essential for the pathogenesis. Pseudomonas aeruginosa has evolved complicated regulatory networks to regulate different sets of virulence factors to facilitate colonization and persistence. The type III secretion system (T3SS) and motility are associated with acute infections, while biofilm formation and the type VI secretion system (T6SS) are associated with chronic persistence. To identify novel regulatory genes required for pathogenesis, we screened a P. aeruginosa transposon (Tn) insertion library and found suhB to be an essential gene for the T3SS gene expression. The expression of suhB was upregulated in a mouse acute lung infection model, and loss of suhB resulted in avirulence. Suppression of T3SS gene expression in the suhB mutant is linked to a defective translation of the T3SS master regulator, ExsA. Further studies demonstrated that suhB mutation led to the upregulation of GacA and its downstream small RNAs, RsmY and RsmZ, triggering T6SS expression and biofilm formation while inhibiting the T3SS. Our results demonstrate that an in vivo-inducible gene, suhB, reciprocally regulates genes associated with acute and chronic infections and plays an essential role in the pathogenesis of P. aeruginosa. A variety of bacterial pathogens, such as Pseudomonas aeruginosa, cause acute and chronic infections in humans. During infections, pathogens produce different sets of virulence genes for colonization, tissue damage, and dissemination and for countering host immune responses. Complex regulatory networks control the delicate tuning of gene expression in response to host environments to enable the survival and growth of invading pathogens. Here we identified suhB as a critical gene for the regulation of virulence factors in P. aeruginosa. The expression of suhB was upregulated during acute infection in an animal model, and mutation of suhB rendered P. aeruginosa avirulent. Moreover, we demonstrate that SuhB is required for the activation of virulence factors associated with acute infections while suppressing virulence factors associated with chronic infections. Our report provides new insights into the multilayered regulatory network of virulence genes in P. aeruginosa.
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26
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Heimer SR, Evans DJ, Stern ME, Barbieri JT, Yahr T, Fleiszig SMJ. Pseudomonas aeruginosa utilizes the type III secreted toxin ExoS to avoid acidified compartments within epithelial cells. PLoS One 2013; 8:e73111. [PMID: 24058462 PMCID: PMC3776860 DOI: 10.1371/journal.pone.0073111] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 07/17/2013] [Indexed: 01/06/2023] Open
Abstract
Invasive Pseudomonas aeruginosa (PA) can enter epithelial cells wherein they mediate formation of plasma membrane bleb-niches for intracellular compartmentalization. This phenotype, and capacity for intracellular replication, requires the ADP-ribosyltransferase (ADPr) activity of ExoS, a PA type III secretion system (T3SS) effector protein. Thus, PA T3SS mutants lack these capacities and instead traffic to perinuclear vacuoles. Here, we tested the hypothesis that the T3SS, via the ADPr activity of ExoS, allows PA to evade acidic vacuoles that otherwise suppress its intracellular viability. The acidification state of bacteria-occupied vacuoles within infected corneal epithelial cells was studied using LysoTracker to visualize acidic, lysosomal vacuoles. Steady state analysis showed that within cells wild-type PAO1 localized to both membrane bleb-niches and vacuoles, while both exsA (transcriptional activator) and popB (effector translocation) T3SS mutants were only found in vacuoles. The acidification state of occupied vacuoles suggested a relationship with ExoS expression, i.e. vacuoles occupied by the exsA mutant (unable to express ExoS) were more often acidified than either popB mutant or wild-type PAO1 occupied vacuoles (p < 0.001). An exoS-gfp reporter construct pJNE05 confirmed that high exoS transcriptional output coincided with low occupation of acidified vacuoles, and vice versa, for both popB mutants and wild-type bacteria. Complementation of a triple effector null mutant of PAO1 with exoS (pUCPexoS) reduced the number of acidified bacteria-occupied vacuoles per cell; pUCPexoSE381D which lacks ADPr activity did not. The H+-ATPase inhibitor bafilomycin rescued intracellular replication to wild-type levels for exsA mutants, showing its viability is suppressed by vacuolar acidification. Taken together, the data show that the mechanism by which ExoS ADPr activity allows intracellular replication by PA involves suppression of vacuolar acidification. They also show that variability in ExoS expression by wild-type PA inside cells can differentially influence the fate of individual intracellular bacteria, even within the same cell.
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Affiliation(s)
- Susan R. Heimer
- School of Optometry, University of California, Berkeley, California, United States of America
- College of Pharmacy, Touro University California, Vallejo, California, United States of America
| | - David J. Evans
- School of Optometry, University of California, Berkeley, California, United States of America
- College of Pharmacy, Touro University California, Vallejo, California, United States of America
| | | | - Joseph T. Barbieri
- Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Timothy Yahr
- Department of Microbiology, University of Iowa, Iowa City, Iowa, United States of America
| | - Suzanne M. J. Fleiszig
- School of Optometry, University of California, Berkeley, California, United States of America
- Graduate Groups in Vision Sciences, Microbiology and Infectious Diseases & Immunity, University of California, Berkeley, California, United States of America
- * E-mail:
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27
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Dong YH, Zhang XF, Zhang LH. The global regulator Crc plays a multifaceted role in modulation of type III secretion system in Pseudomonas aeruginosa. Microbiologyopen 2013; 2:161-72. [PMID: 23292701 PMCID: PMC3584221 DOI: 10.1002/mbo3.54] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Revised: 10/29/2012] [Accepted: 11/05/2012] [Indexed: 11/22/2022] Open
Abstract
The opportunistic pathogen Pseudomonas aeruginosa utilizes type III secretion system (T3SS) to translocate effector proteins into eukaryotic host cells that subvert normal host cell functions to the benefit of the pathogen, and results in serious infections. T3SS in P. aeruginosa is controlled by a complex system of regulatory mechanisms and signaling pathways. In this study, we described that Crc, an RNA-binding protein, exerts a positive impact on T3SS in P. aeruginosa, as evidenced by promoter activity assays of several key T3SS genes, transcriptomics, RT-PCR, and immunoblotting in crc mutant. We further demonstrated that the regulatory function of Crc on the T3SS was mediated through the T3SS master regulator ExsA and linked to the Cbr/Crc signaling system. Expression profiling of the crc mutant revealed a downregulation of flagship T3SS genes as well as 16 other genes known to regulate T3SS gene expression in P. aeruginosa. On the basis of these data, we proposed that Crc may exert multifaceted control on the T3SS through various pathways, which may serve to fine-tune this virulence mechanism in response to environmental changes and nutrient sources.
