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Wu W, Huang J, Xu Z. Antibiotic influx and efflux in Pseudomonas aeruginosa: Regulation and therapeutic implications. Microb Biotechnol 2024; 17:e14487. [PMID: 38801351 PMCID: PMC11129675 DOI: 10.1111/1751-7915.14487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 05/06/2024] [Accepted: 05/09/2024] [Indexed: 05/29/2024] Open
Abstract
Pseudomonas aeruginosa is a notorious multidrug-resistant pathogen that poses a serious and growing threat to the worldwide public health. The expression of resistance determinants is exquisitely modulated by the abundant regulatory proteins and the intricate signal sensing and transduction systems in this pathogen. Downregulation of antibiotic influx porin proteins and upregulation of antibiotic efflux pump systems owing to mutational changes in their regulators or the presence of distinct inducing molecular signals represent two of the most efficient mechanisms that restrict intracellular antibiotic accumulation and enable P. aeruginosa to resist multiple antibiotics. Treatment of P. aeruginosa infections is extremely challenging due to the highly inducible mechanism of antibiotic resistance. This review comprehensively summarizes the regulatory networks of the major porin proteins (OprD and OprH) and efflux pumps (MexAB-OprM, MexCD-OprJ, MexEF-OprN, and MexXY) that play critical roles in antibiotic influx and efflux in P. aeruginosa. It also discusses promising therapeutic approaches using safe and efficient adjuvants to enhance the efficacy of conventional antibiotics to combat multidrug-resistant P. aeruginosa by controlling the expression levels of porins and efflux pumps. This review not only highlights the complexity of the regulatory network that induces antibiotic resistance in P. aeruginosa but also provides important therapeutic implications in targeting the inducible mechanism of resistance.
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Affiliation(s)
- Weiyan Wu
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research CentreSouth China Agricultural UniversityGuangzhouChina
| | - Jiahui Huang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research CentreSouth China Agricultural UniversityGuangzhouChina
| | - Zeling Xu
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research CentreSouth China Agricultural UniversityGuangzhouChina
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Feng Q, Zhou J, Zhang L, Fu Y, Yang L. Insights into the molecular basis of c-di-GMP signalling in Pseudomonas aeruginosa. Crit Rev Microbiol 2024; 50:20-38. [PMID: 36539391 DOI: 10.1080/1040841x.2022.2154140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 11/25/2022] [Indexed: 12/24/2022]
Abstract
The opportunistic human pathogen Pseudomonas aeruginosa can cause severe infections in immunocompromized people or cystic fibrosis (CF) patients. Because of its remarkable ability to invade the host and withstand the bacteriocidal effect of most conventional antibiotics, the infection caused by P. aeruginosa has become a major concern for human health. The switch from acute to chronic infection is governed by the second messenger bis-(3'-5')-cyclic dimeric guanosine mono-phosphate (c-di-GMP) in P. aeruginosa, and c-di-GMP is now recognized to regulate many important biological processes in pathogenesis. The c-di-GMP signalling mechanisms in P. aeruginosa have been studied extensively in the past decade, revealing complicated c-di-GMP metabolism and signalling network. In this review, the underlying mechanisms of this signalling network will be discussed, mainly focussing on how environmental cues regulate c-di-GMP signalling, protein-protein interaction mediated functional regulation, heterogeneity of c-di-GMP and cross talk between c-di-GMP signalling and other signalling systems. Understanding the molecular mechanism underlying the complex c-di-GMP signalling network would be beneficial for developing therapeutic approaches and antibacterial agents to combat the threat from P. aeruginosa.
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Affiliation(s)
- Qishun Feng
- School of Medicine, Southern University of Science and Technology, Shenzhen, PR China
| | - Jianuan Zhou
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, PR China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, PR China
| | - Lianhui Zhang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, PR China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, PR China
| | - Yang Fu
- School of Medicine, Southern University of Science and Technology, Shenzhen, PR China
| | - Liang Yang
- School of Medicine, Southern University of Science and Technology, Shenzhen, PR China
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Bottery MJ, Johansen HK, Pitchford JW, Friman VP. Co-occurring microflora and mucin drive Pseudomonas aeruginosa diversification and pathoadaptation. ISME COMMUNICATIONS 2024; 4:ycae043. [PMID: 38707844 PMCID: PMC11067959 DOI: 10.1093/ismeco/ycae043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Revised: 03/25/2024] [Accepted: 03/25/2024] [Indexed: 05/07/2024]
Abstract
While several environmental factors contribute to the evolutionary diversification of the pathogenic bacterium Pseudomonas aeruginosa during cystic fibrosis lung infections, relatively little is known about the impact of the surrounding microbiota. By using in vitro experimental evolution, we show that the presence of Stenotrophomonas maltophilia, Staphylococcus aureus, or them both, prevent the evolution of loss of virulence, which repeatedly occurs in the absence of these species due to mutations in regulators of the Pseudomonas Quinolone Signal quorum sensing system, vqsM and pqsR. Moreover, the strength of the effect of co-occurring species is attenuated through changes in the physical environment by the addition of mucin, resulting in selection for phenotypes resembling those evolved in the absence of the co-occurring species. Together, our findings show that variation in mucosal environment and the surrounding polymicrobial environment can determine the evolutionary trajectory of P. aeruginosa, partly explaining its diversification and pathoadaptation from acute to chronic phenotype during cystic fibrosis lung infections.
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Affiliation(s)
- Michael J Bottery
- Division of Evolution Infection and Genomics, School of Biological Sciences, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Helle Krogh Johansen
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen University Hospital, Copenhagen 9301, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark
| | - Jon W Pitchford
- Department of Biology, University of York, Wentworth Way, York YO10 5DD, United Kingdom
- Department of Mathematics, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Ville-Petri Friman
- Department of Biology, University of York, Wentworth Way, York YO10 5DD, United Kingdom
- Department of Microbiology, University of Helsinki, Helsinki 00014, Finland
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Kotecka K, Kawalek A, Modrzejewska-Balcerek M, Gawor J, Zuchniewicz K, Gromadka R, Bartosik AA. Functional Characterization of TetR-like Transcriptional Regulator PA3973 from Pseudomonas aeruginosa. Int J Mol Sci 2022; 23:ijms232314584. [PMID: 36498910 PMCID: PMC9736018 DOI: 10.3390/ijms232314584] [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: 10/28/2022] [Revised: 11/17/2022] [Accepted: 11/19/2022] [Indexed: 11/24/2022] Open
Abstract
Pseudomonas aeruginosa, a human opportunistic pathogen, is a common cause of nosocomial infections. Its ability to survive under different conditions relies on a complex regulatory network engaging transcriptional regulators controlling metabolic pathways and capabilities to efficiently use the available resources. P. aeruginosa PA3973 encodes an uncharacterized TetR family transcriptional regulator. In this study, we applied a transcriptome profiling (RNA-seq), genome-wide identification of binding sites using ChIP-seq, as well as the phenotype analyses to unravel the biological role of PA3973. Transcriptional profiling of P. aeruginosa PAO1161 overexpressing PA3973 showed changes in the mRNA level of 648 genes. Concomitantly, ChIP-seq analysis identified more than 300 PA3973 binding sites in the P. aeruginosa genome. A 13 bp sequence motif was indicated as the binding site of PA3973. The PA3973 regulon encompasses the PA3972-PA3971 genes encoding a probable acyl-CoA dehydrogenase and a thioesterase. In vitro analysis showed PA3973 binding to PA3973p. Accordingly, the lack of PA3973 triggered increased expression of PA3972 and PA3971. The ∆PA3972-71 PAO1161 strain demonstrated impaired growth in the presence of stress-inducing agents hydroxylamine or hydroxyurea, thus suggesting the role of PA3972-71 in pathogen survival upon stress. Overall our results showed that TetR-type transcriptional regulator PA3973 has multiple binding sites in the P. aeruginosa genome and influences the expression of diverse genes, including PA3972-PA3971, encoding proteins with a proposed role in stress response.
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Hamde F, Dinka H, Naimuddin M. In silico analysis of promoter regions to identify regulatory elements in TetR family transcriptional regulatory genes of Mycobacterium colombiense CECT 3035. J Genet Eng Biotechnol 2022; 20:53. [PMID: 35357597 PMCID: PMC8971250 DOI: 10.1186/s43141-022-00331-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 03/09/2022] [Indexed: 12/18/2022]
Abstract
Background Mycobacterium colombiense is an acid-fast, non-motile, rod-shaped mycobacterium confirmed to cause respiratory disease and disseminated infection in immune-compromised patients, and lymphadenopathy in immune-competent children. It has virulence mechanisms that allow them to adapt, survive, replicate, and produce diseases in the host. To tackle the diseases caused by M. colombiense, understanding of the regulation mechanisms of its genes is important. This paper, therefore, analyzes transcription start sites, promoter regions, motifs, transcription factors, and CpG islands in TetR family transcriptional regulatory (TFTR) genes of M. colombiense CECT 3035 using neural network promoter prediction, MEME, TOMTOM algorithms, and evolutionary analysis with the help of MEGA-X. Results The analysis of 22 protein coding TFTR genes of M. colombiense CECT 3035 showed that 86.36% and 13.64% of the gene sequences had one and two TSSs, respectively. Using MEME, we identified five motifs (MTF1, MTF2, MTF3, MTF4, and MTF5) and MTF1 was revealed as the common promoter motif for 100% TFTR genes of M. colombiense CECT 3035 which may serve as binding site for transcription factors that shared a minimum homology of 95.45%. MTF1 was compared to the registered prokaryotic motifs and found to match with 15 of them. MTF1 serves as the binding site mainly for AraC, LexA, and Bacterial histone-like protein families. Other protein families such as MATP, RR, σ-70 factor, TetR, LytTR, LuxR, and NAP also appear to be the binding candidates for MTF1. These families are known to have functions in virulence mechanisms, metabolism, quorum sensing, cell division, and antibiotic resistance. Furthermore, it was found that TFTR genes of M. colombiense CECT 3035 have many CpG islands with several fragments in their CpG islands. Molecular evolutionary genetic analysis showed close relationship among the genes. Conclusion We believe these findings will provide a better understanding of the regulation of TFTR genes in M. colombiense CECT 3035 involved in vital processes such as cell division, pathogenesis, and drug resistance and are likely to provide insights for drug development important to tackle the diseases caused by this mycobacterium. We believe this is the first report of in silico analyses of the transcriptional regulation of M. colombiense TFTR genes.
