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Li R, Zhu X, Zhang P, Wu X, Jin Q, Pan J. Ser/Thr protein kinase Stk1 phosphorylates the key transcriptional regulator AlgR to modulate virulence and resistance in Pseudomonas aeruginosa. Virulence 2024; 15:2367649. [PMID: 38898809 PMCID: PMC11197903 DOI: 10.1080/21505594.2024.2367649] [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: 01/25/2024] [Accepted: 06/09/2024] [Indexed: 06/21/2024] Open
Abstract
Pseudomonas aeruginosa is one of the leading causes of nosocomial infections worldwide and has emerged as a serious public health threat, due in large part to its multiple virulence factors and remarkable resistance capabilities. Stk1, a eukaryotic-type Ser/Thr protein kinase, has been shown in our previous work to be involved in the regulation of several signalling pathways and biological processes. Here, we demonstrate that deletion of stk1 leads to alterations in several virulence- and resistance-related physiological functions, including reduced pyocyanin and pyoverdine production, attenuated twitching motility, and enhanced biofilm production, extracellular polysaccharide secretion, and antibiotic resistance. Moreover, we identified AlgR, an important transcriptional regulator, as a substrate for Stk1, with its phosphorylation at the Ser143 site catalysed by Stk1. Intriguingly, both the deletion of stk1 and the mutation of Ser143 of AlgR to Ala result in similar changes in the above-mentioned physiological functions. Furthermore, assays of algR expression in these strains suggest that changes in the phosphorylation state of AlgR, rather than its expression level, underlie changes in these physiological functions. These findings uncover Stk1-mediated phosphorylation of AlgR as an important mechanism for regulating virulence and resistance in P. aeruginosa.
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Affiliation(s)
- Rui Li
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
| | - Xuan Zhu
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
| | - Pengfei Zhang
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
| | - Xuan Wu
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
| | - Qian Jin
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
| | - Jianyi Pan
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
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2
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Majdi C, Meffre P, Benfodda Z. Recent advances in the development of bacterial response regulators inhibitors as antibacterial and/or antibiotic adjuvant agent: A new approach to combat bacterial resistance. Bioorg Chem 2024; 150:107606. [PMID: 38968903 DOI: 10.1016/j.bioorg.2024.107606] [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: 03/25/2024] [Revised: 06/21/2024] [Accepted: 06/28/2024] [Indexed: 07/07/2024]
Abstract
The number of new antibacterial agents currently being discovered is insufficient to combat bacterial resistance. It is extremely challenging to find new antibiotics and to introduce them to the pharmaceutical market. Therefore, special attention must be given to find new strategies to combat bacterial resistance and prevent bacteria from developing resistance. Two-component system is a transduction system and the most prevalent mechanism employed by bacteria to respond to environmental changes. This signaling system consists of a membrane sensor histidine kinase that perceives environmental stimuli and a response regulator which acts as a transcription factor. The approach consisting of developing response regulators inhibitors with antibacterial activity or antibiotic adjuvant activity is a novel approach that has never been previously reviewed. In this review we report for the first time, the importance of targeting response regulators and summarizing all existing studies carried out from 2008 until now on response regulators inhibitors as antibacterial agents or / and antibiotic adjuvants. Moreover, we describe the antibacterial activity and/or antibiotic adjuvants activity against the studied bacterial strains and the mechanism of different response regulator inhibitors when it's possible.
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3
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Rajewska M, Maciąg T, Narajczyk M, Jafra S. Carbon Source and Substrate Surface Affect Biofilm Formation by the Plant-Associated Bacterium Pseudomonas donghuensis P482. Int J Mol Sci 2024; 25:8351. [PMID: 39125921 PMCID: PMC11312691 DOI: 10.3390/ijms25158351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2024] [Revised: 07/25/2024] [Accepted: 07/26/2024] [Indexed: 08/12/2024] Open
Abstract
The ability of bacteria to colonize diverse environmental niches is often linked to their competence in biofilm formation. It depends on the individual characteristics of a strain, the nature of the colonized surface (abiotic or biotic), or the availability of certain nutrients. Pseudomonas donghuensis P482 efficiently colonizes the rhizosphere of various plant hosts, but a connection between plant tissue colonization and the biofilm formation ability of this strain has not yet been established. We demonstrate here that the potential of P482 to form biofilms on abiotic surfaces and the structural characteristics of the biofilm are influenced by the carbon source available to the bacterium, with glycerol promoting the process. Also, the type of substratum, polystyrene or glass, impacts the ability of P482 to attach to the surface. Moreover, P482 mutants in genes associated with motility or chemotaxis, the synthesis of polysaccharides, and encoding proteases or regulatory factors, which affect biofilm formation on glass, were fully capable of colonizing the root tissue of both tomato and maize hosts. Investigating the role of cellular factors in biofilm formation using these plant-associated bacteria shows that the ability of bacteria to form biofilm on abiotic surfaces does not necessarily mirror its ability to colonize plant tissues. Our research provides a broader perspective on the adaptation of these bacteria to various environments.
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Affiliation(s)
- Magdalena Rajewska
- Laboratory of Plant Microbiology, Intercollegiate Faculty of Biotechnology of University of Gdansk and Medical University of Gdansk, Abrahama 58, 80-307 Gdansk, Poland;
| | - Tomasz Maciąg
- Institute of Biology, Department of Botany, Warsaw University of Life Sciences, Nowoursynowska 159, 02-776 Warsaw, Poland;
| | - Magdalena Narajczyk
- Laboratory of Electron Microscopy, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland;
| | - Sylwia Jafra
- Laboratory of Plant Microbiology, Intercollegiate Faculty of Biotechnology of University of Gdansk and Medical University of Gdansk, Abrahama 58, 80-307 Gdansk, Poland;
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Yalkut K, Ben Ali Hassine S, Basaran E, Kula C, Ozcan A, Avci FG, Keskin O, Sariyar Akbulut B, Ozbek P. Attenuation of Type IV pili activity by natural products. J Biomol Struct Dyn 2024:1-11. [PMID: 38305801 DOI: 10.1080/07391102.2024.2310781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Accepted: 01/20/2024] [Indexed: 02/03/2024]
Abstract
The virulence factor Type IV pili (T4P) are surface appendages used by the opportunistic pathogen Pseudomonas aeruginosa for twitching motility and adhesion in the environment and during infection. Additionally, the use of these appendages by P. aeruginosa for biofilm formation increases its virulence and drug resistance. Therefore, attenuation of the activity of T4P would be desirable to control P. aeruginosa infections. Here, a computational approach has been pursued to screen natural products that can be used for this purpose. PilB, the elongation ATPase of the T4P machinery in P. aeruginosa, has been selected as the target subunit and virtual screening of FDA-approved drugs has been conducted. Screening identified two natural compounds, ergoloid and irinotecan, as potential candidates for inhibiting this T4P-associated ATPase in P. aeruginosa. These candidate compounds underwent further rigorous evaluation through molecular dynamics (MD) simulations and then through in vitro twitching motility and biofilm inhibition assays. Notably, ergoloid emerged as a particularly promising candidate for weakening the T4P activity by inhibiting the elongation ATPases associated with T4P. This repurposing study paves the way for the timely discovery of antivirulence drugs as an alternative to classical antibiotic treatments to help combat infections caused by P. aeruginosa and related pathogens.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Kerem Yalkut
- Department of Bioengineering, Faculty of Engineering, Marmara University, Istanbul, Turkey
| | - Soumaya Ben Ali Hassine
- Department of Bioengineering, Faculty of Engineering, Marmara University, Istanbul, Turkey
- Department of Bioengineering, Faculty of Engineering and Natural Sciences, Uskudar University, Istanbul, Turkey
| | - Esra Basaran
- Graduate School of Sciences and Engineering, Koc University, Istanbul, Turkey
| | - Ceyda Kula
- Department of Bioengineering, Faculty of Engineering, Marmara University, Istanbul, Turkey
| | - Aslıhan Ozcan
- Department of Bioengineering, Faculty of Engineering, Marmara University, Istanbul, Turkey
| | - Fatma Gizem Avci
- Department of Bioengineering, Faculty of Engineering and Natural Sciences, Uskudar University, Istanbul, Turkey
| | - Ozlem Keskin
- Graduate School of Sciences and Engineering, Koc University, Istanbul, Turkey
| | - Berna Sariyar Akbulut
- Department of Bioengineering, Faculty of Engineering, Marmara University, Istanbul, Turkey
| | - Pemra Ozbek
- Department of Bioengineering, Faculty of Engineering, Marmara University, Istanbul, Turkey
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5
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Zhang Y, Bhasme P, Reddy DS, Liu D, Yu Z, Zhao T, Zheng Y, Kumar A, Yu H, Ma LZ. Dual functions: A coumarin-chalcone conjugate inhibits cyclic-di-GMP and quorum-sensing signaling to reduce biofilm formation and virulence of pathogens. MLIFE 2023; 2:283-294. [PMID: 38817812 PMCID: PMC10989777 DOI: 10.1002/mlf2.12087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 08/01/2023] [Indexed: 06/01/2024]
Abstract
Antibiotic resistance or tolerance of pathogens is one of the most serious global public health threats. Bacteria in biofilms show extreme tolerance to almost all antibiotic classes. Thus, use of antibiofilm drugs without bacterial-killing effects is one of the strategies to combat antibiotic tolerance. In this study, we discovered a coumarin-chalcone conjugate C9, which can inhibit the biofilm formation of three common pathogens that cause nosocomial infections, namely, Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli, with the best antibiofilm activity against P. aeruginosa. Further investigations indicate that C9 decreases the synthesis of the key biofilm matrix exopolysaccharide Psl and bacterial second messenger cyclic-di-GMP. Meanwhile, C9 can interfere with the regulation of the quorum sensing (QS) system to reduce the virulence of P. aeruginosa. C9 treatment enhances the sensitivity of biofilm to several antibiotics and reduces the survival rate of P. aeruginosa under starvation or oxidative stress conditions, indicating its excellent potential for use as an antibiofilm-forming and anti-QS drug.