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Affiliation(s)
- Yi-Hu Dong
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Singapore, 138673.
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28
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Diaz MR, King JM, Yahr TL. Intrinsic and Extrinsic Regulation of Type III Secretion Gene Expression in Pseudomonas Aeruginosa. Front Microbiol 2011; 2:89. [PMID: 21833328 PMCID: PMC3153048 DOI: 10.3389/fmicb.2011.00089] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Accepted: 04/13/2011] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that is particularly problematic in the healthcare setting where it is a frequent cause of pneumonia, bloodstream, and urinary tract infections. An important determinant of P. aeruginosa virulence is a type III secretion system (T3SS). T3SS-dependent intoxication is a complex process that minimally requires binding of P. aeruginosa to host cells, injection of the cytotoxic effector proteins through the host cell plasma membrane, and induction of T3SS gene expression. The latter process, referred to as contact-dependent expression, involves a well-characterized regulatory cascade that activates T3SS gene expression in response to host cell contact. Although host cell contact is a primary activating signal for T3SS gene expression, the involvement of multiple membrane-bound regulatory systems indicates that additional environmental signals also play a role in controlling expression of the T3SS. These regulatory systems coordinate T3SS gene expression with many other cellular activities including motility, mucoidy, polysaccharide production, and biofilm formation. The signals to which the organism responds are poorly understood but many seem to be coupled to the metabolic state of the cell and integrated within a master circuit that assimilates informational signals from endogenous and exogenous sources. Herein we review progress toward unraveling this complex circuitry, provide analysis of the current knowledge gaps, and highlight potential areas for future studies. Complete understanding of the regulatory networks that control T3SS gene expression will maximize opportunities for the development of strategies to treat P. aeruginosa infections.
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Affiliation(s)
- Manisha R Diaz
- Department of Microbiology, University of Iowa Iowa City, IA, USA
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29
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Fito-Boncompte L, Chapalain A, Bouffartigues E, Chaker H, Lesouhaitier O, Gicquel G, Bazire A, Madi A, Connil N, Véron W, Taupin L, Toussaint B, Cornelis P, Wei Q, Shioya K, Déziel E, Feuilloley MGJ, Orange N, Dufour A, Chevalier S. Full virulence of Pseudomonas aeruginosa requires OprF. Infect Immun 2011; 79:1176-86. [PMID: 21189321 PMCID: PMC3067511 DOI: 10.1128/iai.00850-10] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Revised: 09/10/2010] [Accepted: 12/02/2010] [Indexed: 01/26/2023] Open
Abstract
OprF is a general outer membrane porin of Pseudomonas aeruginosa, a well-known human opportunistic pathogen associated with severe hospital-acquired sepsis and chronic lung infections of cystic fibrosis patients. A multiphenotypic approach, based on the comparative study of a wild-type strain of P. aeruginosa, its isogenic oprF mutant, and an oprF-complemented strain, showed that OprF is required for P. aeruginosa virulence. The absence of OprF results in impaired adhesion to animal cells, secretion of ExoT and ExoS toxins through the type III secretion system (T3SS), and production of the quorum-sensing-dependent virulence factors pyocyanin, elastase, lectin PA-1L, and exotoxin A. Accordingly, in the oprF mutant, production of the signal molecules N-(3-oxododecanoyl)-l-homoserine lactone and N-butanoyl-l-homoserine lactone was found to be reduced and delayed, respectively. Pseudomonas quinolone signal (PQS) production was decreased, while its precursor, 4-hydroxy-2-heptylquinoline (HHQ), accumulated in the cells. Taken together, these results show the involvement of OprF in P. aeruginosa virulence, at least partly through modulation of the quorum-sensing network. This is the first study showing a link between OprF, PQS synthesis, T3SS, and virulence factor production, providing novel insights into virulence expression.
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Affiliation(s)
- Laurène Fito-Boncompte
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Annelise Chapalain
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Emeline Bouffartigues
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Hichem Chaker
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Olivier Lesouhaitier
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Gwendoline Gicquel
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Alexis Bazire
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Amar Madi
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Nathalie Connil
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Wilfried Véron
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Laure Taupin
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Bertrand Toussaint
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Pierre Cornelis
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Qing Wei
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Koki Shioya
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Eric Déziel
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Marc G. J. Feuilloley
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Nicole Orange
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Alain Dufour
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
| | - Sylvie Chevalier
- Laboratoire de Microbiologie du Froid, Signaux et Micro-Environnement, EA 4312, Normandie Sécurité Sanitaire, Université de Rouen, Rouen, France, Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, Lorient, France, Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute of Biotechnology (VIB), Vrije Universiteit Brussel, Brussels, Belgium, INRS-Institut Armand-Frappier, Laval, Québec, Canada, TIMC-IMAG, TheREx, Thérapeutiques Recombinantes Expérimentales, UMR5525 CNRS-Université Joseph Fourier, Grenoble, France
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The ADP-ribosylation domain of Pseudomonas aeruginosa ExoS is required for membrane bleb niche formation and bacterial survival within epithelial cells. Infect Immun 2010; 78:4500-10. [PMID: 20732998 DOI: 10.1128/iai.00417-10] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Pseudomonas aeruginosa can establish a niche within the plasma membrane of epithelial cells (bleb niches) within which bacteria can survive, replicate, and swim at speeds detectable by real-time phase-contrast imaging. This novel virulence strategy is dependent on the bacterial type three secretion system (T3SS), since mutants lacking the T3SS needle or known T3SS effectors localize to perinuclear vacuoles and fail to replicate. Here, we determined which of the three effectors (ExoS, ExoT, or ExoY) were required for bleb niche formation and intracellular replication. PAO1 strains with mutations in exoS, exoT, exoY, or combinations thereof were compared to wild-type and complemented strains. P. aeruginosa exoS mutants, but not exoT or exoY mutants, lost the capacity for bleb niche formation and intracellular replication. Complementation with exoS rescued both phenotypes, either in the background of an exoS mutant or in a mutant lacking all three known effectors. Complementation with activity domain mutants of exoS revealed that the ADP-ribosyltransferase (ADP-r) activity of ExoS, but not the Rho-GAP activity nor the membrane localization domain (MLD) of ExoS, was required to elicit this phenotype. Membrane bleb niches that contained P. aeruginosa also bound annexin V-enhanced green fluorescent protein (EGFP), a marker of early apoptosis. These data show that P. aeruginosa bleb niches and intracellular survival involve ExoS ADP-r activity and implicate a connection between bleb niche formation and the known role(s) of ExoS-mediated apoptosis and/or Rab GTPase inactivation.