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Affiliation(s)
- Feyissa Hamde
- Department of Applied Biology, School of Applied Natural Science, Adama Science and Technology University, P.O. Box 1888, Adama, Ethiopia.
| | - Hunduma Dinka
- Department of Applied Biology, School of Applied Natural Science, Adama Science and Technology University, P.O. Box 1888, Adama, Ethiopia
| | - Mohammed Naimuddin
- Department of Applied Biology, School of Applied Natural Science, Adama Science and Technology University, P.O. Box 1888, Adama, Ethiopia.
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Jia H, Cao S, Wu Y, Zhu W, Luo J, Shen Y, Wang M. Genomewide Transcriptome Responses of Arthrobacter simplex to Cortisone Acetate and its Mutants with Enhanced Δ 1-Dehydrogenation Efficiency. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2021; 69:12773-12784. [PMID: 34694802 DOI: 10.1021/acs.jafc.1c04934] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Due to its superior Δ1-dehydrogenation ability, Arthrobacter simplex has been widely used for the biotransformation of cortisone acetate (CA) into prednisone acetate (PA) in the steroid industry. However, its molecular fundamentals are still unclear. Herein, the genome organization, gene regulation, and previously unreported genes involved in Δ1-dehydrogenation are revealed through genome and transcriptome analysis. A comparative study of transcriptomes of an industrial strain induced by CA or at different biotransformation periods was performed. By overexpression, the roles of six genes in CA conversion were confirmed, among which sufC and hsaA behaved better by reinforcing catalytic enzyme activity and substrate transmembrane transport. Additionally, GroEL endowed cells with the strongest stress tolerance by alleviating oxidative damage and enhancing energy levels. Finally, an optimal strain was created by coexpressing three genes, achieving 46.8 and 70.6% increase in PA amount and productivity compared to the initial values, respectively. Our study expanded the understanding of the Δ1-dehydrogenation mechanism and offered an effective approach for excellent steroid-transforming strains.
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Affiliation(s)
- Hongchen Jia
- Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science &Technology), Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Shuting Cao
- Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science &Technology), Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Yan Wu
- Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science &Technology), Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Wencheng Zhu
- Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science &Technology), Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Jianmei Luo
- Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science &Technology), Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Yanbing Shen
- Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science &Technology), Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Min Wang
- Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science &Technology), Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
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Krell T, Gavira JA, Velando F, Fernández M, Roca A, Monteagudo-Cascales E, Matilla MA. Histamine: A Bacterial Signal Molecule. Int J Mol Sci 2021; 22:6312. [PMID: 34204625 PMCID: PMC8231116 DOI: 10.3390/ijms22126312] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 06/09/2021] [Accepted: 06/10/2021] [Indexed: 02/07/2023] Open
Abstract
Bacteria have evolved sophisticated signaling mechanisms to coordinate interactions with organisms of other domains, such as plants, animals and human hosts. Several important signal molecules have been identified that are synthesized by members of different domains and that play important roles in inter-domain communication. In this article, we review recent data supporting that histamine is a signal molecule that may play an important role in inter-domain and inter-species communication. Histamine is a key signal molecule in humans, with multiple functions, such as being a neurotransmitter or modulator of immune responses. More recent studies have shown that bacteria have evolved different mechanisms to sense histamine or histamine metabolites. Histamine sensing in the human pathogen Pseudomonas aeruginosa was found to trigger chemoattraction to histamine and to regulate the expression of many virulence-related genes. Further studies have shown that many bacteria are able to synthesize and secrete histamine. The release of histamine by bacteria in the human gut was found to modulate the host immune responses and, at higher doses, to result in host pathologies. The elucidation of the role of histamine as an inter-domain signaling molecule is an emerging field of research and future investigation is required to assess its potential general nature.
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Affiliation(s)
- Tino Krell
- Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Prof. Albareda 1, 18008 Granada, Spain; (F.V.); (E.M.-C.)
| | - José A. Gavira
- Laboratory of Crystallographic Studies, IACT (CSIC-UGR), Avenida de las Palmeras 4, 18100 Armilla, Spain;
| | - Félix Velando
- Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Prof. Albareda 1, 18008 Granada, Spain; (F.V.); (E.M.-C.)
| | - Matilde Fernández
- Department of Microbiology, Facultad de Farmacia, Campus Universitario de Cartuja, Universidad de Granada, 18071 Granada, Spain; (M.F.); (A.R.)
| | - Amalia Roca
- Department of Microbiology, Facultad de Farmacia, Campus Universitario de Cartuja, Universidad de Granada, 18071 Granada, Spain; (M.F.); (A.R.)
| | - Elizabet Monteagudo-Cascales
- Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Prof. Albareda 1, 18008 Granada, Spain; (F.V.); (E.M.-C.)
| | - Miguel A. Matilla
- Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Prof. Albareda 1, 18008 Granada, Spain; (F.V.); (E.M.-C.)
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Kotecka K, Kawalek A, Kobylecki K, Bartosik AA. The AraC-Type Transcriptional Regulator GliR (PA3027) Activates Genes of Glycerolipid Metabolism in Pseudomonas aeruginosa. Int J Mol Sci 2021; 22:5066. [PMID: 34064685 PMCID: PMC8151288 DOI: 10.3390/ijms22105066] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 05/04/2021] [Accepted: 05/06/2021] [Indexed: 12/13/2022] Open
Abstract
Pseudomonas aeruginosa encodes a large set of transcriptional regulators (TRs) that modulate and manage cellular metabolism to survive in variable environmental conditions including that of the human body. The AraC family regulators are an abundant group of TRs in bacteria, mostly acting as gene expression activators, controlling diverse cellular functions (e.g., carbon metabolism, stress response, and virulence). The PA3027 protein from P. aeruginosa has been classified in silico as a putative AraC-type TR. Transcriptional profiling of P. aeruginosa PAO1161 overexpressing PA3027 revealed a spectacular increase in the mRNA levels of PA3026-PA3024 (divergent to PA3027), PA3464, and PA3342 genes encoding proteins potentially involved in glycerolipid metabolism. Concomitantly, chromatin immunoprecipitation-sequencing (ChIP-seq) analysis revealed that at least 22 regions are bound by PA3027 in the PAO1161 genome. These encompass promoter regions of PA3026, PA3464, and PA3342, showing the major increase in expression in response to PA3027 excess. In Vitro DNA binding assay confirmed interactions of PA3027 with these regions. Furthermore, promoter-reporter assays in a heterologous host showed the PA3027-dependent activation of the promoter of the PA3026-PA3024 operon. Two motifs representing the preferred binding sites for PA3027, one localized upstream and one overlapping with the -35 promoter sequence, were identified in PA3026p and our data indicate that both motifs are required for full activation of this promoter by PA3027. Overall, the presented data show that PA3027 acts as a transcriptional regulator in P. aeruginosa, activating genes likely engaged in glycerolipid metabolism. The GliR name, from a glycerolipid metabolism regulator, is proposed for PA3027 of P. aeruginosa.
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Affiliation(s)
| | | | | | - Aneta Agnieszka Bartosik
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland; (K.K.); (A.K.); (K.K.)
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Lippa AM, Gebhardt MJ, Dove SL. H-NS-like proteins in Pseudomonas aeruginosa coordinately silence intragenic transcription. Mol Microbiol 2020; 115:1138-1151. [PMID: 33245158 DOI: 10.1111/mmi.14656] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2020] [Revised: 11/22/2020] [Accepted: 11/23/2020] [Indexed: 01/22/2023]
Abstract
The H-NS-like proteins MvaT and MvaU act coordinately as global repressors in Pseudomonas aeruginosa by binding to AT-rich regions of the chromosome. Although cells can tolerate loss of either protein, identifying their combined regulatory effects has been challenging because the loss of both proteins is lethal due to induction of prophage Pf4 and subsequent superinfection of the cell. In other bacteria, H-NS promotes the cellular fitness by inhibiting intragenic transcription from AT-rich target regions, preventing them from sequestering RNA polymerase; however, it is not known whether MvaT and MvaU function similarly. Here, we utilize a parental strain that cannot be infected by Pf4 phage to define the collective MvaT and MvaU regulon and demonstrate that the combined loss of both MvaT and MvaU leads to increased intragenic transcription from loci directly controlled by these proteins. We further show that the loss of MvaT and MvaU leads to a striking redistribution of RNA polymerase containing σ70 to genomic regions vacated by these proteins. Our findings suggest that the ability of H-NS-like proteins to repress intragenic transcription is a universal function of these proteins and point to a second mechanism by which MvaT and MvaU may contribute to the growth of P. aeruginosa.