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Affiliation(s)
- Yu Zhang
- State Key Laboratory of Microbial Resources, Institute of MicrobiologyChinese Academy of SciencesBeijingChina
| | - Pramod Bhasme
- State Key Laboratory of Microbial Resources, Institute of MicrobiologyChinese Academy of SciencesBeijingChina
- University of Chinese Academy of SciencesBeijingChina
| | - Dinesh S. Reddy
- Centre for Nano and Material SciencesJain UniversityBangaloreKarnatakaIndia
| | - Dejian Liu
- State Key Laboratory of Microbial Resources, Institute of MicrobiologyChinese Academy of SciencesBeijingChina
- University of Chinese Academy of SciencesBeijingChina
| | - Zhaoxiao Yu
- State Key Laboratory of Microbial Resources, Institute of MicrobiologyChinese Academy of SciencesBeijingChina
| | - Tianhu Zhao
- State Key Laboratory of Microbial Resources, Institute of MicrobiologyChinese Academy of SciencesBeijingChina
| | - Yaqian Zheng
- State Key Laboratory of Microbial Resources, Institute of MicrobiologyChinese Academy of SciencesBeijingChina
- University of Chinese Academy of SciencesBeijingChina
| | - Amit Kumar
- Centre for Nano and Material SciencesJain UniversityBangaloreKarnatakaIndia
| | - Haiying Yu
- State Key Laboratory of Microbial Resources, Institute of MicrobiologyChinese Academy of SciencesBeijingChina
| | - Luyan Z. Ma
- State Key Laboratory of Microbial Resources, Institute of MicrobiologyChinese Academy of SciencesBeijingChina
- University of Chinese Academy of SciencesBeijingChina
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6
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Zhang J, Wu H, Wang D, Wang L, Cui Y, Zhang C, Zhao K, Ma L. Intracellular glycosyl hydrolase PslG shapes bacterial cell fate, signaling, and the biofilm development of Pseudomonas aeruginosa. eLife 2022; 11:e72778. [PMID: 35438634 PMCID: PMC9075953 DOI: 10.7554/elife.72778] [Citation(s) in RCA: 2] [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: 08/04/2021] [Accepted: 04/17/2022] [Indexed: 11/22/2022] Open
Abstract
Biofilm formation is one of most important causes leading to persistent infections. Exopolysaccharides are usually a main component of biofilm matrix. Genes encoding glycosyl hydrolases are often found in gene clusters that are involved in the exopolysaccharide synthesis. It remains elusive about the functions of intracellular glycosyl hydrolase and why a polysaccharide synthesis gene cluster requires a glycosyl hydrolase-encoding gene. Here, we systematically studied the physiologically relevant role of intracellular PslG, a glycosyl hydrolase whose encoding gene is co-transcribed with 15 psl genes, which is responsible for the synthesis of exopolysaccharide PSL, a key biofilm matrix polysaccharide in opportunistic pathogen Pseudomonas aeruginosa. We showed that lack of PslG or its hydrolytic activity in this opportunistic pathogen enhances the signaling function of PSL, changes the relative level of cyclic-di-GMP within daughter cells during cell division and shapes the localization of PSL on bacterial periphery, thus results in long chains of bacterial cells, fast-forming biofilm microcolonies. Our results reveal the important roles of intracellular PslG on the cell fate and biofilm development.
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Affiliation(s)
- Jingchao Zhang
- Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin UniversityTianjinChina
| | - Huijun Wu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of SciencesBeijingChina
- University of Chinese Academy of SciencesBeijingChina
| | - Di Wang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of SciencesBeijingChina
| | - Lanxin Wang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of SciencesBeijingChina
- University of Chinese Academy of SciencesBeijingChina
| | - Yifan Cui
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of SciencesBeijingChina
- University of Chinese Academy of SciencesBeijingChina
| | - Chenxi Zhang
- Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin UniversityTianjinChina
| | - Kun Zhao
- Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin UniversityTianjinChina
| | - Luyan Ma
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of SciencesBeijingChina
- University of Chinese Academy of SciencesBeijingChina
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7
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RetS Regulates Phage Infection in Pseudomonas aeruginosa via Modulating the GacS/GacA Two-Component System. J Virol 2022; 96:e0019722. [PMID: 35348363 DOI: 10.1128/jvi.00197-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
In Pseudomonas aeruginosa, the complex multisensing regulatory networks RetS-GacS/GacA have been demonstrated to play key roles in controlling the switch between planktonic and sessile lifestyles. However, whether this multisensing system is involved in the regulation of phage infection has not been investigated. Here, we provide a link between the sensors RetS/GacS and infection of phages vB_Pae_QDWS and vB_Pae_W3. Our data suggest that the sensors kinases RetS and GacS in Pseudomonas aeruginosa play opposite regulatory functions on phage infection. Mutation in retS increased phage resistance. Cellular levels of RsmY and RsmZ increased in PaΔretS and were positively correlated with phage resistance. Further analysis demonstrated that RetS regulated phage infection by affecting the type IV pilus (T4P)-mediated adsorption. The regulation of RetS on phage infection depends on the GacS/GacA two-component system and is likely a dynamic process in response to environmental signals. The findings offer additional support for the rapid emergence of phage resistance. IMPORTANCE Our knowledge on the molecular mechanisms behind bacterium-phage interactions remains limited. Our study reported that the complex multisensing regulatory networks RetS-GacS/GacA of Pseudomonas aeruginosa PAO1 play key roles in controlling phage infection. The main observation was that the mutation in RetS could result in increased phage resistance by reducing the type IV pilus-mediated phage adsorption. The bacterial defense strategy is generally applicable to various phages since many P. aeruginosa phages can use type IV pilus as their receptors. The results also suggest that the phage infection is likely to be regulated dynamically, which depends on the environmental stimuli. Reduction of the signals that RetS favors would increase phage resistance. Our study is particularly remarkable for uncovering a signal transduction system that was involved in phage infection, which may help in filling some knowledge gaps in this field.
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8
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Abstract
The opportunistic pathogen Pseudomonas aeruginosa relies upon type IV pili (Tfp) for host colonization and virulence. Tfp are retractile surface appendages that promote adherence to host tissue and mediate twitching motility, a form of surface-associated translocation. Tfp are composed of a major structural pilin protein (PilA), several less abundant, fiber-associated pilin-like proteins (FimU, PilV, PilW, PilX, and PilE), and a pilus-associated tip adhesin and surface sensor (PilY1). Several proteins critical for Tfp biogenesis and surface sensing are encoded by the fimU-pilVWXY1Y2E operon. Tfp biogenesis is regulated by the global transcription factor Vfr and its allosteric effector, cyclic AMP (cAMP). Our investigation into the basis for reduced Tfp production in cAMP/vfr mutants revealed a defect in the expression of the fimU operon. We found that cAMP/Vfr activation of the fimU operon occurs via direct binding of Vfr to a specific fimU promoter sequence. We also refined the role of the AlgZ/AlgR two-component system in fimU regulation by demonstrating that phosphorylation of the response regulator AlgR is required for maximal binding to the fimU promoter region in vitro. Vfr also regulates expression of the algZR operon, revealing an indirect regulatory loop affecting fimU operon transcription. Overall, these results demonstrate that two linked but independent regulatory systems couple the expression of Tfp biogenesis and surface sensing genes and highlight the regulatory complexity governing expression of P. aeruginosa virulence factors. IMPORTANCE Pseudomonas aeruginosa is an opportunistic pathogen responsible for a wide range of infections. An extensive repertoire of virulence factors aid in P. aeruginosa pathogenesis. Type IV pili (Tfp) play a critical role in host colonization and infection by promoting adherence to host tissue, facilitating twitching motility and mediating surface-associated behaviors. The fimU operon encodes several pilus-associated proteins that are essential for proper Tfp function and surface sensing. In this study, we report that linked but independent regulatory systems dictate Tfp biogenesis. We also demonstrated the importance of different phosphorylation states of the AlgZ/AlgR two-component system and its role in Tfp biogenesis. Overall, this study furthers our understanding of the complex regulatory mechanisms that govern the production of a critical and multifaceted virulence factor.
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9
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Zhu X, Feng C, Zhou L, Li Z, Zhang Y, Pan J. Impacts of Ser/Thr Protein Kinase Stk1 on the Proteome, Twitching Motility, and Competitive Advantage in Pseudomonas aeruginosa. Front Microbiol 2021; 12:738690. [PMID: 34733256 PMCID: PMC8560001 DOI: 10.3389/fmicb.2021.738690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 08/20/2021] [Indexed: 11/30/2022] Open
Abstract
Pseudomonas aeruginosa is a ubiquitous gram-negative bacterium in the environment and a leading cause of nosocomial infections worldwide. Therefore, it is listed by the WHO as a human pathogen that urgently needs the development of new antibacterial drugs. Recent findings have demonstrated that eukaryote-type Ser/Thr protein kinases play a vital role in regulating various bacterial physiological processes by catalyzing protein phosphorylation. Stk1 has proven to be a Ser/Thr protein kinase in P. aeruginosa. However, the regulatory roles of Stk1 have not yet been revealed. Thus, we constructed a stk1 knockout mutant (∆stk1) from the P. aeruginosa PAO1 strain and employed a Tandem Mass Tag (TMT) labeling-based quantitative proteomic strategy to characterize proteome-wide changes in response to the stk1 knockout. In total, 620 differentially expressed proteins, among which 288 proteins were upregulated and 332 proteins were downregulated, were identified in ∆stk1 compared with P. aeruginosa PAO1. A detailed bioinformatics analysis of these differentially expressed proteins was performed, including GO annotation, protein domain profile, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, subcellular localization and enrichment analysis. Notably, the downregulation of type IV pilus-related proteins and upregulation of T6SS-H1-related proteins were found in the ∆stk1 strain, and the results were corroborated by quantitative PCR at the mRNA level. Further experiments confirmed that the loss of stk1 weakens bacterial twitching motility and promotes a growth competition advantage, which are, respectively, mediated by type IV pilus-related proteins and T6SS-H1-related proteins. These findings contribute to a better understanding of the physiological role of Stk1, and proteomic data will help further investigations of the roles and mechanisms of Stk1 in P. aeruginosa, although the detailed regulation and mechanism of Stk1 still need to be revealed.