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Kodama T, Yamazaki C, Park KS, Akeda Y, Iida T, Honda T. Transcription of Vibrio parahaemolyticus T3SS1 genes is regulated by a dual regulation system consisting of the ExsACDE regulatory cascade and H-NS. FEMS Microbiol Lett 2010; 311:10-7. [PMID: 20722736 DOI: 10.1111/j.1574-6968.2010.02066.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Vibrio parahaemolyticus, one of the human pathogenic vibrios, causes gastroenteritis, wound infections and septicemia. Genomic sequencing of this organism revealed that it has two distinct type III secretion systems (T3SS1 and T3SS2). T3SS1 plays a significant role in lethal activity in a murine infection model. It was reported that expression of the T3SS1 gene is controlled by a positive regulator, ExsA, and a negative regulator, ExsD, which share a degree of sequence similarity with Pseudomonas aeruginosa ExsA and ExsD, respectively. However, it is unknown whether T3SS1 is regulated by a mechanism similar to that demonstrated for P. aeruginosa, because functional analysis of VP1701, which is homologous to ExsC, is lacking and there is no ExsE homologue in the T3SS1 region. Here, we demonstrate that vp1701 and vp1702 are functional orthologues of exsC and exsE, respectively, of P. aeruginosa. VP1701 was required for the production of T3SS1-related proteins. VP1702 was a negative regulator for T3SS1-related protein production and was secreted by T3SS1. We also found that H-NS represses T3SS1-related gene expression by suppressing exsA gene expression. These findings indicate that the transcription of V. parahaemolyticus T3SS1 genes is regulated by a dual regulatory system consisting of the ExsACDE regulatory cascade and H-NS.
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Affiliation(s)
- Toshio Kodama
- Department of Bacterial Infections, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan.
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Vogelaar NJ, Jing X, Robinson HH, Schubot FD. Analysis of the crystal structure of the ExsC.ExsE complex reveals distinctive binding interactions of the Pseudomonas aeruginosa type III secretion chaperone ExsC with ExsE and ExsD. Biochemistry 2010; 49:5870-9. [PMID: 20536183 DOI: 10.1021/bi100432e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Pseudomonas aeruginosa, like many Gram-negative bacterial pathogens, requires its type III secretion system (T3SS) to facilitate acute infections. In P. aeruginosa, the expression of all T3SS-related genes is regulated by the transcriptional activator ExsA. A signaling cascade involving ExsA and three additional proteins, ExsC, ExsD, and ExsE, directly ties the upregulation of ExsA-mediated transcription to the activation of the type III secretion apparatus. In order to characterize the events underlying the signaling process, the crystal structure of the T3SS chaperone ExsC in complex with its cognate effector ExsE has been determined. The structure reveals critical contacts that mediate the interactions between these two proteins. Particularly striking is the presence of two Arg-X-Val-X-Arg motifs in ExsE that form identical interactions along opposite sides of an ExsC dimer. The structure also provides insights into the interactions of ExsC with the antiactivator protein ExsD. It was shown that the amino-terminal 46 residues of ExsD are sufficient for ExsC binding. On the basis of these findings, a new model for the ExsC.ExsD complex is proposed to explain its distinctive 2:2 stoichiometry and why ExsC displays a weaker affinity for ExsD than for ExsE.
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Affiliation(s)
- Nancy J Vogelaar
- Department of Biological Sciences, Life Science I, Virginia Polytechnic Institute and State University, Washington Street, Blacksburg, Virginia 24060, USA
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Lee PC, Stopford CM, Svenson AG, Rietsch A. Control of effector export by the Pseudomonas aeruginosa type III secretion proteins PcrG and PcrV. Mol Microbiol 2010; 75:924-41. [PMID: 20487288 DOI: 10.1111/j.1365-2958.2009.07027.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Pseudomonas aeruginosa uses a type III secretion system to inject protein effectors into a targeted host cell. Effector secretion is triggered by host cell contact. How effector secretion is prevented prior to cell contact is not well understood. In all secretion systems studied to date, the needle tip protein is required for controlling effector secretion, but the mechanism by which needle tip proteins control effector secretion is unclear. Here we present data that the P. aeruginosa needle tip protein, PcrV, controls effector secretion by assembling into a functional needle tip complex. PcrV likely does not simply obstruct the secretion channel because the pore-forming translocator proteins can still be secreted while effector secretion is repressed. This finding suggests that PcrV controls effector secretion by affecting the conformation of the apparatus, shifting it from the default, effector secretion 'on' conformation, to the effector secretion 'off' conformation. We also present evidence that PcrG, which can bind to PcrV and is also involved in controlling effector export, is cytoplasmic and that the interaction between PcrG and PcrV is not required for effector secretion control by either protein. Taken together, these data allow us to propose a working model for control of effector secretion by PcrG and PcrV.