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Affiliation(s)
- Andrew M Lippa
- Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Michael J Gebhardt
- Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Simon L Dove
- Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
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Beasley KL, Cristy SA, Elmassry MM, Dzvova N, Colmer-Hamood JA, Hamood AN. During bacteremia, Pseudomonas aeruginosa PAO1 adapts by altering the expression of numerous virulence genes including those involved in quorum sensing. PLoS One 2020; 15:e0240351. [PMID: 33057423 PMCID: PMC7561203 DOI: 10.1371/journal.pone.0240351] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 09/24/2020] [Indexed: 12/17/2022] Open
Abstract
Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that produces numerous virulence factors and causes serious infections in trauma patients and patients with severe burns. We previously showed that the growth of P. aeruginosa in blood from severely burned or trauma patients altered the expression of numerous genes. However, the specific influence of whole blood from healthy volunteers on P. aeruginosa gene expression is not known. Transcriptome analysis of P. aeruginosa grown for 4 h in blood from healthy volunteers compared to that when grown in laboratory medium revealed that the expression of 1085 genes was significantly altered. Quorum sensing (QS), QS-related, and pyochelin synthesis genes were downregulated, while genes of the type III secretion system and those for pyoverdine synthesis were upregulated. The observed effect on the QS and QS-related genes was shown to reside within serum fraction: growth of PAO1 in the presence of 10% human serum from healthy volunteers significantly reduced the expression of QS and QS-regulated genes at 2 and 4 h of growth but significantly enhanced their expression at 8 h. Additionally, the production of QS-regulated virulence factors, including LasA and pyocyanin, was also influenced by the presence of human serum. Serum fractionation experiments revealed that part of the observed effect resides within the serum fraction containing <10-kDa proteins. Growth in serum reduced the production of many PAO1 outer membrane proteins but enhanced the production of others including OprF, a protein previously shown to play a role in the regulation of QS gene expression. These results suggest that factor(s) within human serum: 1) impact P. aeruginosa pathogenesis by influencing the expression of different genes; 2) differentially regulate the expression of QS and QS-related genes in a growth phase- or time-dependent mechanism; and 3) manipulate the production of P. aeruginosa outer membrane proteins.
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Affiliation(s)
- Kellsie L. Beasley
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, Texas, Untied States of America
| | - Shane A. Cristy
- Honors College, Texas Tech University, Lubbock, Texas, Untied States of America
| | - Moamen M. Elmassry
- Department of Biological Sciences, Texas Tech University, Lubbock, Texas, Untied States of America
| | - Nyaradzo Dzvova
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, Texas, Untied States of America
| | - Jane A. Colmer-Hamood
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, Texas, Untied States of America
- Department of Medical Education, Texas Tech University Health Sciences Center, Lubbock, Texas, Untied States of America
| | - Abdul N. Hamood
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, Texas, Untied States of America
- Department of Surgery, Texas Tech University Health Sciences Center, Lubbock, Texas, Untied States of America
- * E-mail:
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Shao X, Xie Y, Zhang Y, Liu J, Ding Y, Wu M, Wang X, Deng X. Novel therapeutic strategies for treating Pseudomonas aeruginosa infection. Expert Opin Drug Discov 2020; 15:1403-1423. [PMID: 32880507 DOI: 10.1080/17460441.2020.1803274] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
INTRODUCTION Persistent infections caused by the superbug Pseudomonas aeruginosa and its resistance to multiple antimicrobial agents are huge threats to patients with cystic fibrosis as well as those with compromised immune systems. Multidrug-resistant P. aeruginosa has posed a major challenge to conventional antibiotics and therapeutic approaches, which show limited efficacy and cause serious side effects. The public demand for new antibiotics is enormous; yet, drug development pipelines have started to run dry with limited targets available for inventing new antibacterial drugs. Consequently, it is important to uncover potential therapeutic targets. AREAS COVERED The authors review the current state of drug development strategies that are promising in terms of the development of novel and potent drugs to treat P. aeruginosa infection. EXPERT OPINION The prevention of P. aeruginosa infection is increasingly challenging. Furthermore, targeting key virulence regulators has great potential for developing novel anti-P. aeruginosa drugs. Additional promising strategies include bacteriophage therapy, immunotherapies, and antimicrobial peptides. Additionally, the authors believe that in the coming years, the overall network of molecular regulatory mechanism of P. aeruginosa virulence will be fully elucidated, which will provide more novel and promising drug targets for treating P. aeruginosa infections.
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Affiliation(s)
- Xiaolong Shao
- Department of Biomedical Sciences, City University of Hong Kong , Hong Kong SAR, China
| | - Yingpeng Xie
- Department of Biomedical Sciences, City University of Hong Kong , Hong Kong SAR, China
| | - Yingchao Zhang
- Department of Biomedical Sciences, City University of Hong Kong , Hong Kong SAR, China
| | - Jingui Liu
- Department of Biomedical Sciences, City University of Hong Kong , Hong Kong SAR, China
| | - Yiqing Ding
- Department of Biomedical Sciences, City University of Hong Kong , Hong Kong SAR, China
| | - Min Wu
- Department of Biomedical Sciences, University of North Dakota , Grand Forks, North Dakota, USA
| | - Xin Wang
- Department of Biomedical Sciences, City University of Hong Kong , Hong Kong SAR, China
| | - Xin Deng
- Department of Biomedical Sciences, City University of Hong Kong , Hong Kong SAR, China.,Shenzhen Research Institute, City University of Hong Kong , Shenzhen, China
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12
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Abstract
It is not fully understood how phosphate deficiency could influence the virulence of Pseudomonas aeruginosa through modulation of the bacterial QS systems. This report presents a systemic investigation on the impact of phosphate depletion on the hierarchy of quorum sensing systems of P. aeruginosa. The results showed that phosphate stress could have an extensive impact on the QS networks of this bacterial pathogen. Among the 7 QS regulatory genes representing the 3 sets of QS systems tested, 4 were significantly upregulated by phosphate depletion stress through the PhoR/PhoB two-component regulatory system, especially the upstream QS regulatory gene lasI. We also present evidence that the response regulator PhoB was a strong competitor against the las regulators LasR and RsaL for the lasI promoter, unveiling the mechanistic basis of the process by which phosphate stress could modulate the bacterial QS systems. The hierarchical quorum sensing (QS) systems of Pseudomonas aeruginosa, consisting of las, pqs, and rhl, coordinate the expression of bacterial virulence genes. Previous studies showed that under phosphate deficiency conditions, two-component regulatory system PhoRB could activate various genes involved in cytotoxicity through modulation of QS systems, but the mechanism by which PhoR/PhoB influences QS remains largely unknown. Here, we provide evidence that among the key QS regulatory genes in P. aeruginosa, rhlR, pqsA, mvfR, and lasI were activated by the response regulator PhoB under phosphate-depleted conditions. We show that PhoB is a strong competitor against LasR and RsaL for binding to the promoter of lasI and induces significant expression of lasI, rhlR, and mvfR. However, expression of lasI, encoding the signal 3-oxo-C12-HSL, was increased only marginally under the same phosphate-depleted conditions. This seeming inconsistency was attributed to the induction of pvdQ, which encodes an enzyme for degradation of 3-oxo-C12-HSL signal molecules. Taken together, the results from this study demonstrate that through the two-component regulatory system PhoR/PhoB, phosphate depletion stress could influence the QS network by modulating several key regulators, including lasI, rhlR, mvfR, and pvdQ. The findings highlight not only the potency of the PhoR/PhoB-mediated bacterial stress response mechanism but also the plasticity of the P. aeruginosa QS systems in coping with the changed environmental conditions. IMPORTANCE It is not fully understood how phosphate deficiency could influence the virulence of Pseudomonas aeruginosa through modulation of the bacterial QS systems. This report presents a systemic investigation on the impact of phosphate depletion on the hierarchy of quorum sensing systems of P. aeruginosa. The results showed that phosphate stress could have an extensive impact on the QS networks of this bacterial pathogen. Among the 7 QS regulatory genes representing the 3 sets of QS systems tested, 4 were significantly upregulated by phosphate depletion stress through the PhoR/PhoB two-component regulatory system, especially the upstream QS regulatory gene lasI. We also present evidence that the response regulator PhoB was a strong competitor against the las regulators LasR and RsaL for the lasI promoter, unveiling the mechanistic basis of the process by which phosphate stress could modulate the bacterial QS systems.
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Mesquita CS, Soares-Castro P, Faustino A, Santos HM, Capelo JL, Santos P. Identification of genomic loci associated with genotypic and phenotypic variation among Pseudomonas aeruginosa clinical isolates from pneumonia. Microb Pathog 2019; 136:103702. [PMID: 31472259 DOI: 10.1016/j.micpath.2019.103702] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 08/27/2019] [Accepted: 08/28/2019] [Indexed: 11/19/2022]
Abstract
In this work, a genotype-phenotype survey of a highly diversified Pseudomonas aeruginosa collection was conducted, aiming to detail pathogen-associated scenarios that clinicians face nowadays. Genetic relation based on RAPD-PCR of 705 isolates, retrieved from 424 patients and several clinical contexts, reported an almost isolate-specific molecular-pattern. Pneumonia-associated isolates HB13 and HB15, clustered in the same RAPD-PCR group, were selected to evaluate the genomic background underlying their contrasting antibiotic resistance and virulence. The HB13 genome harbors antibiotic-inactivating enzymes-coding genes (e.g. aac(3)-Ia, arr, blaVIM-2) and single-nucleotide variations (SNVs) in antibiotic targets, likely accounting for its pan-resistance, whereas HB15 susceptibility correlated to predicted dysfunctional alleles. Isolate HB13 showed the unprecedented rhl-cluster absence and variations in other pathogen competitiveness contributors. Conversely, HB15 genome comprises exoenzyme-coding genes and SNVs linked to increased virulence. Secretome analysis identified signatures features with unknown function as potential novel pathogenic (e.g. a MATE-protein in HB13, a protease in HB15) and antibiotic resistance (a HlyD-like secretion protein in HB13) determinants. Detection of active prophages, proteases (including protease IV and alkaline metalloproteinase), a porin and a peptidase in HB15 highlights the secreted arsenal likely essential for its virulent behavior. The presented phenotype-genome association will contribute to the current knowledge on Pseudomonas aeruginosa pathogenomics.