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Affiliation(s)
- Xuan Zhu
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
| | - Chao Feng
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
| | - Lantian Zhou
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
| | - Zhenzhen Li
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
| | - Yue Zhang
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
| | - Jianyi Pan
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
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10
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The Two-Component System RstA/RstB Regulates Expression of Multiple Efflux Pumps and Influences Anaerobic Nitrate Respiration in Pseudomonas fluorescens. mSystems 2021; 6:e0091121. [PMID: 34726491 PMCID: PMC8562477 DOI: 10.1128/msystems.00911-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Multidrug resistance (MDR) efflux pumps are involved in bacterial intrinsic resistance to multiple antimicrobials. Expression of MDR efflux pumps can be either constitutive or transiently induced by various environmental signals, which are typically perceived by bacterial two-component systems (TCSs) and relayed to the bacterial nucleoid, where gene expression is modulated for niche adaptation. Here, we demonstrate that RstA/RstB, a TCS previously shown to control acid-induced and biofilm-related genes in Escherichiacoli, confers resistance to multiple antibiotics in Pseudomonas fluorescens by directly regulating the MDR efflux pumps EmhABC and MexCD-OprJ. Moreover, we show that phosphorylation of the conserved Asp52 residue in RstA greatly enhances RstA-DNA interaction, and regulation of the multidrug resistance by RstA/RstB is dependent on the phosphorylation of the RstA Asp52 residue by RstB. Proteome analysis reveals RstA/RstB also positively regulates the efflux pump MexEF-OprN and enzymes involved in anaerobic nitrate respiration and pyoverdine biosynthesis. Our results suggest that, by coupling the expression of multiple efflux pumps and anaerobic nitrate respiration, RstA/RstB could play a role in defense against nitrosative stress caused by anaerobic nitrate respiration. IMPORTANCE Microenvironmental hypoxia typically increases bacterial multidrug resistance by elevating expression of multidrug efflux pumps, but the precise mechanism is currently not well understood. Here, we showed that the two-component system RstA/RstB not only positively regulated expression of several efflux pumps involved in multidrug resistance, but also promoted expression of enzymes involved in anaerobic nitrate respiration and pyoverdine biosynthesis. These results suggested that, by upregulating expression of efflux pumps and pyoverdine biosynthesis-related enzymes, RstA/RstB could play a role in promoting bacterial tolerance to hypoxia by providing protection against nitrosative stress.
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11
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Zhou T, Huang J, Liu Z, Xu Z, Zhang LH. Molecular Mechanisms Underlying the Regulation of Biofilm Formation and Swimming Motility by FleS/FleR in Pseudomonas aeruginosa. Front Microbiol 2021; 12:707711. [PMID: 34367113 PMCID: PMC8335546 DOI: 10.3389/fmicb.2021.707711] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 06/28/2021] [Indexed: 11/18/2022] Open
Abstract
Pseudomonas aeruginosa, a major cause of nosocomial infection, can survive under diverse environmental conditions. Its great adaptive ability is dependent on its multiple signaling systems such as the two-component system (TCS). A TCS FleS/FleR has been previously identified to positively regulate a variety of virulence-related traits in P. aeruginosa PAO1 including motility and biofilm formation which are involved in the acute and chronic infections, respectively. However, the molecular mechanisms underlying these regulations are still unclear. In this study, we first analyzed the regulatory roles of each domains in FleS/FleR and characterized key residues in the FleS-HisKA, FleR-REC and FleR-AAA domains that are essential for the signaling. Next, we revealed that FleS/FleR regulates biofilm formation in a c-di-GMP and FleQ dependent manner. Lastly, we demonstrated that FleR can regulate flagellum biosynthesis independently without FleS, which explains the discrepant regulation of swimming motility by FleS and FleR.
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Affiliation(s)
- Tian Zhou
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China.,Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Center, South China Agricultural University, Guangzhou, China
| | - Jiahui Huang
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China.,Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Center, South China Agricultural University, Guangzhou, China
| | - Zhiqing Liu
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China.,Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Center, South China Agricultural University, Guangzhou, China
| | - Zeling Xu
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China.,Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Center, South China Agricultural University, Guangzhou, China
| | - Lian-Hui Zhang
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China.,Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Center, South China Agricultural University, Guangzhou, China
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12
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Penaranda C, Chumbler NM, Hung DT. Dual transcriptional analysis reveals adaptation of host and pathogen to intracellular survival of Pseudomonas aeruginosa associated with urinary tract infection. PLoS Pathog 2021; 17:e1009534. [PMID: 33901267 PMCID: PMC8102004 DOI: 10.1371/journal.ppat.1009534] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 05/06/2021] [Accepted: 04/06/2021] [Indexed: 11/21/2022] Open
Abstract
Long-term survival of bacterial pathogens during persistent bacterial infections can be associated with antibiotic treatment failure and poses a serious public health problem. Infections caused by the Gram-negative pathogen Pseudomonas aeruginosa, which can cause both acute and chronic infections, are particularly challenging due to its high intrinsic resistance to antibiotics. The ineffectiveness of antibiotics is exacerbated when bacteria reside intracellularly within host cells where they can adopt a drug tolerant state. While the early steps of adherence and entry of P. aeruginosa into mammalian cells have been described, the subsequent fate of internalized bacteria, as well as host and bacterial molecular pathways facilitating bacterial long-term survival, are not well defined. In particular, long-term survival within bladder epithelial cells has not been demonstrated and this may have important implications for the understanding and treatment of UTIs caused by P. aeruginosa. Here, we demonstrate and characterize the intracellular survival of wild type (WT) P. aeruginosa inside bladder epithelial cells and a mutant with a disruption in the bacterial two-component regulator AlgR that is unable to survive intracellularly. Using simultaneous dual RNA-seq transcriptional profiling, we define the transcriptional response of intracellular bacteria and their corresponding invaded host cells. The bacterial transcriptional response demonstrates that WT bacteria rapidly adapt to the stress encountered in the intracellular environment in contrast to ΔalgR bacteria. Analysis of the host transcriptional response to invasion suggests that the NF-κB signaling pathway, previously shown to be required for extracellular bacterial clearance, is paradoxically also required for intracellular bacterial survival. Lastly, we demonstrate that intracellular survival is important for pathogenesis of P. aeruginosa in vivo using a model of murine urinary tract infection. We propose that the unappreciated ability of P. aeruginosa to survive intracellularly may play an important role in contributing to the chronicity and recurrence of P. aeruginosa in urinary tract infections. Chronic persistent bacterial infections are a serious and growing public health problem worsened by the rise in antibiotic resistance, yet new approaches for treating these infections are lacking. These long-term infections can occur when bacteria invade and survive inside host cells where they can hide from the immune system and become less susceptible to killing by antibiotics. Pseudomonas aeruginosa, a bacterium conventionally considered an extracellular pathogen, can cause chronic infections of many organ systems, including the urinary tract. Here, we show that P. aeruginosa can in fact survive inside bladder epithelial cells and becomes tolerant to antibiotic treatment. Using gene expression analysis, we show that bacteria quickly adapt to the intracellular environment while the corresponding host cells upregulate the NF-κB signaling pathway. We demonstrate that this response, which had previously been shown to be required for clearance of extracellular bacteria, is paradoxically also required for survival of intracellular bacteria. We propose that the ability of P. aeruginosa to survive intracellularly plays an important role in contributing to the chronicity and recurrence of P. aeruginosa infections and that targeting host pathways, such as NF-κB signaling, could transform our ability to manage chronic and/or recurrent infections.
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Affiliation(s)
- Cristina Penaranda
- Infectious Disease and Microbiome Program, Broad Institute of Harvard and MIT, Cambridge, Massachusetts, United States of America
- Department of Molecular Biology and Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Nicole M. Chumbler
- Infectious Disease and Microbiome Program, Broad Institute of Harvard and MIT, Cambridge, Massachusetts, United States of America
- Department of Molecular Biology and Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Deborah T. Hung
- Infectious Disease and Microbiome Program, Broad Institute of Harvard and MIT, Cambridge, Massachusetts, United States of America
- Department of Molecular Biology and Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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Wilson T, Mouriño S, Wilks A. The heme-binding protein PhuS transcriptionally regulates the Pseudomonas aeruginosa tandem sRNA prrF1,F2 locus. J Biol Chem 2021; 296:100275. [PMID: 33428928 PMCID: PMC7948967 DOI: 10.1016/j.jbc.2021.100275] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 01/04/2021] [Accepted: 01/07/2021] [Indexed: 11/18/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen requiring iron for its survival and virulence. P. aeruginosa can acquire iron from heme via the nonredundant heme assimilation system and Pseudomonas heme uptake (Phu) systems. Heme transported by either the heme assimilation system or Phu system is sequestered by the cytoplasmic protein PhuS. Furthermore, PhuS has been shown to specifically transfer heme to the iron-regulated heme oxygenase HemO. As the PhuS homolog ShuS from Shigella dysenteriae was observed to bind DNA as a function of its heme status, we sought to further determine if PhuS, in addition to its role in regulating heme flux through HemO, functions as a DNA-binding protein. Herein, through a combination of chromatin immunoprecipitation–PCR, EMSA, and fluorescence anisotropy, we show that apo-PhuS but not holo-PhuS binds upstream of the tandem iron-responsive sRNAs prrF1,F2. Previous studies have shown the PrrF sRNAs are required for sparing iron for essential proteins during iron starvation. Furthermore, under certain conditions, a heme-dependent read through of the prrF1 terminator yields the longer PrrH transcript. Quantitative PCR analysis of P. aeruginosa WT and ΔphuS strains shows that loss of PhuS abrogates the heme-dependent regulation of PrrF and PrrH levels. Taken together, our data show that PhuS, in addition to its role in extracellular heme metabolism, also functions as a transcriptional regulator by modulating PrrF and PrrH levels in response to heme. This dual function of PhuS is central to integrating extracellular heme utilization into the PrrF/PrrH sRNA regulatory network that is critical for P. aeruginosa adaptation and virulence within the host.
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Affiliation(s)
- Tyree Wilson
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland, USA
| | - Susana Mouriño
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland, USA
| | - Angela Wilks
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland, USA.
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Cyclic di-GMP-Mediated Regulation of Extracellular Mannuronan C-5 Epimerases Is Essential for Cyst Formation in Azotobacter vinelandii. J Bacteriol 2020; 202:JB.00135-20. [PMID: 32989089 DOI: 10.1128/jb.00135-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 09/23/2020] [Indexed: 11/20/2022] Open
Abstract
The genus Azotobacter, belonging to the Pseudomonadaceae family, is characterized by the formation of cysts, which are metabolically dormant cells produced under adverse conditions and able to resist desiccation. Although this developmental process has served as a model for the study of cell differentiation in Gram-negative bacteria, the molecular basis of its regulation is still poorly understood. Here, we report that the ubiquitous second messenger cyclic dimeric GMP (c-di-GMP) is critical for the formation of cysts in Azotobacter vinelandii Upon encystment induction, the levels of c-di-GMP increased, reaching a peak within the first 6 h. In the absence of the diguanylate cyclase MucR, however, the levels of this second messenger remained low throughout the developmental process. A. vinelandii cysts are surrounded by two alginate layers with variable proportions of guluronic residues, which are introduced into the final alginate chain by extracellular mannuronic C-5 epimerases of the AlgE1 to AlgE7 family. Unlike in Pseudomonas aeruginosa, MucR was not required for alginate polymerization in A. vinelandii Conversely, MucR was necessary for the expression of extracellular alginate C-5 epimerases; therefore, the MucR-deficient strain produced cyst-like structures devoid of the alginate capsule and unable to resist desiccation. Expression of mucR was partially dependent on the response regulator AlgR, which binds to two sites in the mucR promoter, enhancing mucR transcription. Together, these results indicate that the developmental process of A. vinelandii is controlled through a signaling module that involves activation by the response regulator AlgR and c-di-GMP accumulation that depends on MucR.IMPORTANCE A. vinelandii has served as an experimental model for the study of the differentiation processes to form metabolically dormant cells in Gram-negative bacteria. This work identifies c-di-GMP as a critical regulator for the production of alginates with specific contents of guluronic residues that are able to structure the rigid laminated layers of the cyst envelope. Although allosteric activation of the alginate polymerase complex Alg8-Alg44 by c-di-GMP has long been recognized, our results show a previously unidentified role during the polymer modification step, controlling the expression of extracellular alginate epimerases. Our results also highlight the importance of c-di-GMP in the control of the physical properties of alginate, which ultimately determine the desiccation resistance of the differentiated cell.