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Affiliation(s)
- Pei-Chung Lee
- Department of Molecular Biology and Microbiology, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106-4960, USA
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Zhou X, Konkel ME, Call DR. Regulation of type III secretion system 1 gene expression in Vibrio parahaemolyticus is dependent on interactions between ExsA, ExsC, and ExsD. Virulence 2010; 1:260-72. [PMID: 21178451 PMCID: PMC3073295 DOI: 10.4161/viru.1.4.12318] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Revised: 04/22/2010] [Accepted: 04/23/2010] [Indexed: 01/12/2023] Open
Abstract
Vibrio parahaemolyticus ExsA is the transcriptional regulator for type III secretion system 1 (T3SS1) while ExsD blocks T3SS1 expression. Herein we show that deletion of exsC from V. parahaemolyticus blocked synthesis of T3SS1-dependent proteins under inducing conditions (contact with HeLa cells), while in trans complementation of the ΔexsC strain with wild-type exsC restored protein synthesis. Under non-inducing conditions (Luria broth plus salt), in trans expression of exsC in a wild-type strain resulted in synthesis and secretion of T3SS1-dependent proteins. Deletion of exsC does not affect the synthesis of ExsA while expression of T3SS1 genes is independent of ExsC in the absence of ExsD. Co-expression of recombinant proteins with different antigenic tags demonstrated that ExsC binds ExsD and that the N-terminal amino acids of ExsC (positions 7 to 12) are required for binding. Co-expression and purification of antigentically tagged ExsA and ExsD demonstrated that ExsD directly binds ExsA and presumably prevents ExsA from binding promoter regions of T3SS1 genes. Collectively these data demonstrate that ExsD binds ExsA to block expression of T3SS1 genes, while ExsC binds ExsD to permit expression of T3SS1 genes. ExsA, ExsC, and ExsD from V. parahaemolyticus appear to be functional orthologues of their Pseudomonas aeruginosa counterparts.
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Affiliation(s)
- Xiaohui Zhou
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA
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Control of the type 3 secretion system in Vibrio harveyi by quorum sensing through repression of ExsA. Appl Environ Microbiol 2010; 76:4996-5004. [PMID: 20543047 DOI: 10.1128/aem.00886-10] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The type 3 secretion system (T3SS) genes of Vibrio harveyi are activated at low cell density and repressed at high cell density by quorum sensing (QS). Repression requires LuxR, the master transcriptional regulator of QS-controlled genes. Here, we determine the mechanism underlying the LuxR repression of the T3SS system. Using a fluorescence-based cell sorting approach, we isolated V. harveyi mutants that are unable to express T3SS genes at low cell density and identified two mutations in the V. harveyi exsBA operon. While LuxR directly represses the expression of exsBA, complementation and epistasis analyses reveal that it is the repression of exsA expression, but not exsB expression, that is responsible for the QS-mediated repression of T3SS genes at high cell density. The present work further defines the genes in the V. harveyi QS regulon and elucidates a mechanism demonstrating how multiple regulators can be linked in series to direct the expression of QS target genes specifically at low or high cell density.
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ExsA recruits RNA polymerase to an extended -10 promoter by contacting region 4.2 of sigma-70. J Bacteriol 2010; 192:3597-607. [PMID: 20453093 DOI: 10.1128/jb.00129-10] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
ExsA is a member of the AraC family of transcriptional activators and is required for expression of the Pseudomonas aeruginosa type III secretion system (T3SS). ExsA-dependent promoters consist of two binding sites for monomeric ExsA located approximately 50 bp upstream of the transcription start sites. Binding to both sites is required for recruitment of sigma(70)-RNA polymerase (RNAP) to the promoter. ExsA-dependent promoters also contain putative -35 hexamers that closely match the sigma(70) consensus but are atypically spaced 21 or 22 bp from the -10 hexamer. Because several nucleotides located within the putative -35 region are required for ExsA binding, it is unclear whether the putative -35 region makes an additional contribution to transcription initiation. In the present study we demonstrate that the putative -35 hexamer is dispensable for ExsA-independent transcription from the P(exsC) promoter and that deletion of sigma(70) region 4.2, which contacts the -35 hexamer, has no effect on ExsA-independent transcription from P(exsC). Region 4.2 of sigma(70), however, is required for ExsA-dependent activation of the P(exsC) and P(exsD) promoters. Genetic data suggest that ExsA directly contacts region 4.2 of sigma(70), and several amino acids were found to contribute to the interaction. In vitro transcription assays demonstrate that an extended -10 element located in the P(exsC) promoter is important for overall promoter activity. Our collective data suggest a model in which ExsA compensates for the lack of a -35 hexamer by interacting with region 4.2 of sigma(70) to recruit RNAP to the promoter.
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Abstract
ExsA is a transcriptional activator of the Pseudomonas aeruginosa type III secretion system (T3SS). The T3SS consists of >40 genes organized within 10 transcriptional units, each of which is controlled by the transcriptional activator ExsA. ExsA-dependent promoters contain two adjacent ExsA binding sites that when occupied protect the -30 to -70 region from DNase I cleavage. The promoters also possess regions bearing strong resemblance to the consensus -10 and -35 regions of sigma(70)-dependent promoters. The spacing distance between the putative -10 and -35 regions of ExsA-dependent promoters, however, is increased by 4 to 5 bp compared to that in typical sigma(70)-dependent promoters. In the present study, we demonstrate that ExsA-dependent transcriptional activation requires a 21- or 22-bp spacer length between the -10 and -35 regions. Despite the atypical spacing in this region, in vitro transcription assays using sigma(70)-saturated RNA polymerase holoenzyme (RNAP-sigma(70)) confirm that ExsA-dependent promoters are indeed sigma(70) dependent. Potassium permanganate footprinting experiments indicate that ExsA facilitates an early step in transcriptional initiation. Although RNAP-sigma(70) binds to the promoters with low affinity in the absence of ExsA, the activator stimulates transcription by enhancing recruitment of RNAP-sigma(70) to the P(exsC) and P(exsD) promoters. Abortive initiation assays confirm that ExsA enhances the equilibrium binding constant for RNAP while having only a modest effect on the isomerization rate constant.
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Bernhards RC, Jing X, Vogelaar NJ, Robinson H, Schubot FD. Structural evidence suggests that antiactivator ExsD from Pseudomonas aeruginosa is a DNA binding protein. Protein Sci 2009; 18:503-13. [PMID: 19235906 DOI: 10.1002/pro.48] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The opportunistic pathogen P. aeruginosa utilizes a type III secretion system (T3SS) to support acute infections in predisposed individuals. In this bacterium, expression of all T3SS-related genes is dependent on the AraC-type transcriptional activator ExsA. Before host contact, the T3SS is inactive and ExsA is repressed by the antiactivator protein ExsD. The repression, thought to occur through direct interactions between the two proteins, is relieved upon opening of the type III secretion (T3S) channel when secretion chaperone ExsC sequesters ExsD. We have solved the crystal structure of Delta20ExsD, a protease-resistant fragment of ExsD that lacks only the 20 amino terminal residues of the wild-type protein at 2.6 A. Surprisingly the structure revealed similarities between ExsD and the DNA binding domain of transcriptional repressor KorB. A model of an ExsD-DNA complex constructed on the basis of this homology produced a realistic complex that is supported by the prevalence of conserved residues in the putative DNA binding site and the results of differential scanning fluorimetry studies. Our findings challenge the currently held model that ExsD solely acts through interactions with ExsA and raise new questions with respect to the underlying mechanism of ExsA regulation.