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Affiliation(s)
- Cristina S Mesquita
- CBMA - Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - Pedro Soares-Castro
- CBMA - Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - Alberta Faustino
- Clinical Pathology Service, Hospital de Braga, 4710-243, Braga, Portugal
| | - Hugo M Santos
- UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal; PROTEOMASS Scientific Society, Madan Park, Rua dos Inventores, 2825-152, Caparica, Portugal
| | - José L Capelo
- UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal; PROTEOMASS Scientific Society, Madan Park, Rua dos Inventores, 2825-152, Caparica, Portugal
| | - Pedro Santos
- CBMA - Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal.
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Otero-Asman JR, Wettstadt S, Bernal P, Llamas MA. Diversity of extracytoplasmic function sigma (σ ECF ) factor-dependent signaling in Pseudomonas. Mol Microbiol 2019; 112:356-373. [PMID: 31206859 DOI: 10.1111/mmi.14331] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/10/2019] [Indexed: 12/23/2022]
Abstract
Pseudomonas bacteria are widespread and are found in soil and water, as well as pathogens of both plants and animals. The ability of Pseudomonas to colonize many different environments is facilitated by the multiple signaling systems these bacteria contain that allow Pseudomonas to adapt to changing circumstances by generating specific responses. Among others, signaling through extracytoplasmic function σ (σECF ) factors is extensively present in Pseudomonas. σECF factors trigger expression of functions required under particular conditions in response to specific signals. This manuscript reviews the phylogeny and biological roles of σECF factors in Pseudomonas, and highlights the diversity of σECF -signaling pathways of this genus in terms of function and activation. We show that Pseudomonas σECF factors belong to 16 different phylogenetic groups. Most of them are included within the iron starvation group and are mainly involved in iron acquisition. The second most abundant group is formed by RpoE-like σECF factors, which regulate the responses to cell envelope stress. Other groups controlling solvent tolerance, biofilm formation and the response to oxidative stress, among other functions, are present in lower frequency. The role of σECF factors in the virulence of Pseudomonas pathogenic species is described.
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Affiliation(s)
- Joaquín R Otero-Asman
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Sarah Wettstadt
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Patricia Bernal
- Department of Biology, Faculty of Sciences, Universidad Autónoma de Madrid, Madrid, Spain
| | - María A Llamas
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
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15
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An integrated genomic regulatory network of virulence-related transcriptional factors in Pseudomonas aeruginosa. Nat Commun 2019; 10:2931. [PMID: 31270321 PMCID: PMC6610081 DOI: 10.1038/s41467-019-10778-w] [Citation(s) in RCA: 91] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Accepted: 05/30/2019] [Indexed: 01/12/2023] Open
Abstract
The virulence of Pseudomonas aeruginosa, a Gram-negative opportunistic pathogen, is regulated by many transcriptional factors (TFs) that control the expression of quorum sensing and protein secretion systems. Here, we report a genome-wide, network-based approach to dissect the crosstalk between 20 key virulence-related TFs. Using chromatin immunoprecipitation coupled with high-throughput sequencing (ChIP-seq), as well as RNA-seq, we identify 1200 TF-bound genes and 4775 differentially expressed genes. We experimentally validate 347 of these genes as functional target genes, and describe the regulatory relationships of the 20 TFs with their targets in a network that we call ‘Pseudomonas aeruginosa genomic regulatory network’ (PAGnet). Analysis of the network led to the identification of novel functions for two TFs (ExsA and GacA) in quorum sensing and nitrogen metabolism. Furthermore, we present an online platform and R package based on PAGnet to facilitate updating and user-customised analyses. The virulence of Pseudomonas aeruginosa is regulated by many transcriptional factors (TFs). Here, the authors study the crosstalk between 20 key virulence-related TFs, validate 347 functional target genes, and describe the regulatory relationships of the 20 TFs with their targets in a network that is available as an online platform.
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16
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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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Abstract
Antibiotics have saved millions of lives over the past decades. However, the accumulation of so many antibiotic resistance genes by some clinically relevant pathogens has begun to lead to untreatable infections worldwide. The current antibiotic resistance crisis will require greater efforts by governments and the scientific community to increase the research and development of new antibacterial drugs with new mechanisms of action. A major challenge is the identification of novel microbial targets, essential for in vivo growth or pathogenicity, whose inhibitors can overcome the currently circulating resistome of human pathogens. In this article, we focus on the potential high value of bacterial transcriptional regulators as targets for the development of new antibiotics, discussing in depth the molecular role of these regulatory proteins in bacterial physiology and pathogenesis. Recent advances in the search for novel compounds that inhibit the biological activity of relevant transcriptional regulators in pathogenic bacteria are reviewed.
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18
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Romero-Lastra P, Sánchez MC, Ribeiro-Vidal H, Llama-Palacios A, Figuero E, Herrera D, Sanz M. Comparative gene expression analysis of Porphyromonas gingivalis ATCC 33277 in planktonic and biofilms states. PLoS One 2017; 12:e0174669. [PMID: 28369099 PMCID: PMC5378342 DOI: 10.1371/journal.pone.0174669] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Accepted: 03/13/2017] [Indexed: 11/24/2022] Open
Abstract
Background and objective Porphyromonas gingivalis is a keystone pathogen in the onset and progression of periodontitis. Its pathogenicity has been related to its presence and survival within the subgingival biofilm. The aim of the present study was to compare the genome-wide transcription activities of P. gingivalis in biofilm and in planktonic growth, using microarray technology. Material and methods P. gingivalis ATCC 33277 was incubated in multi-well culture plates at 37°C for 96 hours under anaerobic conditions using an in vitro static model to develop both the planktonic and biofilm states (the latter over sterile ceramic calcium hydroxyapatite discs). The biofilm development was monitored by Confocal Laser Scanning Microscopy (CLSM) and Scanning Electron Microscopy (SEM). After incubation, the bacterial cells were harvested and total RNA was extracted and purified. Three biological replicates for each cell state were independently hybridized for transcriptomic comparisons. A linear model was used for determining differentially expressed genes and reverse transcription quantitative polymerase chain reaction (RT-qPCR) was used to confirm differential expression. The filtering criteria of ≥ ±2 change in gene expression and significance p-values of <0.05 were selected. Results A total of 92 out of 1,909 genes (4.8%) were differentially expressed by P. gingivalis growing in biofilm compared to planktonic. The 54 up-regulated genes in biofilm growth were mainly related to cell envelope, transport, and binding or outer membranes proteins. Thirty-eight showed decreased expression, mainly genes related to transposases or oxidative stress. Conclusion The adaptive response of P. gingivalis in biofilm growth demonstrated a differential gene expression.
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Affiliation(s)
- P. Romero-Lastra
- Laboratory of Dental Research, University Complutense, Madrid, Spain
| | - MC. Sánchez
- Laboratory of Dental Research, University Complutense, Madrid, Spain
| | - H. Ribeiro-Vidal
- Laboratory of Dental Research, University Complutense, Madrid, Spain
| | - A. Llama-Palacios
- Laboratory of Dental Research, University Complutense, Madrid, Spain
| | - E. Figuero
- Laboratory of Dental Research, University Complutense, Madrid, Spain
- ETEP (Etiology and Therapy of Periodontal Diseases) Research Group, University Complutense, Madrid, Spain
| | - D. Herrera
- ETEP (Etiology and Therapy of Periodontal Diseases) Research Group, University Complutense, Madrid, Spain
| | - M. Sanz
- ETEP (Etiology and Therapy of Periodontal Diseases) Research Group, University Complutense, Madrid, Spain
- * E-mail:
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19
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Okino N, Ito M. Molecular mechanism for sphingosine-induced Pseudomonas ceramidase expression through the transcriptional regulator SphR. Sci Rep 2016; 6:38797. [PMID: 27941831 PMCID: PMC5150637 DOI: 10.1038/srep38797] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Accepted: 11/11/2016] [Indexed: 01/08/2023] Open
Abstract
Pseudomonas aeruginosa, an opportunistic, but serious multidrug-resistant pathogen, secretes a ceramidase capable of cleaving the N-acyl linkage of ceramide to generate fatty acids and sphingosine. We previously reported that the secretion of P. aeruginosa ceramidase was induced by host-derived sphingolipids, through which phospholipase C-induced hemolysis was significantly enhanced. We herein investigated the gene(s) regulating sphingolipid-induced ceramidase expression and identified SphR, which encodes a putative AraC family transcriptional regulator. Disruption of the sphR gene in P. aeruginosa markedly decreased the sphingomyelin-induced secretion of ceramidase, reduced hemolytic activity, and resulted in the loss of sphingomyelin-induced ceramidase expression. A microarray analysis confirmed that sphingomyelin significantly induced ceramidase expression in P. aeruginosa. Furthermore, an electrophoretic mobility shift assay revealed that SphR specifically bound free sphingoid bases such as sphingosine, dihydrosphingosine, and phytosphingosine, but not sphingomyelin or ceramide. A β-galactosidase-assisted promoter assay showed that sphingosine activated ceramidase expression through SphR at a concentration of 100 nM. Collectively, these results demonstrated that sphingosine induces the secretion of ceramidase by promoting the mRNA expression of ceramidase through SphR, thereby enhancing hemolytic phospholipase C-induced cytotoxicity. These results facilitate understanding of the physiological role of bacterial ceramidase in host cells.