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15
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Badal D, Jayarani AV, Kollaran MA, Kumar A, Singh V. Pseudomonas aeruginosa biofilm formation on endotracheal tubes requires multiple two-component systems. J Med Microbiol 2020; 69:906-919. [PMID: 32459613 DOI: 10.1099/jmm.0.001199] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Introduction. Indwelling medical devices such as endotracheal tubes (ETTs), urinary catheters, vascular access devices, tracheostomies and feeding tubes are often associated with hospital-acquired infections. Bacterial biofilm formed on the ETTs in intubated patients is a significant risk factor associated with ventilator-associated pneumonia. Pseudomonas aeruginosa is one of the four frequently encountered bacteria responsible for causing pneumonia, and the biofilm formation on ETTs. However, understanding of biofilm formation on ETT and interventions to prevent biofilm remains lagging. The ability to sense and adapt to external cues contributes to their success. Thus, the biofilm formation is likely to be influenced by the two-component systems (TCSs) that are composed of a membrane-associated sensor kinase and an intracellular response regulator.Aim. This study aims to establish an in vitro method to analyse the P. aeruginosa biofilm formation on ETTs, and identify the TCSs that contribute to this process.Methodology. In total, 112 P. aeruginosa PA14 TCS mutants were tested for their ability to form biofilm on ETTs, their effect on quorum sensing (QS) and motility.Results. Out of 112 TCS mutants studied, 56 had altered biofilm biomass on ETTs. Although the biofilm formation on ETTs is QS-dependent, none of the 56 loci controlled quorum signal. Of these, 18 novel TCSs specific to ETT biofilm were identified, namely, AauS, AgtS, ColR, CopS, CprR, NasT, KdpD, ParS, PmrB, PprA, PvrS, RcsC, PA14_11120, PA14_32580, PA14_45880, PA14_49420, PA14_52240, PA14_70790. The set of 56 included the GacS network, TCS proteins involved in fimbriae synthesis, TCS proteins involved in antimicrobial peptide resistance, and surface-sensing. Additionally, several of the TCS-encoding genes involved in biofilm formation on ETTs were found to be linked to flagellum-dependent swimming motility.Conclusions. Our study established an in vitro method for studying P. aeruginosa biofilm formation on the ETT surfaces. We also identified novel ETT-specific TCSs that could serve as targets to prevent biofilm formation on indwelling devices frequently used in clinical settings.
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Affiliation(s)
- Divakar Badal
- Department of Biosystems Sciences and Engineering, Indian Institute of Science, Bangalore, Karnataka, INDIA
| | - Abhijith Vimal Jayarani
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, Karnataka, INDIA
| | - Mohammed Ameen Kollaran
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, Karnataka, INDIA
| | - Aloke Kumar
- Department of Mechanical Engineering, Indian Institute of Science, Bangalore, Karnataka, INDIA.,Department of Biosystems Sciences and Engineering, Indian Institute of Science, Bangalore, Karnataka, INDIA
| | - Varsha Singh
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, Karnataka, INDIA.,Department of Biosystems Sciences and Engineering, Indian Institute of Science, Bangalore, Karnataka, INDIA
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16
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Xu A, Zhang M, Du W, Wang D, Ma LZ. A molecular mechanism for how sigma factor AlgT and transcriptional regulator AmrZ inhibit twitching motility in Pseudomonas aeruginosa. Environ Microbiol 2020; 23:572-587. [PMID: 32162778 DOI: 10.1111/1462-2920.14985] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2019] [Revised: 02/27/2020] [Accepted: 03/10/2020] [Indexed: 11/28/2022]
Abstract
Pseudomonas aeruginosa isolates from cystic fibrosis patients are often mucoid (due to the overexpression of exopolysaccharide alginate) yet lost motility. It remains unclear about how P. aeruginosa coordinately regulates alginate production and the type IV pili-driven twitching motility. Here we showed that sigma 22 factor (AlgT/U), an activator of alginate biosynthesis, repressed twitching motility by inhibiting the expression of pilin (PilA) through the intermediate transcriptional regulator AmrZ, which directly bound to the promoter region of pilA in both mucoid strain FRD1 and non-mucoid strain PAO1. Four conserved AmrZ-binding sites were found in pilA promoters among 10 P. aeruginosa strains although their entire pilA promoters had low identity. AmrZ has been reported to be essential for twitching in PAO1. We found that AmrZ was also required for twitching in mucoid FRD1, yet a high level of AmrZ inhibited twitching motility. This result was consistent with the phenomenon that twitching is frequently repressed in mucoid strains, in which the expression of AmrZ was highly activated by AlgT. Additionally, AlgT also inhibited the transcription of pilMNOP operon, which is involved in efficient pilus assembly. Our data elucidated a mechanism for how AlgT and AmrZ coordinately controlled twitching motility in P. aeruginosa.
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Affiliation(s)
- Anming Xu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Miaokun Zhang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Weili Du
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Di Wang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Luyan Z Ma
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
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17
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Rosales-Hurtado M, Meffre P, Szurmant H, Benfodda Z. Synthesis of histidine kinase inhibitors and their biological properties. Med Res Rev 2019; 40:1440-1495. [PMID: 31802520 DOI: 10.1002/med.21651] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 11/20/2019] [Accepted: 11/23/2019] [Indexed: 11/11/2022]
Abstract
Infections caused by multidrug-resistant bacteria represent a significant and ever-increasing cause of morbidity and mortality. There is thus an urgent need to develop efficient and well-tolerated antibacterials targeting unique cellular processes. Numerous studies have led to the identification of new biological targets to fight bacterial resistance. Two-component signal transduction systems are widely employed by bacteria to translate external and cellular signals into a cellular response. They are ubiquitous in bacteria, absent in the animal kingdom and are integrated into various virulence pathways. Several chemical series, including isothiazolidones, imidazolium salts, benzoxazines, salicylanilides, thiophenes, thiazolidiones, benzimidazoles, and other derivatives deduced by different approaches have been reported in the literature to have histidine kinase (HK) inhibitory activity. In this review, we report on the design and the synthesis of these HKs inhibitors and their potential to serve as antibacterial agents.
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Affiliation(s)
| | | | - Hendrik Szurmant
- Department of Basic Medical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona, California
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18
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Biological synthesis of high-conductive pili in aerobic bacterium Pseudomonas aeruginosa. Appl Microbiol Biotechnol 2018; 103:1535-1544. [PMID: 30523372 DOI: 10.1007/s00253-018-9484-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 10/22/2018] [Indexed: 10/27/2022]
Abstract
Bioelectrical nanowires as ecomaterials have great potential on environmental applications. A wide range of bacteria can express type IV pili (T4P), which are long protein fibers assembled from PilA. The T4P of Geobacter sulfurreducens are well known as "microbial nanowires," yet T4P of Pseudomonas aeruginosa (PaT4P) was believed to be poorly conductive. P. aeruginosa is an aerobic and electrochemically active bacterium. Its T4P have been known to be responsible for surface attachment, twitching motility and biofilm formation. Here, we show that PaT4P can be highly conductive while assembled by a truncated P. aeruginosa PilA (PaPilA) containing only N-terminus 61 amino acids. Furthermore, increasing the number of aromatic amino acids in the PaPilA1-61 significantly enhances the conductivity of pili and the bioelectricity output of P. aeruginosa in microbial fuel cell system, suggesting a potential application of PaT4P as a conductive nanomaterial. The N-terminal region of PilA from diverse eubacteria is highly conserved, implying a general way to synthesize highly conductive microbial nanowires and to increase the bioelectricity output of microbial fuel cell.