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Affiliation(s)
- Robert C Bernhards
- Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24060, USA
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Functional domains of ExsA, the transcriptional activator of the Pseudomonas aeruginosa type III secretion system. J Bacteriol 2009; 191:3811-21. [PMID: 19376850 DOI: 10.1128/jb.00002-09] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The opportunistic pathogen Pseudomonas aeruginosa utilizes a type III secretion system (T3SS) to evade phagocytosis and damage eukaryotic cells. Transcription of the T3SS regulon is controlled by ExsA, a member of the AraC/XylS family of transcriptional regulators. These family members generally consist of an approximately 100-amino acid carboxy-terminal domain (CTD) with two helix-turn-helix DNA binding motifs and an approximately 200-amino acid amino-terminal domain (NTD) with known functions including oligomerization and ligand binding. In the present study, we show that the CTD of ExsA binds to ExsA-dependent promoters in vitro and activates transcription from ExsA-dependent promoters both in vitro and in vivo. Despite possessing these activities, the CTD lacks the cooperative binding properties observed for full-length ExsA at the P(exsC) promoter. In addition, the CTD is unaffected by the negative regulatory activity of ExsD, an inhibitor of ExsA activity. Binding studies confirm that ExsD interacts directly with the NTD of ExsA. Our data are consistent with a model in which a single ExsA molecule first binds to a high-affinity site on the P(exsC) promoter. Protein-protein interactions mediated by the NTD then recruit an additional ExsA molecule to a second site on the promoter to form a complex capable of stimulating wild-type levels of transcription. These findings provide important insight into the mechanisms of transcriptional activation by ExsA and inhibition of ExsA activity by ExsD.
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Shen DK, Filopon D, Chaker H, Boullanger S, Derouazi M, Polack B, Toussaint B. High-cell-density regulation of the Pseudomonas aeruginosa type III secretion system: implications for tryptophan catabolites. MICROBIOLOGY-SGM 2008; 154:2195-2208. [PMID: 18667553 DOI: 10.1099/mic.0.2007/013680-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The Pseudomonas aeruginosa type III secretion system (T3SS) is known to be a very important virulence factor in acute human infections, but it is less important in maintaining chronic infections in which T3SS genes are downregulated. In vitro, the activation of T3SS expression involves a positive activating loop that acts on the transcriptional regulator ExsA. We have observed that in vivo T3SS expression is cell density-dependent in a manner that does not need known quorum-sensing (QS) signals. In addition, stationary-phase culture supernatants added to exponential-phase growing strains can inhibit T3SS expression. The analysis of transposon insertion mutants showed that the production of such T3SS-inhibiting signals might depend on tryptophan synthase and hence tryptophan, which is the precursor of signalling molecules such as indole-3-acetic acid (IAA), kynurenine and Pseudomonas quinolone signal (PQS). Commercially available tryptophan-derived molecules were tested for their role in the regulation of T3SS expression. At millimolar concentrations, IAA, 1-naphthalacetic acid (NAA) and 3-hydroxykynurenine inhibited T3SS expression. Inactivation of the tryptophan dioxygenase-encoding kynA gene resulted in a decrease in the T3SS-inhibiting activity of supernatants. These observations suggest that tryptophan catabolites are involved in the downregulation of T3SS expression in the transition from a low- to a high-cell-density state.
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Affiliation(s)
- Da-Kang Shen
- Department of Microbiology and Parasitology, Shanghai Jiao-Tong University School of Medicine, Shanghai 200025, PR China.,GREPI, TIMC-IMAG, UMR5525 CNRS/Université Joseph Fourier Faculté de Médecine, Bat. J Roget, Domaine de la Merci, 38700 La Tronche, France
| | - Didier Filopon
- GREPI, TIMC-IMAG, UMR5525 CNRS/Université Joseph Fourier Faculté de Médecine, Bat. J Roget, Domaine de la Merci, 38700 La Tronche, France
| | - Hichem Chaker
- GREPI, TIMC-IMAG, UMR5525 CNRS/Université Joseph Fourier Faculté de Médecine, Bat. J Roget, Domaine de la Merci, 38700 La Tronche, France
| | - Stephanie Boullanger
- Service Spectrométrie de Masse, CERMAV-CNRS, BP53, 38041 Grenoble cedex 9, France
| | - Madiha Derouazi
- GREPI, TIMC-IMAG, UMR5525 CNRS/Université Joseph Fourier Faculté de Médecine, Bat. J Roget, Domaine de la Merci, 38700 La Tronche, France
| | - Benoit Polack
- GREPI, TIMC-IMAG, UMR5525 CNRS/Université Joseph Fourier Faculté de Médecine, Bat. J Roget, Domaine de la Merci, 38700 La Tronche, France
| | - Bertrand Toussaint
- GREPI, TIMC-IMAG, UMR5525 CNRS/Université Joseph Fourier Faculté de Médecine, Bat. J Roget, Domaine de la Merci, 38700 La Tronche, France
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41
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Zhou X, Shah DH, Konkel ME, Call DR. Type III secretion system 1 genes in Vibrio parahaemolyticus are positively regulated by ExsA and negatively regulated by ExsD. Mol Microbiol 2008; 69:747-64. [PMID: 18554322 PMCID: PMC2610376 DOI: 10.1111/j.1365-2958.2008.06326.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Vibrio parahaemolyticus harbours two distinct type III secretion systems (T3SS1 and T3SS2). A subset of 10 T3SS1 genes are transcribed when V. parahaemolyticus is grown in tissue culture medium [Dulbecco's modified Eagle's medium (DMEM)], while transcription of these genes (except exsD) is minimal upon growth in Luria-Bertani-Salt (LB-S). Transcription of T3SS1 genes and cytotoxicity towards HeLa cells was prevented by deletion of exsA while complementation with exsA restored these traits. Overexpression of ExsA in the wild-type strain, NY-4, activated the transcription of T3SS1 genes when bacteria were grown in LB-S. Thus, ExsA is necessary and sufficient to induce the transcription of T3SS1 genes. Deletion of the exsD permitted the transcription of T3SS1 genes when bacteria were grown in the LB-S medium and complementation with the wild-type exsD gene-blocked transcription of T3SS1 genes. Overexpression of ExsD in NY-4 prevented the transcription of T3SS1 gene when bacteria were grown in DMEM. A gel mobility shift assay demonstrated that purified ExsA protein binds a novel motif in the upstream region of vp1668 and vp1687, indicating that ExsA interacts directly with the promoter sequences of T3SS1 genes. ExsA positively regulates the expression and secretion of Vp1656 while ExsD negatively regulates the expression and secretion of Vp1656.