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Affiliation(s)
- Nozomu Okino
- The Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
| | - Makoto Ito
- The Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
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20
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Kang H, Gan J, Zhao J, Kong W, Zhang J, Zhu M, Li F, Song Y, Qin J, Liang H. Crystal structure of Pseudomonas aeruginosa RsaL bound to promoter DNA reaffirms its role as a global regulator involved in quorum-sensing. Nucleic Acids Res 2016; 45:699-710. [PMID: 27924027 PMCID: PMC5314801 DOI: 10.1093/nar/gkw954] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2016] [Revised: 09/30/2016] [Accepted: 10/11/2016] [Indexed: 11/17/2022] Open
Abstract
Pseudomonas aeruginosa possesses at least three well-defined quorum-sensing (QS) (las, rhl and pqs) systems that control a variety of important functions including virulence. RsaL is a QS repressor that reduces QS signal production and ensures homeostasis by functioning in opposition to LasR. However, its regulatory role in signal homeostasis remains elusive. Here, we conducted a ChIP-seq assay and revealed that RsaL bound to two new targets, the intergenic regions of PA2228/PA2229 and pqsH/cdpR, which are required for PQS synthesis. Deletion of rsaL reduced transcription of pqsH and cdpR, thus decreasing PQS signal production. The ΔrsaL strain exhibited increased pyocyanin production and reduced biofilm formation, which are dependent on CdpR or PqsH activity. In addition, we solved the structure of the RsaL–DNA complex at a 2.4 Å resolution. Although the overall sequence similarity is quite low, RsaL folds into a HTH-like structure, which is conserved among many transcriptional regulators. Complementation results of the rsaL knockout cells with different rsaL mutants further confirmed the critical role of the DNA-binding residues (including Arg20, Gln27, Gln38, Gly35, Ser37 and Ser42) that are essential for DNA binding. Our findings reveal new targets of RsaL and provide insight into the detailed characterization of the RsaL–DNA interaction.
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Affiliation(s)
- Huaping Kang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Science, Northwest University, Xi'an, Shaanxi 710069, China
| | - Jianhua Gan
- Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai 200438, China
| | - Jingru Zhao
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Science, Northwest University, Xi'an, Shaanxi 710069, China
| | - Weina Kong
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Science, Northwest University, Xi'an, Shaanxi 710069, China
| | - Jing Zhang
- Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai 200438, China
| | - Miao Zhu
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Science, Northwest University, Xi'an, Shaanxi 710069, China
| | - Fan Li
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Science, Northwest University, Xi'an, Shaanxi 710069, China
| | - Yaqin Song
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Science, Northwest University, Xi'an, Shaanxi 710069, China
| | - Jin Qin
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Science, Northwest University, Xi'an, Shaanxi 710069, China
| | - 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
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Araujo LVD, Guimarães CR, Marquita RLDS, Santiago VM, de Souza MP, Nitschke M, Freire DMG. Rhamnolipid and surfactin: Anti-adhesion/antibiofilm and antimicrobial effects. Food Control 2016. [DOI: 10.1016/j.foodcont.2015.11.036] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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22
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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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Dingemans J, Ye L, Hildebrand F, Tontodonati F, Craggs M, Bilocq F, De Vos D, Crabbé A, Van Houdt R, Malfroot A, Cornelis P. The deletion of TonB-dependent receptor genes is part of the genome reduction process that occurs during adaptation of Pseudomonas aeruginosa to the cystic fibrosis lung. Pathog Dis 2014; 71:26-38. [PMID: 24659602 DOI: 10.1111/2049-632x.12170] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 03/12/2014] [Accepted: 03/13/2014] [Indexed: 01/02/2023] Open
Abstract
Chronic Pseudomonas aeruginosa infections are the main cause of morbidity among patients with cystic fibrosis (CF) due to persistent lung inflammation caused by interaction between this bacterium and the immune system. Longitudinal studies of clonally related isolates of a dominant CF clone have indicated that genome reduction frequently occurs during adaptation of P. aeruginosa in the CF lung. In this study, we have evaluated the P. aeruginosa population structure of patients attending the Universitair Ziekenhuis Brussel (UZ Brussel) CF reference center using a combination of genotyping methods. Although the UZ Brussel P. aeruginosa CF population is characterized by the absence of a dominant CF clone, some potential interpatient transmissions could be detected. Interestingly, one of these clones showed deletion of the alternative type I ferripyoverdine receptor gene fpvB. Furthermore, we found that several other TonB-dependent receptors are deleted as well. The genome of one potentially transmissible CF clone was sequenced, revealing large deleted regions including all type III secretion system genes and several virulence genes. Remarkably, a large number of deleted genes are shared between the P. aeruginosa CF clone described in this study and isolates belonging to the dominant Copenhagen CF DK2 clone, suggesting parallel evolution.
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Affiliation(s)
- Jozef Dingemans
- Department of Bioengineering Sciences, Research Group Microbiology, Vrije Universiteit Brussel and VIB Structural Biology, Brussels, Belgium; Unit of Microbiology, Expert Group Molecular and Cellular Biology, Institute for Environment, Health and Safety, Belgian Nuclear Research Centre (SCK CEN), Mol, Belgium
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QsrO a novel regulator of quorum-sensing and virulence in Pseudomonas aeruginosa. PLoS One 2014; 9:e87814. [PMID: 24551066 PMCID: PMC3923755 DOI: 10.1371/journal.pone.0087814] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Accepted: 12/31/2013] [Indexed: 12/11/2022] Open
Abstract
In Pseudomonas aeruginosa, the production of many secreted virulence factors is controlled by a quorum-sensing (QS) circuit, constituted of transcriptional activators (LasR, RhlR, PqsR) and their cognate signaling molecules (3-oxo-C12-HSL, C4-HSL, PQS). QS is a cooperative behavior that is beneficial to a population but can be exploited by “QS-cheaters”, individuals which do not respond to the QS-signal, but can use public goods produced by QS-cooperators. In order to identify QS-deficient clones we designed a genetic screening based on a lasB-lacZ fusion. We isolated one clone (PT1617) deficient in QS-dependent gene expression and virulence factor production despite wild type lasR, rhlR and pqsR alleles. Whole genome sequencing of PT1617 revealed a 3,552 bp deletion encompassing ORFs PA2228-PA2229-PA2230 and the pslA gene. However, complementation of PT1617 by plasmid-encoded copies of these ORFs, did not restore QS. Unexpectedly, gene expression levels of ORFs PA2228, PA2227 (vqsM) and PA2222, located adjacent to the deletion, were 10 to 100 fold higher in mutant PT1617 than in PAO1. When expressed from a constitutive promoter on a plasmid, PA2226, alone was found to be sufficient to confer a QS-negative phenotype on PAO1 as well as on PA14. Co-expression of PA2226 and PA2225 in PAO1 further prevented induction of the type III secretion system. In summary, we have identified a novel genetic locus including ORF2226 termed qsrO (QS-repressing ORF), capable of down-regulating all three known QS-systems in P. aeruginosa.
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25
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Nakai T, Deguchi T, Frébort I, Tanizawa K, Okajima T. Identification of genes essential for the biogenesis of quinohemoprotein amine dehydrogenase. Biochemistry 2014; 53:895-907. [PMID: 24437536 DOI: 10.1021/bi401625m] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The structural genes encoding quinohemoprotein amine dehydrogenase (QHNDH) in Gram-negative bacteria constitute a polycistronic operon together with several nearby genes, which are collectively termed "qhp". We previously showed that the qhpD gene, which lies between qhpA and qhpC (encoding the α and γ subunits of QHNDH, respectively), and the qhpE gene, which follows qhpB (encoding the β subunit), both encode enzymes specifically involved in the posttranslational modification of the γ subunit and are hence essential for QHNDH biogenesis in Paracoccus denitrificans [Ono, K., et al. (2006) J. Biol. Chem. 281, 13672-13684; Nakai, T., et al. (2012) J. Biol. Chem. 287, 6530-6538]. Here we further demonstrate that the qhpF gene, which follows qhpE, and the qhpG and qhpR genes, peripherally located in the complementary strand, are also indispensable for QHNDH biogenesis. The qhpF gene encodes an efflux ABC transporter, which probably translocates the γ subunit into the periplasm in a process coupled with hydrolysis of ATP. The qhpG gene encodes a putative FAD-dependent monooxygenase, which is required for the generation of the quinone cofactor in the γ subunit. Finally, the qhpR gene encodes an AraC family transcriptional regulator, which activates expression of the qhp operon in response to the addition of n-butylamine to the culture medium. Database analysis of the qhp genes reveals that they are very widely distributed, not only in many Gram-negative species but also in a few Gram-positive bacteria.
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Affiliation(s)
- Tadashi Nakai
- Department of Structural Molecular Biology, Institute of Scientific and Industrial Research, Osaka University , Ibaraki, Osaka 567-0047, Japan
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Castelhano Santos N, Pereira MO, Lourenço A. Pathogenicity phenomena in three model systems: from network mining to emerging system-level properties. Brief Bioinform 2013; 16:169-82. [PMID: 24106130 DOI: 10.1093/bib/bbt071] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Understanding the interconnections of microbial pathogenicity phenomena, such as biofilm formation, quorum sensing and antimicrobial resistance, is a tremendous open challenge for biomedical research. Progress made by wet-lab researchers and bioinformaticians in understanding the underlying regulatory phenomena has been significant, with converging evidence from multiple high-throughput technologies. Notably, network reconstructions are already of considerable size and quality, tackling both intracellular regulation and signal mediation in microbial infection. Therefore, it stands to reason that in silico investigations would play a more active part in this research. Drug target identification and drug repurposing could take much advantage of the ability to simulate pathogen regulatory systems, host-pathogen interactions and pathogen cross-talking. Here, we review the bioinformatics resources and tools available for the study of the gram-negative bacterium Pseudomonas aeruginosa, the gram-positive bacterium Staphylococcus aureus and the fungal species Candida albicans. The choice of these three microorganisms fits the rationale of the review converging into pathogens of great clinical importance, which thrive in biofilm consortia and manifest growing antimicrobial resistance.