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19
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Gaviard C, Jouenne T, Hardouin J. Proteomics ofPseudomonas aeruginosa: the increasing role of post-translational modifications. Expert Rev Proteomics 2018; 15:757-772. [DOI: 10.1080/14789450.2018.1516550] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Charlotte Gaviard
- Normandie Univ, UNIROUEN, INSA Rouen, CNRS, PBS, 76000, Rouen, France
- PISSARO proteomic facility, IRIB, 76821 Mont-Saint-Aignan, France
| | - Thierry Jouenne
- Normandie Univ, UNIROUEN, INSA Rouen, CNRS, PBS, 76000, Rouen, France
- PISSARO proteomic facility, IRIB, 76821 Mont-Saint-Aignan, France
| | - Julie Hardouin
- Normandie Univ, UNIROUEN, INSA Rouen, CNRS, PBS, 76000, Rouen, France
- PISSARO proteomic facility, IRIB, 76821 Mont-Saint-Aignan, France
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20
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Pseudomonas aeruginosa type IV minor pilins and PilY1 regulate virulence by modulating FimS-AlgR activity. PLoS Pathog 2018; 14:e1007074. [PMID: 29775484 PMCID: PMC5979040 DOI: 10.1371/journal.ppat.1007074] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 05/31/2018] [Accepted: 05/04/2018] [Indexed: 11/19/2022] Open
Abstract
Type IV pili are expressed by a wide range of prokaryotes, including the opportunistic pathogen Pseudomonas aeruginosa. These flexible fibres mediate twitching motility, biofilm maturation, surface adhesion, and virulence. The pilus is composed mainly of major pilin subunits while the low abundance minor pilins FimU-PilVWXE and the putative adhesin PilY1 prime pilus assembly and are proposed to form the pilus tip. The minor pilins and PilY1 are encoded in an operon that is positively regulated by the FimS-AlgR two-component system. Independent of pilus assembly, PilY1 was proposed to be a mechanosensory component that—in conjunction with minor pilins—triggers up-regulation of acute virulence phenotypes upon surface attachment. Here, we investigated the link between the minor pilins/PilY1 and virulence. pilW, pilX, and pilY1 mutants had reduced virulence towards Caenorhabditis elegans relative to wild type or a major pilin mutant, implying a role in pathogenicity that is independent of pilus assembly. We hypothesized that loss of specific minor pilins relieves feedback inhibition on FimS-AlgR, increasing transcription of the AlgR regulon and delaying C. elegans killing. Reporter assays confirmed that FimS-AlgR were required for increased expression of the minor pilin operon upon loss of select minor pilins. Overexpression of AlgR or its hyperactivation via a phosphomimetic mutation reduced virulence, and the virulence defects of pilW, pilX, and pilY1 mutants required FimS-AlgR expression and activation. We propose that PilY1 and the minor pilins inhibit their own expression, and that loss of these proteins leads to FimS-mediated activation of AlgR that suppresses expression of acute-phase virulence factors and delays killing. This mechanism could contribute to adaptation of P. aeruginosa in chronic lung infections, as mutations in the minor pilin operon result in the loss of piliation and increased expression of AlgR-dependent virulence factors–such as alginate–that are characteristic of such infections. Pseudomonas aeruginosa causes dangerous infections, including chronic lung infections in cystic fibrosis patients. It uses many strategies to infect its hosts, including deployment of grappling hook-like fibres called type IV pili. Among the components involved in assembly and function of the pilus are five proteins called minor pilins that—along with a larger protein called PilY1—may help the pilus attach to surfaces. In a roundworm infection model, loss of PilY1 and specific minor pilins delayed killing, while loss of other pilus components did not. We traced this effect to increased activation of the FimS-AlgR regulatory system that inhibits the expression of virulence factors used early in infection, while positively regulating chronic infection traits such as alginate production, a phenotype called mucoidy. A disruption in the appropriate timing of FimS-AlgR-dependent virulence factor expression when select minor pilins or PilY1 are missing may explain why those pilus-deficient mutants have reduced virulence compared with others whose products are not under FimS-AlgR control. Increased FimS-AlgR activity upon loss of PilY1 and specific minor pilins could help to explain the frequent co-occurrence of the non-piliated and mucoid phenotypes that are hallmarks of chronic P. aeruginosa lung infections.
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Little AS, Okkotsu Y, Reinhart AA, Damron FH, Barbier M, Barrett B, Oglesby-Sherrouse AG, Goldberg JB, Cody WL, Schurr MJ, Vasil ML, Schurr MJ. Pseudomonas aeruginosa AlgR Phosphorylation Status Differentially Regulates Pyocyanin and Pyoverdine Production. mBio 2018; 9:e02318-17. [PMID: 29382736 PMCID: PMC5790918 DOI: 10.1128/mbio.02318-17] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 12/18/2017] [Indexed: 12/31/2022] Open
Abstract
Pseudomonas aeruginosa employs numerous, complex regulatory elements to control expression of its many virulence systems. The P. aeruginosa AlgZR two-component regulatory system controls the expression of several crucial virulence phenotypes. We recently determined, through transcriptomic profiling of a PAO1 ΔalgR mutant strain compared to wild-type PAO1, that algZR and hemCD are cotranscribed and show differential iron-dependent gene expression. Previous expression profiling was performed in strains without algR and revealed that AlgR acts as either an activator or repressor, depending on the gene. Thus, examination of P. aeruginosa gene expression from cells locked into different AlgR phosphorylation states reveals greater physiological relevance. Therefore, gene expression from strains carrying algR alleles encoding a phosphomimetic (AlgR D54E) or a phosphoablative (AlgR D54N) form were compared by microarray to PAO1. Transcriptome analyses of these strains revealed 25 differentially expressed genes associated with iron siderophore biosynthesis or heme acquisition or production. The PAO1 algR D54N mutant produced lower levels of pyoverdine but increased expression of the small RNAs prrf1 and prrf2 compared to PAO1. In contrast, the algR D54N mutant produced more pyocyanin than wild-type PAO1. On the other hand, the PAO1 algR D54E mutant produced higher levels of pyoverdine, likely due to increased expression of an iron-regulated gene encoding the sigma factor pvdS, but it had decreased pyocyanin production. AlgR specifically bound to the prrf2 and pvdS promoters in vitro AlgR-dependent pyoverdine production was additionally influenced by carbon source rather than the extracellular iron concentration per se AlgR phosphorylation effects were also examined in a Drosophila melanogaster feeding, murine acute pneumonia, and punch wound infection models. Abrogation of AlgR phosphorylation attenuated P. aeruginosa virulence in these infection models. These results show that the AlgR phosphorylation state can directly, as well as indirectly, modulate the expression of iron acquisition genes that may ultimately impact the ability of P. aeruginosa to establish and maintain an infection.IMPORTANCE Pyoverdine and pyocyanin production are well-known P. aeruginosa virulence factors that obtain extracellular iron from the environment and from host proteins in different manners. Here, we show that the AlgR phosphorylation state inversely controls pyoverdine and pyocyanin production and that this control is carbon source dependent. P. aeruginosa expressing AlgR D54N, mimicking the constitutively unphosphorylated state, produced more pyocyanin than cells expressing wild-type AlgR. In contrast, a strain expressing an AlgR phosphomimetic (AlgR D54E) produced higher levels of pyoverdine. Pyoverdine production was directly controlled through the prrf2 small regulatory RNA and the pyoverdine sigma factor, PvdS. Abrogating pyoverdine or pyocyanin gene expression has been shown to attenuate virulence in a variety of models. Moreover, the inability to phosphorylate AlgR attenuates virulence in three different models, a Drosophila melanogaster feeding model, a murine acute pneumonia model, and a wound infection model. Interestingly, AlgR-dependent pyoverdine production was responsive to carbon source, indicating that this regulation has additional complexities that merit further study.
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Affiliation(s)
- Alexander S. Little
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Yuta Okkotsu
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Alexandria A. Reinhart
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - F. Heath Damron
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, West Virginia, USA
| | - Mariette Barbier
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, West Virginia, USA
| | - Brandon Barrett
- Department of Biology, University of Dallas, Irving, Texas, USA
| | - Amanda G. Oglesby-Sherrouse
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, USA
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Joanna B. Goldberg
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA
- Center for Cystic Fibrosis and Airways Disease Research, Children’s Healthcare of Atlanta, Atlanta, Georgia, USA
| | - William L. Cody
- Department of Biology, University of Dallas, Irving, Texas, USA
| | - Michael J. Schurr
- Department of Surgery, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Michael L. Vasil
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Michael J. Schurr
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
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22
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Chang CY. Surface Sensing for Biofilm Formation in Pseudomonas aeruginosa. Front Microbiol 2018; 8:2671. [PMID: 29375533 PMCID: PMC5767216 DOI: 10.3389/fmicb.2017.02671] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 12/21/2017] [Indexed: 11/13/2022] Open
Abstract
Aggregating and forming biofilms on biotic or abiotic surfaces are ubiquitous bacterial behaviors under various conditions. In clinical settings, persistent presence of biofilms increases the risks of healthcare-associated infections and imposes huge healthcare and economic burdens. Bacteria within biofilms are protected from external damage and attacks from the host immune system and can exchange genomic information including antibiotic-resistance genes. Dispersed bacterial cells from attached biofilms on medical devices or host tissues may also serve as the origin of further infections. Understanding how bacteria develop biofilms is pertinent to tackle biofilm-associated infections and transmission. Biofilms have been suggested as a continuum of growth modes for adapting to different environments, initiating from bacterial cells sensing their attachment to a surface and then switching cellular physiological status for mature biofilm development. It is crucial to understand bacterial gene regulatory networks and decision-making processes for biofilm formation upon initial surface attachment. Pseudomonas aeruginosa is one of the model microorganisms for studying bacterial population behaviors. Several hypotheses and studies have suggested that extracellular macromolecules and appendages play important roles in bacterial responses to the surface attachment. Here, I review recent studies on potential molecular mechanisms and signal transduction pathways for P. aeruginosa surface sensing.
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Affiliation(s)
- Chien-Yi Chang
- School of Chemistry and Biosciences, University of Bradford, Bradford, United Kingdom
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Regulation of ribonucleotide synthesis by the Pseudomonas aeruginosa two-component system AlgR in response to oxidative stress. Sci Rep 2017; 7:17892. [PMID: 29263410 PMCID: PMC5738425 DOI: 10.1038/s41598-017-17917-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 12/04/2017] [Indexed: 11/11/2022] Open
Abstract
Ribonucleotide reductases (RNR) catalyze the last step of deoxyribonucleotide synthesis, and are therefore essential to DNA-based life. Three forms of RNR exist: classes I, II, and III. While eukaryotic cells use only class Ia RNR, bacteria can harbor any combination of classes, granting them adaptability. The opportunistic pathogen Pseudomonas aeruginosa surprisingly encodes all three classes, allowing it to thrive in different environments. Here we study an aspect of the complex RNR regulation whose molecular mechanism has never been elucidated, the well-described induction through oxidative stress, and link it to the AlgZR two-component system, the primary regulator of the mucoid phenotype. Through bioinformatics, we identify AlgR binding locations in RNR promoters, which we characterize functionally through EMSA and physically through AFM imaging. Gene reporter assays in different growth models are used to study the AlgZR-mediated control on the RNR network under various environmental conditions and physiological states. Thereby, we show that the two-component system AlgZR, which is crucial for bacterial conversion to the mucoid phenotype associated with chronic disease, controls the RNR network and directs how the DNA synthesis pathway is modulated in mucoid and non-mucoid biofilms, allowing it to respond to oxidative stress.