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Affiliation(s)
- Xiaohui Zhou
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, U.S.A
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42
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Brutinel ED, Vakulskas CA, Brady KM, Yahr TL. Characterization of ExsA and of ExsA-dependent promoters required for expression of the Pseudomonas aeruginosa type III secretion system. Mol Microbiol 2008; 68:657-71. [PMID: 18373522 DOI: 10.1111/j.1365-2958.2008.06179.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Expression of the Pseudomonas aeruginosa type III secretion system (T3SS) is activated by ExsA, a member of the AraC/XylS family of transcriptional regulators. In the present study we examine the DNA-binding properties of ExsA. ExsA was purified as a histidine-tagged fusion protein (ExsA(His)) and found to be monomeric in solution. ExsA(His) specifically bound T3SS promoters with high affinity as determined by electrophoretic mobility shift assays (EMSA). For each promoter tested two distinct ExsA-DNA complexes were detected. Biochemical analyses indicate that the higher-mobility complex consists of a single ExsA(His) molecule bound to DNA while the lower-mobility complex results from the binding of two ExsA(His) molecules. DNase I protection assays demonstrate that the ExsA(His) binding site overlaps the -35 RNA polymerase binding site and extends upstream an additional approximately 34 bp. An alignment of all 10 ExsA-dependent promoters revealed a number of highly conserved nucleotides within the footprinted region. We find that most of the highly conserved nucleotides are required for transcription in vivo; EMSA-binding assays confirm that several of these nucleotides are essential determinants of ExsA(His) binding. The combined data support a model in which two ExsA(His) molecules bind adjacent sites on the promoter to activate T3SS gene transcription.
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Affiliation(s)
- Evan D Brutinel
- Department of Microbiology, University of Iowa, lowa, IA, USA
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43
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Urbanowski ML, Brutinel ED, Yahr TL. Translocation of ExsE into Chinese hamster ovary cells is required for transcriptional induction of the Pseudomonas aeruginosa type III secretion system. Infect Immun 2007; 75:4432-9. [PMID: 17635873 PMCID: PMC1951186 DOI: 10.1128/iai.00664-07] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Transcription of the Pseudomonas aeruginosa type III secretion system (T3SS) is induced under Ca(2+)-limiting growth conditions or following the contact of the bacteria with host cells. The regulatory response to low Ca(2+) levels is initiated by the T3SS-mediated secretion of ExsE, a negative regulatory protein that prevents T3SS gene transcription. In the present study, we demonstrated that ExsE plays an analogous role in transcriptional induction following host cell contact. By using a flow cytometry assay, the host contact-dependent induction of T3SS gene expression was found to be dependent upon the presence of functional type III translocation machinery. Using three independent assays, we demonstrated that ExsE was translocated into Chinese hamster ovary cells in a T3SS-dependent manner. Deletion mapping experiments indicated that the amino terminus of ExsE is required both for secretion under Ca(2+)-limiting growth conditions and for translocation into host cells. A P. aeruginosa mutant expressing an exsE allele lacking codons 3 through 20 was deficient in ExsE secretion and translocation and showed constitutive repression of T3SS gene expression under Ca(2+)-limiting growth conditions. The mutant also failed to induce T3SS gene expression following host cell contact and demonstrated a significant reduction in T3SS-dependent cytotoxicity towards Chinese hamster ovary cells, indicating that the translocation of ExsE is required for the host contact-dependent induction of T3SS gene expression.
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Affiliation(s)
- Mark L Urbanowski
- Department of Microbiology, 540B EMRB, University of Iowa, Iowa City, IA 52242, USA
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Linares JF, Gustafsson I, Baquero F, Martinez JL. Antibiotics as intermicrobial signaling agents instead of weapons. Proc Natl Acad Sci U S A 2006; 103:19484-9. [PMID: 17148599 PMCID: PMC1682013 DOI: 10.1073/pnas.0608949103] [Citation(s) in RCA: 459] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
It has been widely assumed that the ecological function of antibiotics in nature is fighting against competitors. This made them a good example of the Darwinian struggle-for-life in the microbial world. Based on this idea, it also has been believed that antibiotics, even at subinhibitory concentrations, reduce virulence of bacterial pathogens. Herein, using a combination of genomic and functional assays, we demonstrate that specific antibiotics (namely tobramycin, tetracycline, and norfloxacin) at subinhibitory concentrations trigger expression of determinants influencing the virulence of the major opportunistic bacterial pathogen Pseudomonas aeruginosa. All three antibiotics induce biofilm formation; tobramycin increases bacterial motility, and tetracycline triggers expression of P. aeruginosa type III secretion system and consequently bacterial cytotoxicity. Besides their relevance in the infection process, those determinants are relevant for the ecological behavior of this bacterial species in natural, nonclinical environments, either by favoring colonization of surfaces (biofilm, motility) or for fighting against eukaryotic predators (cytotoxicity). Our results support the notion that antibiotics are not only bacterial weapons for fighting competitors but also signaling molecules that may regulate the homeostasis of microbial communities. At low concentrations, they can even be beneficial for the behavior of susceptible bacteria in natural environments. This is a complete change on our vision on the ecological function of antibiotics with clear implications both for the treatment of infectious diseases and for the understanding of the microbial relationships in the biosphere.