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Lee J, Wu J, Deng Y, Wang J, Wang C, Wang J, Chang C, Dong Y, Williams P, Zhang LH. A cell-cell communication signal integrates quorum sensing and stress response. Nat Chem Biol 2013; 9:339-43. [PMID: 23542643 DOI: 10.1038/nchembio.1225] [Citation(s) in RCA: 275] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Accepted: 02/26/2013] [Indexed: 01/08/2023]
Abstract
Pseudomonas aeruginosa uses a hierarchical quorum sensing (QS) network consisting of las, pqs and rhl regulatory elements to coordinate the expression of bacterial virulence genes. However, clinical isolates frequently contain loss-of-function mutations in the central las system. This motivated us to search for a mechanism that may functionally substitute las. Here we report identification of a new QS signal, IQS. Disruption of IQS biosynthesis paralyzes the pqs and rhl QS systems and attenuates bacterial virulence. Production of IQS is tightly controlled by las under normal culture conditions but is also activated by phosphate limitation, a common stressor that bacteria encounter during infections. Thus, these results have established an integrated QS system that connects the central las system and phosphate-stress response mechanism to the downstream pqs and rhl regulatory systems. Our discovery highlights the complexity of QS signaling systems and extends the gamut of QS and stress-response mechanisms.
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Affiliation(s)
- Jasmine Lee
- Institute of Molecular and Cell Biology, Proteos, Singapore
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Balasubramanian D, Schneper L, Kumari H, Mathee K. A dynamic and intricate regulatory network determines Pseudomonas aeruginosa virulence. Nucleic Acids Res 2012; 41:1-20. [PMID: 23143271 PMCID: PMC3592444 DOI: 10.1093/nar/gks1039] [Citation(s) in RCA: 317] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Pseudomonas aeruginosa is a metabolically versatile bacterium that is found in a wide range of biotic and abiotic habitats. It is a major human opportunistic pathogen causing numerous acute and chronic infections. The critical traits contributing to the pathogenic potential of P. aeruginosa are the production of a myriad of virulence factors, formation of biofilms and antibiotic resistance. Expression of these traits is under stringent regulation, and it responds to largely unidentified environmental signals. This review is focused on providing a global picture of virulence gene regulation in P. aeruginosa. In addition to key regulatory pathways that control the transition from acute to chronic infection phenotypes, some regulators have been identified that modulate multiple virulence mechanisms. Despite of a propensity for chaotic behaviour, no chaotic motifs were readily observed in the P. aeruginosa virulence regulatory network. Having a ‘birds-eye’ view of the regulatory cascades provides the forum opportunities to pose questions, formulate hypotheses and evaluate theories in elucidating P. aeruginosa pathogenesis. Understanding the mechanisms involved in making P. aeruginosa a successful pathogen is essential in helping devise control strategies.
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Affiliation(s)
- Deepak Balasubramanian
- Department of Biological Sciences, College of Arts and Science, Florida International University, Miami, FL 33199, USA
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Rutherford ST, Bassler BL. Bacterial quorum sensing: its role in virulence and possibilities for its control. Cold Spring Harb Perspect Med 2012; 2:2/11/a012427. [PMID: 23125205 DOI: 10.1101/cshperspect.a012427] [Citation(s) in RCA: 1115] [Impact Index Per Article: 92.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Quorum sensing is a process of cell-cell communication that allows bacteria to share information about cell density and adjust gene expression accordingly. This process enables bacteria to express energetically expensive processes as a collective only when the impact of those processes on the environment or on a host will be maximized. Among the many traits controlled by quorum sensing is the expression of virulence factors by pathogenic bacteria. Here we review the quorum-sensing circuits of Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, and Vibrio cholerae. We outline these canonical quorum-sensing mechanisms and how each uniquely controls virulence factor production. Additionally, we examine recent efforts to inhibit quorum sensing in these pathogens with the goal of designing novel antimicrobial therapeutics.
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Affiliation(s)
- Steven T Rutherford
- Department of Molecular Biology, Princeton University, New Jersey 08544, USA
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The Pseudomonas aeruginosa global regulator VqsR directly inhibits QscR to control quorum-sensing and virulence gene expression. J Bacteriol 2012; 194:3098-108. [PMID: 22505688 DOI: 10.1128/jb.06679-11] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The opportunistic pathogen Pseudomonas aeruginosa has at least three quorum-sensing (QS) systems, including the acyl-homoserine lactone (acyl-HSL)-mediated las and rhl systems, as well as the 2-alkyl-4(1H)-quinolone (AHQ) signal-based system. A group of key regulators of these QS systems have been identified, such as qteE, vqsM, vqsR, and vfr. However, the underlying regulatory mechanisms of these QS systems are not yet fully understood. Here, using electrophoretic mobility shift assays, we demonstrated that VqsR indirectly regulates acyl-HSL systems but specifically binds to the qscR promoter region, which indicates that VqsR influences QS-controlled pathways through QscR. Through a dye-based DNase I footprint assay, we showed that VqsR interacts with an inverted repeat (IR) motif (TCGCCN(8)GGCGA, where N is any nucleotide) in the promoter region of qscR. A genome-wide search identified 50 other promoter regions carrying the same putative IR motif. The recombinant VqsR protein exists as a homodimer in solution. In addition, using a qscR-lux reporter assay and Northern blot hybridization, we found that the transcription level of qscR increased 4-fold in the vqsR deletion strain compared to the wild-type PAO1 strain, indicating vqsR as a negative regulator of qscR. Taken together, these findings provide new insights into the complex regulation network of QS systems in P. aeruginosa.
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Abstract
Many bacteria use 'quorum sensing' (QS) as a mechanism to regulate gene induction in a population-dependent manner. In its simplest sense this involves the accumulation of a signaling metabolite during growth; the binding of this metabolite to a regulator or multiple regulators activates induction or repression of gene expression. However QS regulation is seldom this simple, because other inputs are usually involved. In this review we have focussed on how those other inputs influence QS regulation and as implied by the title, this often occurs by environmental or physiological effects regulating the expression or activity of the QS regulators. The rationale of this review is to briefly introduce the main QS signals used in Gram-negative bacteria and then introduce one of the earliest understood mechanisms of regulation of the regulator, namely the plant-mediated control of expression of the TraR QS regulator in Agrobacterium tumefaciens. We then describe how in several species, multiple QS regulatory systems can act as integrated hierarchical regulatory networks and usually this involves the regulation of QS regulators. Such networks can be influenced by many different physiological and environmental inputs and we describe diverse examples of these. In the final section, we describe different examples of how eukaryotes can influence QS regulation in Gram-negative bacteria.
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Affiliation(s)
- Marijke Frederix
- Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
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Blier AS, Veron W, Bazire A, Gerault E, Taupin L, Vieillard J, Rehel K, Dufour A, Le Derf F, Orange N, Hulen C, Feuilloley MGJ, Lesouhaitier O. C-type natriuretic peptide modulates quorum sensing molecule and toxin production in Pseudomonas aeruginosa. MICROBIOLOGY (READING, ENGLAND) 2011; 157:1929-1944. [PMID: 21511763 PMCID: PMC3755537 DOI: 10.1099/mic.0.046755-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 04/14/2011] [Accepted: 04/18/2011] [Indexed: 12/27/2022]
Abstract
Pseudomonas aeruginosa coordinates its virulence expression and establishment in the host in response to modification of its environment. During the infectious process, bacteria are exposed to and can detect eukaryotic products including hormones. It has been shown that P. aeruginosa is sensitive to natriuretic peptides, a family of eukaryotic hormones, through a cyclic nucleotide-dependent sensor system that modulates its cytotoxicity. We observed that pre-treatment of P. aeruginosa PAO1 with C-type natriuretic peptide (CNP) increases the capacity of the bacteria to kill Caenorhabditis elegans through diffusive toxin production. In contrast, brain natriuretic peptide (BNP) did not affect the capacity of the bacteria to kill C. elegans. The bacterial production of hydrogen cyanide (HCN) was enhanced by both BNP and CNP whereas the production of phenazine pyocyanin was strongly inhibited by CNP. The amount of 2-heptyl-4-quinolone (HHQ), a precursor to 2-heptyl-3-hydroxyl-4-quinolone (Pseudomonas quinolone signal; PQS), decreased after CNP treatment. The quantity of 2-nonyl-4-quinolone (HNQ), another quinolone which is synthesized from HHQ, was also reduced after CNP treatment. Conversely, both BNP and CNP significantly enhanced bacterial production of acylhomoserine lactone (AHL) [e.g. 3-oxo-dodecanoyl-homoserine lactone (3OC12-HSL) and butanoylhomoserine lactone (C4-HSL)]. These results correlate with an induction of lasI transcription 1 h after bacterial exposure to BNP or CNP. Concurrently, pre-treatment of P. aeruginosa PAO1 with either BNP or CNP enhanced PAO1 exotoxin A production, via a higher toxA mRNA level. At the same time, CNP led to elevated amounts of algC mRNA, indicating that algC is involved in C. elegans killing. Finally, we observed that in PAO1, Vfr protein is essential to the pro-virulent effect of CNP whereas the regulator PtxR supports only a part of the CNP pro-virulent activity. Taken together, these data reinforce the hypothesis that during infection natriuretic peptides, particularly CNP, could enhance the virulence of PAO1. This activity is relayed by Vfr and PtxR activation, and a general diagram of the virulence activation cascade involving AHL, HCN and exotoxin A is proposed.