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The Pseudomonas aeruginosa Two-Component Regulator AlgR Directly Activates rsmA Expression in a Phosphorylation-Independent Manner. J Bacteriol 2017; 199:JB.00048-17. [PMID: 28320883 DOI: 10.1128/jb.00048-17] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 03/13/2017] [Indexed: 02/07/2023] Open
Abstract
Pseudomonas aeruginosa is an important pathogen of the immunocompromised, causing both acute and chronic infections. In cystic fibrosis (CF) patients, P. aeruginosa causes chronic disease. The impressive sensory network of P. aeruginosa allows the bacterium to sense and respond to a variety of stimuli found in diverse environments. Transcriptional regulators, including alternative sigma factors and response regulators, integrate signals changing gene expression, allowing P. aeruginosa to cause infection. The two-component transcriptional regulator AlgR is important in P. aeruginosa pathogenesis in both acute and chronic infections. In chronic infections, AlgR and the alternative sigma factor AlgU activate the genes responsible for alginate production. Previous work demonstrated that AlgU controls rsmA expression. RsmA is a posttranscriptional regulator that is antagonized by two small RNAs, RsmY and RsmZ. In this work, we demonstrate that AlgR directly activates rsmA expression from the same promoter as AlgU. In addition, phosphorylation was not necessary for AlgR activation of rsmA using algR and algZ mutant strains. AlgU and AlgR appear to affect the antagonizing small RNAs rsmY and rsmZ indirectly. RsmA was active in a mucA22 mutant strain using leader fusions of two RsmA targets, tssA1 and hcnA AlgU and AlgR were necessary for posttranscriptional regulation of tssA1 and hcnA Altogether, our work demonstrates that the alginate regulators AlgU and AlgR are important in the control of the RsmA posttranscriptional regulatory system. These findings suggest that RsmA plays an unknown role in mucoid strains due to AlgU and AlgR activities.IMPORTANCE P. aeruginosa infections are difficult to treat and frequently cause significant mortality in CF patients. Understanding the mechanisms of persistence is important. Our work has demonstrated that the alginate regulatory system also significantly impacts the posttranscriptional regulator system RsmA/Y/Z. We demonstrate that AlgR directly activates rsmA expression, and this impacts the RsmA regulon. This leads to the possibility that the RsmA/Y/Z system plays a role in helping P. aeruginosa persist during chronic infection. In addition, this furthers our understanding of the reach of the alginate regulators AlgU and AlgR.
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Otton LM, da Silva Campos M, Meneghetti KL, Corção G. Influence of twitching and swarming motilities on biofilm formation in Pseudomonas strains. Arch Microbiol 2017; 199:677-682. [PMID: 28204863 DOI: 10.1007/s00203-017-1344-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 01/10/2017] [Accepted: 01/20/2017] [Indexed: 10/20/2022]
Abstract
The genus Pseudomonas mainly includes opportunistic pathogens that rely on type IV pili as an important virulence factor, which is associated with adherence and biofilm formation. Pseudomonas infections are well known to be persistent and resilient in nature largely because of the tendency of the species to form biofilms. This study aimed at analyzing environmental strains of Pseudomonas genus with respect to their ability to execute twitching and swarming motilities as well as with respect to their ability to form biofilms both in the presence as well as in the absence of furanone, a substance that has the potential to prevent the formation of biofilms. Strains of Pseudomonas aeruginosa and strains belonging to other species of the genus were analyzed. Twitching and swarming motility assays and biofilm-formation assays, both in the presence as well as in the absence of furanone, were performed. In twitching assay strains belonging to P. aeruginosa outperformed those belonging to other species. Interestingly, it was seen that the presence of furanone had a negative impact on formation of twitching and swarming motility zones. In the case of biofilm assays, it was observed that the presence of furanone resulted in an observable decrease in the degree of adhesion in 30% of the analyzed strains. Thus, from our results, it can be concluded that, as compared to other species, the strains belonging to P. aeruginosa exhibit a higher potential for twitching motility and similar performance in swarming motility and biofilm formation. It can also be concluded that furanone has the potential to interfere with both motilities as well as with biofilm formation.
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Affiliation(s)
- Letícia Muner Otton
- Department of Microbiology, Immunology and Parasitology, Institute of Basic Health Science, Universidade Federal do Rio Grande do Sul, Sarmento Leite, 500, Porto Alegre, Rio Grande do Sul, CEP 90050-170, Brazil
| | - Marina da Silva Campos
- Department of Microbiology, Immunology and Parasitology, Institute of Basic Health Science, Universidade Federal do Rio Grande do Sul, Sarmento Leite, 500, Porto Alegre, Rio Grande do Sul, CEP 90050-170, Brazil
| | - Karine Lena Meneghetti
- Department of Microbiology, Immunology and Parasitology, Institute of Basic Health Science, Universidade Federal do Rio Grande do Sul, Sarmento Leite, 500, Porto Alegre, Rio Grande do Sul, CEP 90050-170, Brazil
| | - Gertrudes Corção
- Department of Microbiology, Immunology and Parasitology, Institute of Basic Health Science, Universidade Federal do Rio Grande do Sul, Sarmento Leite, 500, Porto Alegre, Rio Grande do Sul, CEP 90050-170, Brazil.
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Scheie AA, Petersen FC. The Biofilm Concept: Consequences for Future Prophylaxis of Oral Diseases? ACTA ACUST UNITED AC 2016; 15:4-12. [PMID: 14761896 DOI: 10.1177/154411130401500102] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Biofilm control is fundamental to oral health. Existing oral prophylactic measures, however, are insufficient. The main reason is probably because the micro-organisms involved organize into complex biofilm communities with features that differ from those of planktonic cells. Micro-organisms have traditionally been studied in the planktonic state. Conclusions drawn from many of these studies, therefore, need to be revalidated. Recent global approaches to the study of microbial gene expression and regulation in non-oral micro-organisms have shed light on two-component and quorum-sensing systems for the transduction of stimuli that allow for coordinated gene expression. We suggest interference with two-component and quorum-sensing systems as potential novel strategies for the prevention of oral diseases through control of oral biofilms. Information is still lacking, however, on the genetic regulation of oral biofilm formation. A better understanding of these processes is of considerable importance.
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Affiliation(s)
- Anne Aamdal Scheie
- Dept. of Oral Biology, Faculty of Dentistry, University of Oslo, PB 1052 Blindern, 0316 Oslo, Norway
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27
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Desai SK, Kenney LJ. To ∼P or Not to ∼P? Non-canonical activation by two-component response regulators. Mol Microbiol 2016; 103:203-213. [PMID: 27656860 DOI: 10.1111/mmi.13532] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/15/2016] [Indexed: 12/30/2022]
Abstract
Bacteria sense and respond to their environment through the use of two-component regulatory systems. The ability to adapt to a wide range of environmental stresses is directly related to the number of two-component systems an organism possesses. Recent advances in this area have identified numerous variations on the archetype systems that employ a sensor kinase and a response regulator. It is now evident that many orphan regulators that lack cognate kinases do not rely on phosphorylation for activation and new roles for unphosphorylated response regulators have been identified. The significance of recent findings and suggestions for further research are discussed.
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Affiliation(s)
- Stuti K Desai
- Mechanobiology Institute, 5A Engineering Drive 1, National University of Singapore, Singapore, Singapore
| | - Linda J Kenney
- Mechanobiology Institute, 5A Engineering Drive 1, National University of Singapore, Singapore, Singapore.,Jesse Brown Veteran's Administration Medical Center, Chicago, IL, USA.,Department of Microbiology & Immunology, University of Illinois-Chicago, Chicago, IL, USA
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28
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The Pseudomonas aeruginosa PAO1 Two-Component Regulator CarSR Regulates Calcium Homeostasis and Calcium-Induced Virulence Factor Production through Its Regulatory Targets CarO and CarP. J Bacteriol 2016; 198:951-63. [PMID: 26755627 DOI: 10.1128/jb.00963-15] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 12/31/2015] [Indexed: 02/02/2023] Open
Abstract
UNLABELLED Pseudomonas aeruginosa is an opportunistic human pathogen that causes severe, life-threatening infections in patients with cystic fibrosis (CF), endocarditis, wounds, or artificial implants. During CF pulmonary infections, P. aeruginosa often encounters environments where the levels of calcium (Ca(2+)) are elevated. Previously, we showed that P. aeruginosa responds to externally added Ca(2+) through enhanced biofilm formation, increased production of several secreted virulence factors, and by developing a transient increase in the intracellular Ca(2+) level, followed by its removal to the basal submicromolar level. However, the molecular mechanisms responsible for regulating Ca(2+)-induced virulence factor production and Ca(2+) homeostasis are not known. Here, we characterized the genome-wide transcriptional response of P. aeruginosa to elevated [Ca(2+)] in both planktonic cultures and biofilms. Among the genes induced by CaCl2 in strain PAO1 was an operon containing the two-component regulator PA2656-PA2657 (here called carS and carR), while the closely related two-component regulators phoPQ and pmrAB were repressed by CaCl2 addition. To identify the regulatory targets of CarSR, we constructed a deletion mutant of carR and performed transcriptome analysis of the mutant strain at low and high [Ca(2+)]. Among the genes regulated by CarSR in response to CaCl2 are the predicted periplasmic OB-fold protein, PA0320 (here called carO), and the inner membrane-anchored five-bladed β-propeller protein, PA0327 (here called carP). Mutations in both carO and carP affected Ca(2+) homeostasis, reducing the ability of P. aeruginosa to export excess Ca(2+). In addition, a mutation in carP had a pleotropic effect in a Ca(2+)-dependent manner, altering swarming motility, pyocyanin production, and tobramycin sensitivity. Overall, the results indicate that the two-component system CarSR is responsible for sensing high levels of external Ca(2+) and responding through its regulatory targets that modulate Ca(2+) homeostasis, surface-associated motility, and the production of the virulence factor pyocyanin. IMPORTANCE During infectious disease, Pseudomonas aeruginosa encounters environments with high calcium (Ca(2+)) concentrations, yet the cells maintain intracellular Ca(2+) at levels that are orders of magnitude less than that of the external environment. In addition, Ca(2+) signals P. aeruginosa to induce the production of several virulence factors. Compared to eukaryotes, little is known about how bacteria maintain Ca(2+) homeostasis or how Ca(2+) acts as a signal. In this study, we identified a two-component regulatory system in P. aeruginosa PAO1, termed CarRS, that is induced at elevated Ca(2+) levels. CarRS modulates Ca(2+) signaling and Ca(2+) homeostasis through its regulatory targets, CarO and CarP. The results demonstrate that P. aeruginosa uses a two-component regulatory system to sense external Ca(2+) and relays that information for Ca(2+)-dependent cellular processes.