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Affiliation(s)
- J. F. Linares
- *Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, Darwin 3, Campus Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| | - I. Gustafsson
- *Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, Darwin 3, Campus Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
- Clinical Microbiology, County Hospital, SE-301 85 Halmstad, Sweden; and
| | - F. Baquero
- Unidad Asociada al Centro Nacional de Biotecnología “Resistencia a los Antibióticos y Virulencia Bacteriana,” Departamento de Microbiología, Hospital Ramón y Cajal, 28034 Madrid, Spain
| | - J. L. Martinez
- *Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, Darwin 3, Campus Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
- To whom correspondence should be addressed. E-mail:
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45
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Lykken GL, Chen G, Brutinel ED, Chen L, Yahr TL. Characterization of ExsC and ExsD self-association and heterocomplex formation. J Bacteriol 2006; 188:6832-40. [PMID: 16980486 PMCID: PMC1595525 DOI: 10.1128/jb.00884-06] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Expression of the Pseudomonas aeruginosa type III secretion system (T3SS) is induced by calcium depletion and is positively regulated by the ExsA transcriptional activator and negatively regulated by the ExsD antiactivator. Under conditions permissive for expression of the T3SS, the negative regulatory activity of ExsD is antagonized by a direct binding interaction with ExsC. In the present study, the ExsC-ExsD binding interaction was characterized. Individually, both ExsC and ExsD form self-associated complexes, as judged by bacterial monohybrid and gel filtration experiments. A mixture of purified ExsC and ExsD readily formed a complex that elutes from gel filtration medium as a single included peak. The calculated molecular weight of the ExsC-ExsD complex is consistent with a complex containing multiple copies of ExsC and ExsD. Isothermic titration calorimetry experiments found formation of the ExsC-ExsD complex to be thermodynamically favorable, with a Kd of approximately 18 nM and a likely binding ratio of 1:1. To identify amino acid residues important for the regulatory activities of ExsC and ExsD, self-association, and complex formation, charged-cluster mutagenesis was performed. Two of the resulting ExsD charged-cluster mutants (DM2 and DM3) demonstrated a hyperrepressive phenotype for expression of the T3SS. By two-hybrid and copurification assays, the DM3 mutant was found to be impaired in its interaction with ExsC. This finding demonstrates that the binding of ExsC to ExsD is required for transcriptional induction of the T3SS under calcium-limiting growth conditions.
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Affiliation(s)
- Guinevere L Lykken
- Department of Microbiology, University of Iowa, Iowa City, IA 52242-1101, USA
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46
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Abstract
Type III secretion systems (T3SS) function by translocating effector proteins into eukaryotic host cells and are important for the virulence of many Gram-negative bacterial pathogens. Although the secretion and translocation machineries are highly conserved between different species, each pathogen translocates a unique set of effectors that subvert normal host cell physiology to promote pathogenesis. The uniqueness of each pathogen is further reflected in the diversity of mechanisms used to regulate T3SS gene expression. Pseudomonas aeruginosa utilizes a complex set of signalling pathways to modulate T3SS expression in response to extracellular and intracellular cues. Whereas some pathways are dedicated solely to regulating the T3SS, others co-ordinately regulate expression of the T3SS with multiple virulence functions on a global scale. Emerging regulatory themes include coupling of T3SS transcription with type III secretory activity, global regulatory control through modulation of cAMP biosynthesis, repression by a variety of stresses, involvement of multiple two component regulatory systems, and an inverse relationship between T3SS expression and multicellular behaviour. Factors controlling activation of T3SS expression likely contribute to the environmental survival of the organism and to the pathogenesis of acute P. aeruginosa infections. Conversely, active repression of the T3SS might contribute to the persistence of chronic infections.
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Affiliation(s)
- Timothy L Yahr
- University of Iowa, Department of Microbiology, Iowa City, IA, USA.
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Shen DK, Filopon D, Kuhn L, Polack B, Toussaint B. PsrA is a positive transcriptional regulator of the type III secretion system in Pseudomonas aeruginosa. Infect Immun 2006; 74:1121-9. [PMID: 16428760 PMCID: PMC1360315 DOI: 10.1128/iai.74.2.1121-1129.2006] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The type III secretion system (TTSS) of Pseudomonas aeruginosa is induced in vivo upon contact with eukaryotic cells and in vitro by calcium depletion in culture medium. We have observed a previously identified protein, PsrA, necessary for full activation of TTSS gene expression in P. aeruginosa. Electrophoretic mobility shift assays showed that recombinant PsrA could bind to the exsCEBA promoter region. A mutant with a deletion in the psrA gene was constructed. Using transcriptional fusions, we demonstrated that PsrA is required for the full activation of transcription of the TTSS regulatory operon exsCEBA and effector exoS, although the deletion mutant still responded to calcium depletion, to serum, and to host cell contact. The psrA mutant showed a marked decrease in the secretion of the type III effectors and weak resistance to phagocyte-like PLB-985 cells. The defect in TTSS transcription and secretion in the psrA mutant could be complemented by expression in trans of psrA. PsrA was previously identified as a transcriptional activator of RpoS, a central regulator during stationary phase. We confirmed with our strain that RpoS has a negative effect on TTSS gene expression. Taken altogether, these results suggest that PsrA is a newly identified activator that is involved in the expression of the TTSS by enhancing the exsCEBA transcriptional level.