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Affiliation(s)
- Anne-Sophie Blier
- Laboratory of Cold Microbiology – Signals and Micro-environment EA 4312, University of Rouen, 55 Rue Saint Germain, 27000 Evreux, France
| | - Wilfried Veron
- Laboratory of Cold Microbiology – Signals and Micro-environment EA 4312, University of Rouen, 55 Rue Saint Germain, 27000 Evreux, France
| | - Alexis Bazire
- Laboratoire de Biotechnologie et Chimie Marines, Université de Bretagne-Sud B.P. 92116, 56321 Lorient Cedex, France
| | - Eloïse Gerault
- Laboratory of Cold Microbiology – Signals and Micro-environment EA 4312, University of Rouen, 55 Rue Saint Germain, 27000 Evreux, France
| | - Laure Taupin
- Laboratoire de Biotechnologie et Chimie Marines, Université de Bretagne-Sud B.P. 92116, 56321 Lorient Cedex, France
| | | | - Karine Rehel
- Laboratoire de Biotechnologie et Chimie Marines, Université de Bretagne-Sud B.P. 92116, 56321 Lorient Cedex, France
| | - Alain Dufour
- Laboratoire de Biotechnologie et Chimie Marines, Université de Bretagne-Sud B.P. 92116, 56321 Lorient Cedex, France
| | - Franck Le Derf
- SIMA, UMR 6014 COBRA, University of Rouen, 27000 Evreux, France
| | - Nicole Orange
- Laboratory of Cold Microbiology – Signals and Micro-environment EA 4312, University of Rouen, 55 Rue Saint Germain, 27000 Evreux, France
| | - Christian Hulen
- Laboratory of Cold Microbiology – Signals and Micro-environment EA 4312, University of Rouen, 55 Rue Saint Germain, 27000 Evreux, France
| | - Marc G. J. Feuilloley
- Laboratory of Cold Microbiology – Signals and Micro-environment EA 4312, University of Rouen, 55 Rue Saint Germain, 27000 Evreux, France
| | - Olivier Lesouhaitier
- Laboratory of Cold Microbiology – Signals and Micro-environment EA 4312, University of Rouen, 55 Rue Saint Germain, 27000 Evreux, France
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Reis RS, Pereira AG, Neves BC, Freire DMG. Gene regulation of rhamnolipid production in Pseudomonas aeruginosa--a review. BIORESOURCE TECHNOLOGY 2011; 102:6377-84. [PMID: 21498076 DOI: 10.1016/j.biortech.2011.03.074] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Revised: 03/22/2011] [Accepted: 03/23/2011] [Indexed: 05/09/2023]
Abstract
Pseudomonas aeruginosa produces abundant levels of rhamnolipid biosurfactants which exhibit remarkable chemical and physical characteristics, making these compounds attractive targets for biotechnology research. The complex gene regulation network involved in rhamnolipids' biosynthesis represents a challenge to industrial production, which has been the object of a growing number of studies. This article provides a comprehensive review of the known gene regulatory factors involved in rhamnolipid production within P. aeruginosa. The regulatory factors include quorum sensing systems proteins and environmental response, and global regulatory systems within basal bacterial physiology, acting either at transcriptional or post-transcriptional level. The multilayer gene regulation responds to a wide variety of environmental and physiologic signals, and is capable of combining different signals in unique and specific responses.
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Affiliation(s)
- Rodrigo S Reis
- University of Sydney, School of Molecular Biology, NSW 2006, Australia.
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Abdel-Mawgoud AM, Hausmann R, Lépine F, Müller MM, Déziel E. Rhamnolipids: Detection, Analysis, Biosynthesis, Genetic Regulation, and Bioengineering of Production. MICROBIOLOGY MONOGRAPHS 2011. [DOI: 10.1007/978-3-642-14490-5_2] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Liang H, Duan J, Sibley CD, Surette MG, Duan K. Identification of mutants with altered phenazine production in Pseudomonas aeruginosa. J Med Microbiol 2010; 60:22-34. [PMID: 20705730 DOI: 10.1099/jmm.0.022350-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic human pathogen that causes serious and chronic infections. Many secondary metabolites are secreted throughout its growth, among which phenazine is a known virulence factor and signalling molecule. Phenazine is coordinately controlled by the global regulatory quorum-sensing (QS) systems. Despite the detailed understanding of phenazine biosynthesis pathways in P. aeruginosa, the regulatory networks are still not fully clear. In the present study, the regulation of the phzA1B1C1D1E1F1G1 operon (phzA1) has been investigated. Screening of 5000 transposon mutants revealed 14 interrupted genes with altered phzA1 expression, including PA2593 (QteE), which has been identified as a novel regulator of the QS system. Overexpression of qteE in P. aeruginosa significantly reduced the accumulation of homoserine lactone signals and affected the QS-controlled phenotypes such as the production of pyocyanin, rhamnolipids and LasA protease and swarming motility. Indeed, overexpression of qteE in P. aeruginosa attenuated its pathogenicity in the potato and fruit fly infection models. These findings suggest that qteE plays an important role in P. aeruginosa pathogenicity and is part of the regulatory networks controlling phenazine production.
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Affiliation(s)
- Haihua Liang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, Faculty of Life Sciences, Northwest University, Xi'an, Shaanxi 710069, PR China
| | - Jiali Duan
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, Faculty of Life Sciences, Northwest University, Xi'an, Shaanxi 710069, PR China
| | - Christopher D Sibley
- Department of Microbiology and Infectious Diseases, Faculty of Medicine, University of Calgary, 3330 Hospital Drive, Calgary, AB T2N 4N1, Canada
| | - Michael G Surette
- Department of Microbiology and Infectious Diseases, Faculty of Medicine, University of Calgary, 3330 Hospital Drive, Calgary, AB T2N 4N1, Canada
| | - Kangmin Duan
- Department of Microbiology and Infectious Diseases, Faculty of Medicine, University of Calgary, 3330 Hospital Drive, Calgary, AB T2N 4N1, Canada.,Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, Faculty of Life Sciences, Northwest University, Xi'an, Shaanxi 710069, PR China
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Roy PH, Tetu SG, Larouche A, Elbourne L, Tremblay S, Ren Q, Dodson R, Harkins D, Shay R, Watkins K, Mahamoud Y, Paulsen IT. Complete genome sequence of the multiresistant taxonomic outlier Pseudomonas aeruginosa PA7. PLoS One 2010; 5:e8842. [PMID: 20107499 PMCID: PMC2809737 DOI: 10.1371/journal.pone.0008842] [Citation(s) in RCA: 196] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2009] [Accepted: 12/28/2009] [Indexed: 01/26/2023] Open
Abstract
Pseudomonas aeruginosa PA7 is a non-respiratory human isolate from Argentina that is multiresistant to antibiotics. We first sequenced gyrA, gyrB, parC, parE, ampC, ampR, and several housekeeping genes and found that PA7 is a taxonomic outlier. We report here the complete sequence of the 6,588,339 bp genome, which has only about 95% overall identity to other strains. PA7 has multiple novel genomic islands and a total of 51 occupied regions of genomic plasticity. These islands include antibiotic resistance genes, parts of transposons, prophages, and a pKLC102-related island. Several PA7 genes not present in PAO1 or PA14 are putative orthologues of other Pseudomonas spp. and Ralstonia spp. genes. PA7 appears to be closely related to the known taxonomic outlier DSM1128 (ATCC9027). PA7 lacks several virulence factors, notably the entire TTSS region corresponding to PA1690-PA1725 of PAO1. It has neither exoS nor exoU and lacks toxA, exoT, and exoY. PA7 is serotype O12 and pyoverdin type II. Preliminary proteomic studies indicate numerous differences with PAO1, some of which are probably a consequence of a frameshift mutation in the mvfR quorum sensing regulatory gene.
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Affiliation(s)
- Paul H. Roy
- Département de biochimie et de microbiologie, and Centre de recherche en infectiologie, Université Laval, Québec, Québec, Canada
| | - Sasha G. Tetu
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - André Larouche
- Département de biochimie et de microbiologie, and Centre de recherche en infectiologie, Université Laval, Québec, Québec, Canada
| | - Liam Elbourne
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Simon Tremblay
- Département de biochimie et de microbiologie, and Centre de recherche en infectiologie, Université Laval, Québec, Québec, Canada
| | - Qinghu Ren
- J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Robert Dodson
- J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Derek Harkins
- J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Ryan Shay
- J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Kisha Watkins
- J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Yasmin Mahamoud
- J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Ian T. Paulsen
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, New South Wales, Australia
- J. Craig Venter Institute, Rockville, Maryland, United States of America
- * E-mail:
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Abstract
Microorganisms can form tightly knit communities such as biofilms. Many others include marine snow, anaerobic digester granules, the ginger beer plant and bacterial colonies. This chapter is devoted to a survey of the main properties of these communities, with an emphasis on biofilms. We start with attachment to surfaces and the nature of adhesion. The growing community then forms within a matrix, generally of organic macromolecules. Inevitably the environment within such a matrix is different from that outside. Organisms respond by forming crowd-detection and response units; these quorum sensing systems act as switches between planktonic life and the dramatically altered conditions found inside microbial aggregates. The community then matures and changes and may even fail and disappear. Antimicrobial resistance is discussed as an example of multicellular behavior. The multicellular lifestyle has been modeled mathematically and responded to powerful molecular biological techniques. Latterly, microbial systems have been used as models for fundamental evolutionary processes, mostly because of their high rates of reproduction and the ease of genetic manipulation. The life of most microbes is a duality between the yin of the community and the yang of planktonic existence. Sadly far less research has been devoted to adaptation to free-living forms than in the opposite direction.