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29
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Kong W, Zhao J, Kang H, Zhu M, Zhou T, Deng X, Liang H. ChIP-seq reveals the global regulator AlgR mediating cyclic di-GMP synthesis in Pseudomonas aeruginosa. Nucleic Acids Res 2015. [PMID: 26206672 PMCID: PMC4787818 DOI: 10.1093/nar/gkv747] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
AlgR is a key transcriptional regulator required for the expression of multiple virulence factors, including type IV pili and alginate in Pseudomonas aeruginosa. However, the regulon and molecular regulatory mechanism of AlgR have yet to be fully elucidated. Here, among 157 loci that were identified by a ChIP-seq assay, we characterized a gene, mucR, which encodes an enzyme that synthesizes the intracellular second messenger cyclic diguanylate (c-di-GMP). A ΔalgR strain produced lesser biofilm than did the wild-type strain, which is consistent with a phenotype controlled by c-di-GMP. AlgR positively regulates mucR via direct binding to its promoter. A ΔalgRΔmucR double mutant produced lesser biofilm than did the single ΔalgR mutant, demonstrating that c-di-GMP is a positive regulator of biofilm formation. AlgR controls the levels of c-di-GMP synthesis via direct regulation of mucR. In addition, the cognate sensor of AlgR, FimS/AlgZ, also plays an important role in P. aeruginosa virulence. Taken together, this study provides new insights into the AlgR regulon and reveals the involvement of c-di-GMP in the mechanism underlying AlgR regulation.
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Affiliation(s)
- 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
| | - 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
| | - 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
| | - 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
| | - Tianhong Zhou
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, 23 Hongda Street, Tianjin 300457, China
| | - Xin Deng
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, 23 Hongda Street, Tianjin 300457, 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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Leighton TL, Buensuceso RNC, Howell PL, Burrows LL. Biogenesis of Pseudomonas aeruginosa type IV pili and regulation of their function. Environ Microbiol 2015; 17:4148-63. [PMID: 25808785 DOI: 10.1111/1462-2920.12849] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 03/13/2015] [Accepted: 03/14/2015] [Indexed: 12/27/2022]
Abstract
Type IV pili (T4P) are bacterial virulence factors involved in a wide variety of functions including deoxyribonucleic acid uptake, surface attachment, biofilm formation and twitching motility. While T4P are common surface appendages, the systems that assemble them and the regulation of their function differ between species. Pseudomonas aeruginosa, Neisseria spp. and Myxococcus xanthus are common model systems used to study T4P biology. This review focuses on recent advances in P. aeruginosa T4P structural biology, and the regulatory pathways controlling T4P biogenesis and function.
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Affiliation(s)
- Tiffany L Leighton
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
| | - Ryan N C Buensuceso
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
| | - P Lynne Howell
- Program in Molecular Structure & Function, The Hospital for Sick Children, Toronto, ON, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Lori L Burrows
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
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31
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Expression analysis of the Pseudomonas aeruginosa AlgZR two-component regulatory system. J Bacteriol 2014; 197:736-48. [PMID: 25488298 DOI: 10.1128/jb.02290-14] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa virulence components are subject to complex regulatory control primarily through two-component regulatory systems that allow for sensing and responding to environmental stimuli. In this study, the expression and regulation of the P. aeruginosa AlgZR two-component regulatory system were examined. Primer extension and S1 nuclease protection assays were used to identify two transcriptional initiation sites for algR within the algZ coding region, and two additional start sites were identified upstream of the algZ coding region. The two algR transcriptional start sites, RT1 and RT2, are directly regulated by AlgU, consistent with previous reports of increased algR expression in mucoid backgrounds, and RpoS additionally plays a role in algR transcription. The expression of the first algZ promoter, ZT1, is entirely dependent upon Vfr for expression, whereas Vfr, RpoS, or AlgU does not regulate the second algZ promoter, ZT2. Western blot, real-time quantitative PCR (RT-qPCR), and transcriptional fusion analyses show that algZR expression is Vfr dependent. The algZ and algR genes also are cotranscribed in both nonmucoid and mucoid backgrounds. Furthermore, algZR was found to be cotranscribed with hemCD by RT-PCR. RT-qPCR confirmed that hemC transcription in the PAO1 ΔalgZ mutant was 40% of the level of the wild-type strain. Taken together, these results indicate that algZR transcription involves multiple factors at multiple start sites that control individual gene expression as well as coexpression of this two-component system with heme biosynthetic genes.
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Kulkarni HM, Jagannadham MV. Biogenesis and multifaceted roles of outer membrane vesicles from Gram-negative bacteria. Microbiology (Reading) 2014; 160:2109-2121. [DOI: 10.1099/mic.0.079400-0] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Outer membrane vesicles (OMVs) released from Gram-negative bacteria consist of lipids, proteins, lipopolysaccharides and other molecules. OMVs are associated with several biological functions such as horizontal gene transfer, intracellular and intercellular communication, transfer of contents to host cells, and eliciting an immune response in host cells. Although hypotheses have been made concerning the mechanism of biogenesis of these vesicles, research on OMV formation is far from complete. The roles of outer membrane components, bacterial quorum sensing molecules and some specific proteins in OMV biogenesis have been studied. This review discusses the different models that have been proposed for OMV biogenesis, along with details of the biological functions of OMVs and the likely scope of future research.
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Affiliation(s)
- Heramb M. Kulkarni
- CSIR – Centre for Cellular and Molecular Biology, Tarnaka, Hyderabad-500007, India
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33
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Sousa AM, Pereira MO. Pseudomonas aeruginosa Diversification during Infection Development in Cystic Fibrosis Lungs-A Review. Pathogens 2014; 3:680-703. [PMID: 25438018 PMCID: PMC4243435 DOI: 10.3390/pathogens3030680] [Citation(s) in RCA: 169] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 08/11/2014] [Accepted: 08/12/2014] [Indexed: 01/14/2023] Open
Abstract
Pseudomonas aeruginosa is the most prevalent pathogen of cystic fibrosis (CF) lung disease. Its long persistence in CF airways is associated with sophisticated mechanisms of adaptation, including biofilm formation, resistance to antibiotics, hypermutability and customized pathogenicity in which virulence factors are expressed according the infection stage. CF adaptation is triggered by high selective pressure of inflamed CF lungs and by antibiotic treatments. Bacteria undergo genetic, phenotypic, and physiological variations that are fastened by the repeating interplay of mutation and selection. During CF infection development, P. aeruginosa gradually shifts from an acute virulent pathogen of early infection to a host-adapted pathogen of chronic infection. This paper reviews the most common changes undergone by P. aeruginosa at each stage of infection development in CF lungs. The comprehensive understanding of the adaptation process of P. aeruginosa may help to design more effective antimicrobial treatments and to identify new targets for future drugs to prevent the progression of infection to chronic stages.
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Affiliation(s)
- Ana Margarida Sousa
- CEB-Centre of Biological Engineering, LIBRO-Laboratório de Investigação em Biofilmes Rosário Oliveira, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
| | - Maria Olívia Pereira
- CEB-Centre of Biological Engineering, LIBRO-Laboratório de Investigação em Biofilmes Rosário Oliveira, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
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Okkotsu Y, Little AS, Schurr MJ. The Pseudomonas aeruginosa AlgZR two-component system coordinates multiple phenotypes. Front Cell Infect Microbiol 2014; 4:82. [PMID: 24999454 PMCID: PMC4064291 DOI: 10.3389/fcimb.2014.00082] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 06/02/2014] [Indexed: 01/28/2023] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that causes a multitude of infections. These infections can occur at almost any site in the body and are usually associated with a breach of the innate immune system. One of the prominent sites where P. aeruginosa causes chronic infections is within the lungs of cystic fibrosis patients. P. aeruginosa uses two-component systems that sense environmental changes to differentially express virulence factors that cause both acute and chronic infections. The P. aeruginosa AlgZR two component system is one of its global regulatory systems that affects the organism's fitness in a broad manner. This two-component system is absolutely required for two P. aeruginosa phenotypes: twitching motility and alginate production, indicating its importance in both chronic and acute infections. Additionally, global transcriptome analyses indicate that it regulates the expression of many different genes, including those associated with quorum sensing, type IV pili, type III secretion system, anaerobic metabolism, cyanide and rhamnolipid production. This review examines the complex AlgZR regulatory network, what is known about the structure and function of each protein, and how it relates to the organism's ability to cause infections.
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Affiliation(s)
- Yuta Okkotsu
- Department of Microbiology, University of Colorado School of Medicine Aurora, CO, USA
| | - Alexander S Little
- Department of Microbiology, University of Colorado School of Medicine Aurora, CO, USA
| | - Michael J Schurr
- Department of Microbiology, University of Colorado School of Medicine Aurora, CO, USA
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Pseudomonas aeruginosa AlgR phosphorylation modulates rhamnolipid production and motility. J Bacteriol 2013; 195:5499-515. [PMID: 24097945 DOI: 10.1128/jb.00726-13] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AlgR is a key Pseudomonas aeruginosa transcriptional response regulator required for virulence. AlgR activates alginate production and twitching motility but represses the Rhl quorum-sensing (QS) system, including rhamnolipid production. The role of AlgR phosphorylation is enigmatic, since phosphorylated AlgR (AlgR-P) is required for twitching motility through the fimU promoter but is not required for the activation of alginate production. In order to examine the role of AlgR phosphorylation in vivo, a PAO1 algRD54E strain (with algR encoding a D-to-E change at position 54), which constitutively activates fimU transcription and exhibits twitching motility, was created. A corresponding PAO1 algRD54N strain (with algR encoding a D-to-N change at position 54) that does not activate fimU or twitching motility was compared to PAO1, PAO1 algRD54E, PAO1 ΔalgZ (deletion of the algZ [fimS] gene, encoding a putative histidine kinase), and PAO1 ΔalgR for swarming motility, rhamnolipid production, and rhlA transcription. PAO1 and PAO1 algRD54E produced approximately 2-fold-higher levels of rhamnolipids than PAO1 algRD54N and PAO1 ΔalgZ, thereby indicating that phosphorylated AlgR is required for normal rhamnolipid production. Examination of purified AlgR, AlgR-P, AlgR D54N, and AlgR D54E showed that AlgR-P and AlgR D54E bound preferentially to the fimU and rhlA promoters. Additionally, AlgR-P bound specifically to two sites within the rhlA promoter that were not bound by unphosphorylated AlgR. Taken together, these results indicate that phosphorylated AlgR-P has increased affinity for the rhlA promoter and is required for the coordinate activation of twitching motility, rhamnolipid production, and swarming motility in P. aeruginosa.