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Affiliation(s)
- D K Shen
- GREPI EA2938, DBPC/Enzymologie, CHU-Grenoble BP217, 38043, Grenoble cedex 9, France
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48
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Kim J, Ahn K, Min S, Jia J, Ha U, Wu D, Jin S. Factors triggering type III secretion in Pseudomonas aeruginosa. MICROBIOLOGY-SGM 2005; 151:3575-3587. [PMID: 16272380 DOI: 10.1099/mic.0.28277-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The type III secretion system of Pseudomonas aeruginosa is tightly regulated by various environmental signals, such as low calcium and contact with the host cell. However, the exact signals triggering type III secretion are unknown. The present study describes the finding that secretion of P. aeruginosa type III effector molecules requires protein factors from serum and L broth, designated type III secretion factors (TSFs), in addition to the low-calcium environment. In the absence of TSF or calcium chelator EGTA, basal levels of type III effector molecules are accumulated intracellularly. Addition of TSF and EGTA together effectively triggers the secretion of pre-existing effector molecules in a short time, even before the active expression of type III genes; thus, active type III gene expression does not seem to be a prerequisite for type III secretion. A search for TSF molecules in serum and L broth resulted in the identification of albumin and casein as the functional TSF molecules. Although there is no clear sequence similarity between albumin and casein, both proteins are known to have a low-affinity, high-capacity calcium-binding property. Tests of well-studied calcium-binding proteins seemed to indicate that low-affinity calcium-binding proteins have TSF activity, although the requirement of low-affinity calcium-binding ability for the TSF activity is not clear. P. aeruginosa seems to have evolved a sensing mechanism to detect target cells for type III injection through host-derived proteins in combination with a low-calcium signal. Disruption of the bacterial ability to sense low calcium or TSF might be a valid avenue to the effective control of this bacterial pathogen.
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Affiliation(s)
- Jaewha Kim
- Department of Molecular Genetics and Microbiology, PO Box 100266, University of Florida, Gainesville, FL 32610, USA
| | - Kyungseop Ahn
- Department of Molecular Genetics and Microbiology, PO Box 100266, University of Florida, Gainesville, FL 32610, USA
| | - Sungran Min
- Department of Molecular Genetics and Microbiology, PO Box 100266, University of Florida, Gainesville, FL 32610, USA
| | - Jinghua Jia
- Department of Molecular Genetics and Microbiology, PO Box 100266, University of Florida, Gainesville, FL 32610, USA
| | - Unhwan Ha
- Department of Molecular Genetics and Microbiology, PO Box 100266, University of Florida, Gainesville, FL 32610, USA
| | - Donghai Wu
- Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, Guangzhou, China
| | - Shouguang Jin
- Department of Molecular Genetics and Microbiology, PO Box 100266, University of Florida, Gainesville, FL 32610, USA
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Bröms JE, Edqvist PJ, Carlsson KE, Forsberg A, Francis MS. Mapping of a YscY binding domain within the LcrH chaperone that is required for regulation of Yersinia type III secretion. J Bacteriol 2005; 187:7738-52. [PMID: 16267298 PMCID: PMC1280294 DOI: 10.1128/jb.187.22.7738-7752.2005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Type III secretion systems are used by many animal and plant interacting bacteria to colonize their host. These systems are often composed of at least 40 genes, making their temporal and spatial regulation very complex. Some type III chaperones of the translocator class are important regulatory molecules, such as the LcrH chaperone of Yersinia pseudotuberculosis. In contrast, the highly homologous PcrH chaperone has no regulatory effect in native Pseudomonas aeruginosa or when produced in Yersinia. In this study, we used LcrH-PcrH chaperone hybrids to identify a discrete region in the N terminus of LcrH that is necessary for YscY binding and regulatory control of the Yersinia type III secretion machinery. PcrH was unable to bind YscY and the homologue Pcr4 of P. aeruginosa. YscY and Pcr4 were both essential for type III secretion and reciprocally bound to both substrates YscX of Yersinia and Pcr3 of P. aeruginosa. Still, Pcr4 was unable to complement a DeltayscY null mutant defective for type III secretion and yop-regulatory control in Yersinia, despite the ability of YscY to function in P. aeruginosa. Taken together, we conclude that the cross-talk between the LcrH and YscY components represents a strategic regulatory pathway specific to Yersinia type III secretion.
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Affiliation(s)
- Jeanette E Bröms
- Department of Medical Countermeasures, Swedish Defence Research Agency, Umeå
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50
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Saliba AM, de Assis MC, Nishi R, Raymond B, Marques EDA, Lopes UG, Touqui L, Plotkowski MC. Implications of oxidative stress in the cytotoxicity of Pseudomonas aeruginosa ExoU. Microbes Infect 2005; 8:450-9. [PMID: 16293434 DOI: 10.1016/j.micinf.2005.07.011] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Revised: 07/15/2005] [Accepted: 07/19/2005] [Indexed: 11/23/2022]
Abstract
ExoU PLA2-like activity has been shown to account for membrane lysis and acute death of infected cells. Translocation of effector proteins by the type III secretion systems depends on close contact between microbial and host cells. Our finding that both the ExoU-producing PA103 Pseudomonas aeruginosa and its mutant obtained by deletion of exoU adhered poorly to endothelial cells (EC) led to the hypothesis that, in some cells, the amount of injected toxin may not be enough to induce cell lysis but cells would suffer from a long-term effect of ExoU intoxication. To address this question, cells were exposed to both bacteria for 1 h and then treated with gentamicin-containing medium, to eliminate infecting microorganisms. After 24 h, the percentage of viable EC in PA103-infected cultures was significantly lower than in cultures exposed to the mutant, as determined by the MTT assay. Cell death was not likely to depend on the ExoU lytic activity since cell labeling with propidium iodide was similar in cultures infected with both bacterial strains. Bacterial cytotoxicity was significantly reduced by MAFP, a specific inhibitor of cPLA2 and iPLA2. Since the PLA2 activity on membrane phospholipids generates free fatty acid, including arachidonic acid (AA), we next compared the bacterial ability to release AA from infected EC. PA103 was shown to induce a potent AA release that was inhibited by MAFP. AA oxidation by oxygenases generates eicosanoids, known to induce both cell death and proliferation. However neither inhibitors of cyclooxygenases (ibuprofen) nor lipoxygenases (NDGA) reduced the ExoU toxicity. Since non-enzymatic oxidation of AA generates reactive radicals, we next investigated the PA103 ability to induce oxidative stress in infected cells. FACS analysis of cell labeling with the C-11 fluor probe and with anti-4-hydroxynonel antibody revealed a significant peroxidation of cell membrane lipids. These results, together with our finding that PA103-infected EC death was significantly attenuated by alpha-tocopherol, led to the conclusion that AA-induced oxidative stress may be another mechanism of cell damage in the course of infection by ExoU-producing P. aeruginosa.
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Affiliation(s)
- Alessandra M Saliba
- Department of Microbiology and Immunology, State University of Rio de Janeiro, FCM/UERJ, 551-030 Rio de Janeiro, Brazil
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