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Affiliation(s)
- Julian Wimpenny
- Cardiff School of Biosciences, Cardiff University, Cathays Park, Cardiff, Wales
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CbpA: a polarly localized novel cyclic AMP-binding protein in Pseudomonas aeruginosa. J Bacteriol 2009; 191:7193-205. [PMID: 19801409 DOI: 10.1128/jb.00970-09] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Pseudomonas aeruginosa, cyclic AMP (cAMP) signaling regulates the transcription of hundreds of genes encoding diverse virulence factors, including the type II secretion system (T2SS) and type III secretion system (T3SS) and their associated toxins, type IV pili (TFP), and flagella. Vfr, a cAMP-dependent transcriptional regulator that is homologous to the Escherichia coli catabolite repressor protein, is thought to be the major cAMP-binding protein that regulates these important virulence determinants. Using a bioinformatic approach, we have identified a gene (PA4704) encoding an additional putative cAMP-binding protein in P. aeruginosa PAO1, which we herein refer to as CbpA, for cAMP-binding protein A. Structural modeling predicts that CbpA is composed of a C-terminal cAMP-binding (CAP) domain and an N-terminal degenerate CAP domain and is structurally similar to eukaryotic protein kinase A regulatory subunits. We show that CbpA binds to cAMP-conjugated agarose via its C-terminal CAP domain. Using in vitro trypsin protection assays, we demonstrate that CbpA undergoes a conformational change upon cAMP binding. Reporter gene assays and electrophoresis mobility shift assays defined the cbpA promoter and a Vfr-binding site that are necessary for Vfr-dependent transcription. Although CbpA is highly regulated by Vfr, deletion of cbpA did not affect known Vfr-dependent functions, including the T2SS, the T3SS, flagellum- or TFP-dependent motility, virulence in a mouse model of acute pneumonia, or protein expression profiles. Unexpectedly, CbpA-green fluorescent protein was found to be localized to the flagellated old cell pole in a cAMP-dependent manner. These results suggest that polar localization of CbpA may be important for its function.
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Lo AW, Seers CA, Boyce JD, Dashper SG, Slakeski N, Lissel JP, Reynolds EC. Comparative transcriptomic analysis of Porphyromonas gingivalis biofilm and planktonic cells. BMC Microbiol 2009; 9:18. [PMID: 19175941 PMCID: PMC2637884 DOI: 10.1186/1471-2180-9-18] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2008] [Accepted: 01/29/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Porphyromonas gingivalis in subgingival dental plaque, as part of a mature biofilm, has been strongly implicated in the onset and progression of chronic periodontitis. In this study using DNA microarray we compared the global gene expression of a P. gingivalis biofilm with that of its planktonic counterpart grown in the same continuous culture. RESULTS Approximately 18% (377 genes, at 1.5 fold or more, P-value < 0.01) of the P. gingivalis genome was differentially expressed when the bacterium was grown as a biofilm. Genes that were down-regulated in biofilm cells, relative to planktonic cells, included those involved in cell envelope biogenesis, DNA replication, energy production and biosynthesis of cofactors, prosthetic groups and carriers. A number of genes encoding transport and binding proteins were up-regulated in P. gingivalis biofilm cells. Several genes predicted to encode proteins involved in signal transduction and transcriptional regulation were differentially regulated and may be important in the regulation of biofilm growth. CONCLUSION This study analyzing global gene expression provides insight into the adaptive response of P. gingivalis to biofilm growth, in particular showing a down regulation of genes involved in growth and metabolic activity.
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Affiliation(s)
- Alvin W Lo
- Cooperative Research Centre for Oral Health Science, Melbourne Dental School and the Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria, Australia.
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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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Characterization of a yjjQ mutant of avian pathogenic Escherichia coli (APEC). Microbiology (Reading) 2008; 154:1082-1093. [DOI: 10.1099/mic.0.2007/015784-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Wiehlmann L, Munder A, Adams T, Juhas M, Kolmar H, Salunkhe P, Tümmler B. Functional genomics of Pseudomonas aeruginosa to identify habitat-specific determinants of pathogenicity. Int J Med Microbiol 2007; 297:615-23. [PMID: 17481950 DOI: 10.1016/j.ijmm.2007.03.014] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2006] [Revised: 03/14/2007] [Accepted: 03/15/2007] [Indexed: 11/26/2022] Open
Abstract
Half of all genes in the Pseudomonas aeruginosa genome have either no homology to any previously reported sequence or are homologues of previously reported genes of unknown function. The signature-tagged mutagenesis (STM) screening method allows to explore the role of these hypothetical and unknown proteins for the colonization and persistence of P. aeruginosa in eukaryotic hosts. A plasposon STM library was constructed in the virulent clinical P. aeruginosa isolate TBCF10839 that can persist in polymorphonuclear leukocytes (PMNs). The STM library was screened for plasposon mutants that were attenuated in the killing of the nematode Caenorhabditis elegans, deficient in quorum sensing and production of type II secretion effector proteins or had become more susceptible to killing by PMNs in phagocytosis assays. The three screens revealed in total 69 attenuated mutants. Fifteen mutants that carried the transposon in potential novel virulence determinants of yet unknown function were selected for further analysis. The mutants were characterized in their transcriptome and proteome and their cytotoxicity in vitro and their virulence in worm and mouse infection models in vivo. Previous studies had revealed a remarkable degree of conservation in the virulence mechanisms used by P. aeruginosa to infect hosts of divergent evolutionary origins. Testing of our novel targets did not reveal such a strict conservation. The functional characterization revealed that the fifteen proteins play highly diverse roles in the cell and become habitat-specific virulence factors upon exposure to specific hosts and/or upon exposure to specific stress conditions or host defense mechanisms.
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Affiliation(s)
- Lutz Wiehlmann
- Klinische Forschergruppe, Abteilung Pädiatrische Pneumologie und Neonatologie, OE 6710, Medizinische Hochschule Hannover, Carl-Neuberg-Strass1, D-30625 Hannover, Germany
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Williams P, Winzer K, Chan WC, Cámara M. Look who's talking: communication and quorum sensing in the bacterial world. Philos Trans R Soc Lond B Biol Sci 2007; 362:1119-34. [PMID: 17360280 PMCID: PMC2435577 DOI: 10.1098/rstb.2007.2039] [Citation(s) in RCA: 494] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
For many years bacteria were considered primarily as autonomous unicellular organisms with little capacity for collective behaviour. However, we now appreciate that bacterial cells are in fact, highly communicative. The generic term 'quorum sensing' has been adopted to describe the bacterial cell-to-cell communication mechanisms which co-ordinate gene expression usually, but not always, when the population has reached a high cell density. Quorum sensing depends on the synthesis of small molecules (often referred to as pheromones or autoinducers) that diffuse in and out of bacterial cells. As the bacterial population density increases, so does the synthesis of quorum sensing signal molecules, and consequently, their concentration in the external environment rises. Once a critical threshold concentration has been reached, a target sensor kinase or response regulator is activated (or repressed) so facilitating the expression of quorum sensing-dependent genes. Quorum sensing enables a bacterial population to mount a co-operative response that improves access to nutrients or specific environmental niches, promotes collective defence against other competitor prokaryotes or eukaryotic defence mechanisms and facilitates survival through differentiation into morphological forms better able to combat environmental threats. Quorum sensing also crosses the prokaryotic-eukaryotic boundary since quorum sensing-dependent signalling can be exploited or inactivated by both plants and mammals.
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Affiliation(s)
- Paul Williams
- Institute of Infection, Immunity and Inflammation, Centre for Biomolecular Sciences, School of Molecular Medical Sciences, University of Nottingham, Nottingham NG7 2RD, UK.
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Wagner VE, Li LL, Isabella VM, Iglewski BH. Analysis of the hierarchy of quorum-sensing regulation in Pseudomonas aeruginosa. Anal Bioanal Chem 2006; 387:469-79. [PMID: 17139483 DOI: 10.1007/s00216-006-0964-6] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2006] [Revised: 10/25/2006] [Accepted: 10/25/2006] [Indexed: 10/23/2022]
Abstract
Quorum-sensing in Pseudomonas aeruginosa is known to regulate several aspects of pathogenesis, including virulence factor production, biofilm development, and antimicrobial resistance. Recent high-throughput analysis has revealed the existence of several layers of regulation within the QS-circuit. To address this complexity, mutations in genes encoding known or putative transcriptional regulators that were also identified as being regulated by the las and/or rhl QS systems were screened for their contribution in mediating several phenotypes, for example motility, secreted virulence products, and pathogenic capacity in a lettuce leaf model. These studies have further elucidated the potential contribution to virulence of these genes within the QS regulon.
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Affiliation(s)
- Victoria E Wagner
- Department of Microbiology and Immunology, School of Medicine and Dentistry, University of Rochester, Box 672, Rochester, NY 14642, USA
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Carty NL, Layland N, Colmer-Hamood JA, Calfee MW, Pesci EC, Hamood AN. PtxR modulates the expression of QS-controlled virulence factors in the Pseudomonas aeruginosa strain PAO1. Mol Microbiol 2006; 61:782-94. [PMID: 16803594 DOI: 10.1111/j.1365-2958.2006.05269.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The production of several virulence factors by Pseudomonas aeruginosa is regulated through the hierarchical cell-density dependent quorum sensing (QS) systems las and rhl. A third component of the QS hierarchy, the Pseudomonas quinolone signal PQS, also controls the expression of several genes. We previously described P. aeruginosa PtxR as a transcriptional activator of the exotoxin A gene toxA. Here, we provide evidence that PtxR regulates the production of other virulence factors. Mutation of ptxR in PAO1 increased pyocyanin production. This increase was reduced in the presence of a ptxR plasmid. Throughout the growth cycle, PtxR reduced the expression of the pyocyanin operon phzA1-G1 but not phzA2-G2. As pyocyanin production is stringently controlled by QS, we examined the effect of PtxR on QS-related genes in PAO1. PtxR also reduced the expression of the PQS synthesis operon pqsABCDE. ptxR mutation increased the expression of the rhamnolipid synthesis gene rhlA but decreased lasB expression. The expression of the RhlI synthase gene rhlI and the production of the C(4)-HSL autoinducer were increased in the ptxR mutant, while the expression of the LasI synthase gene lasI and the production of 3OC(12)-HSL were reduced. These results suggest that PtxR negatively regulates the expression of the rhamnolipid and pyocyanin genes through rhlI and the pqsABCDE operon while it positively regulates the expression of lasB through lasI.
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Affiliation(s)
- Nancy L Carty
- Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, TX 79430-5907, USA
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