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Wang S, Parsek MR, Wozniak DJ, Ma LZ. A spider web strategy of type IV pili-mediated migration to build a fibre-like Psl polysaccharide matrix in Pseudomonas aeruginosa biofilms. Environ Microbiol 2013; 15:2238-53. [PMID: 23425591 DOI: 10.1111/1462-2920.12095] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Accepted: 01/21/2013] [Indexed: 12/19/2022]
Abstract
Bacterial motilities participate in biofilm development. However, it is unknown how/if bacterial motility affects formation of the biofilm matrix. Psl polysaccharide is a key biofilm matrix component of Pseudomonas aeruginosa. Here we report that type IV pili (T4P)-mediated bacterial migration leads to the formation of a fibre-like Psl matrix. Deletion of T4P in wild type and flagella-deficient strains results in loss of the Psl-fibres and reduction of biofilm biomass in flow cell biofilms as well as pellicles at air-liquid interface. Bacteria lacking T4P-driven twitching motility including those that still express surface T4P are unable to form the Psl-fibres. Formation of a Psl-fibre matrix is critical for efficient biofilm formation, yet does not require flagella and polysaccharide Pel or alginate. The Psl-fibres are likely formed by Psl released from bacteria during T4P-mediated migration, a strategy similar to spider web formation. Starvation can couple Psl release and T4P-driven twitching motility. Furthermore, a radial-pattern Psl-fibre matrix is present in the middle of biofilms, a nutrient-deprived region. These imply a plausible model for how bacteria respond to nutrient-limited local environment to build a polysaccharide-fibre matrix by T4P-dependent bacterial migration strategy. This strategy may have general significance for bacterial survival in natural and clinical settings.
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Affiliation(s)
- Shiwei Wang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
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Mucin biopolymers prevent bacterial aggregation by retaining cells in the free-swimming state. Curr Biol 2012; 22:2325-30. [PMID: 23142047 DOI: 10.1016/j.cub.2012.10.028] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Revised: 09/18/2012] [Accepted: 10/16/2012] [Indexed: 01/11/2023]
Abstract
Many species of bacteria form surface-attached communities known as biofilms. Surrounded in secreted polymers, these aggregates are difficult both to prevent and eradicate, posing problems for medicine and industry. Humans play host to hundreds of trillions of microbes that live adjacent to our epithelia, and we are typically able to prevent harmful colonization. Mucus, the hydrogel overlying all wet epithelia in the body, can prevent bacterial contact with the underlying tissue. The digestive tract, for example, is lined by a firmly adherent mucus layer that is typically devoid of bacteria, followed by a second, loosely adherent layer that contains numerous bacteria. Here, we investigate the role of mucus as a principle arena for host-microbe interactions. Using defined in vitro assays, we found that mucin biopolymers, the main functional constituents of mucus, promote the motility of planktonic bacteria and prevent their adhesion to underlying surfaces. The deletion of motility genes, however, allows Pseudomonas aeruginosa to overcome the dispersive effects of mucus and form suspended antibiotic-resistant flocs, which mirror the clustered morphology of immotile natural isolates found in the cystic fibrosis lung mucus. Mucus may offer new strategies to target bacterial virulence, such as the design of antibiofilm coatings for implants.
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Sticky situations: key components that control bacterial surface attachment. J Bacteriol 2012; 194:2413-25. [PMID: 22389478 DOI: 10.1128/jb.00003-12] [Citation(s) in RCA: 216] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The formation of bacterial biofilms is initiated by cells transitioning from the free-swimming mode of growth to a surface. This review is aimed at highlighting the common themes that have emerged in recent research regarding the key components, signals, and cues that aid in the transition and those involved in establishing a more permanent surface association during initial attachment.
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Yan Q, Wang N. High-throughput screening and analysis of genes of Xanthomonas citri subsp. citri involved in citrus canker symptom development. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:69-84. [PMID: 21899385 DOI: 10.1094/mpmi-05-11-0121] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Citrus canker is caused by Xanthomonas citri subsp. citri and is one of the most devastating diseases on citrus plants. To investigate the virulence mechanism of this pathogen, a mutant library of strain 306 containing approximately 22,000 mutants was screened for virulence-deficient mutants in grapefruit (Citrus paradise). Eighty-two genes were identified that contribute to citrus canker symptom development caused by X. citri subsp. citri. Among the 82 identified genes, 23 genes were classified as essential genes, as mutation of these genes caused severe reduction of bacterial growth in M9 medium. The remaining 59 genes were classified as putative virulence-related genes that include 32 previously reported virulence-related genes and 27 novel genes. The 32 known virulence-related genes include genes that are involved in the type III secretion system (T3SS) and T3SS effectors, the quorum-sensing system, extracellular polysaccharide and lipopolysaccharide synthesis, and general metabolic pathways. The contribution to pathogenesis by nine genes (pthA4, trpG, trpC, purD, hrpM, peh-1, XAC1230, XAC1548, and XAC3049) was confirmed by complementation assays. We further validated the mutated genes and their phenotypes by analyzing the EZ-Tn5 insertion copy number using Southern blot analysis. In conclusion, we have significantly advanced our understanding of the putative genetic determinants of the virulence mechanism of X. citri subsp. citri by identifying 59 putative virulence-related genes, including 27 novel genes.
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Affiliation(s)
- Qing Yan
- Department of Microbiology and Cell Science, University of Florida, Lake Alfred, FL, USA
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Koh AY, Mikkelsen PJ, Smith RS, Coggshall KT, Kamei A, Givskov M, Lory S, Pier GB. Utility of in vivo transcription profiling for identifying Pseudomonas aeruginosa genes needed for gastrointestinal colonization and dissemination. PLoS One 2010; 5:e15131. [PMID: 21170272 PMCID: PMC3000825 DOI: 10.1371/journal.pone.0015131] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2010] [Accepted: 10/25/2010] [Indexed: 12/01/2022] Open
Abstract
Microarray analysis of Pseudomonas aeruginosa mRNA transcripts expressed in vivo during animal infection has not been previously used to investigate potential virulence factors needed in this setting. We compared mRNA expression in bacterial cells recovered from the gastrointestinal (GI) tracts of P. aeruginosa-colonized mice to that of P. aeruginosa in the drinking water used to colonize the mice. Genes associated with biofilm formation and type III secretion (T3SS) had markedly increased expression in the GI tract. A non-redundant transposon library in P. aeruginosa strain PA14 was used to test mutants in genes identified as having increased transcription during in vivo colonization. All of the Tn-library mutants in biofilm-associated genes had an attenuated ability to form biofilms in vitro, but there were no significant differences in GI colonization and dissemination between these mutants and WT P. aeruginosa PA14. To evaluate T3SS factors, we tested GI colonization and neutropenia-induced dissemination of both deletional (PAO1 and PAK) and insertional (PA14) mutants in four genes in the P. aeruginosa T3SS, exoS or exoU, exoT, and popB. There were no significant differences in GI colonization among these mutant strains and their WT counterparts, whereas rates of survival following dissemination were significantly decreased in mice infected by the T3SS mutant strains. However, there was a variable, strain-dependent effect on overall survival between parental and T3SS mutants. Thus, increased transcription of genes during in vivo murine GI colonization is not predictive of an essential role for the gene product in either colonization or overall survival following induction of neutropenia.
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Affiliation(s)
- Andrew Y Koh
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America.
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Regulation of virulence gene transcripts by the Francisella novicida orphan response regulator PmrA: role of phosphorylation and evidence of MglA/SspA interaction. Infect Immun 2010; 78:2189-98. [PMID: 20231408 DOI: 10.1128/iai.00021-10] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Francisella tularensis subsp. tularensis is the etiologic agent of tularemia and has been designated a category A biothreat agent by the CDC. Tularemia is characterized by replication and dissemination within host phagocytes. Intramacrophage growth is dependent upon the regulation of Francisella pathogenicity island (FPI) virulence genes, which is poorly understood. Two-component regulatory systems (TCS) are widely employed by Gram-negative bacteria to monitor and respond to environmental signals. Virulent strains of F. tularensis subsp. tularensis are devoid of classical, tandemly arranged TCS genes, but orphaned members, such as that encoding the response regulator PmrA, have been identified. In the F. novicida model system, previous work has shown that a pmrA mutant shows decreased expression of FPI genes, is deficient for intramacrophage growth, and is avirulent in the mouse model. Here, we determine that phosphorylation aids PmrA binding to regulated promoters pmrA and the FPI-encoded pdpD, and KdpD is the histidine kinase primarily responsible for phosphorylation of PmrA at the aspartic acid at position 51 (D51). A strain expressing PmrA D51A retains some DNA binding but exhibits reduced expression of the PmrA regulon, is deficient for intramacrophage replication, and is attenuated in the mouse model. With regard to virulence gene induction, PmrA coprecipitates with the FPI transcription factors MglA and SspA, which bind RNA polymerase. Together, these data suggest a model of Francisella gene regulation that includes a TCS consisting of KdpD and PmrA. Once phosphorylated, PmrA binds to regulated gene promoters recruiting free or RNA polymerase-bound MglA and SspA to initiate FPI gene transcription.
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Müsken M, Di Fiore S, Dötsch A, Fischer R, Häussler S. Genetic determinants of Pseudomonas aeruginosa biofilm establishment. Microbiology (Reading) 2010; 156:431-441. [DOI: 10.1099/mic.0.033290-0] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The establishment of bacterial biofilms on surfaces is a complex process that requires various factors for each consecutive developmental step. Here we report the screening of the comprehensive Harvard Pseudomonas aeruginosa PA14 mutant library for mutants exhibiting an altered biofilm phenotype. We analysed the capability of all mutants to form biofilms at the bottom of a 96-well plate by the use of an automated confocal laser-scanning microscope and found 394 and 285 genetic determinants of reduced and enhanced biofilm production, respectively. Overall, 67 % of the identified mutants were affected within genes encoding hypothetical proteins, indicating that novel developmental pathways are likely to be dissected in the future. Nevertheless, a common theme that emerged from the analysis of the genes with a predicted function is that the establishment of a biofilm requires regulatory components that are involved in survival under microaerophilic growth conditions, arginine metabolism, alkyl-quinolone signalling, pH homeostasis and the DNA repair system.
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Affiliation(s)
- Mathias Müsken
- Chronic Pseudomonas Infection Research Group, Helmholtz Center for Infection Research, Inhoffenstrasse 7, D-38124 Braunschweig, Germany
| | - Stefano Di Fiore
- Fraunhofer Institute for Molecular Biology and Applied Ecology, Forckenbeck Str. 6, D-52704 Aachen, Germany
- Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, D-52704 Aachen, Germany
| | - Andreas Dötsch
- Chronic Pseudomonas Infection Research Group, Helmholtz Center for Infection Research, Inhoffenstrasse 7, D-38124 Braunschweig, Germany
| | - Rainer Fischer
- Fraunhofer Institute for Molecular Biology and Applied Ecology, Forckenbeck Str. 6, D-52704 Aachen, Germany
| | - Susanne Häussler
- Twincore, Center for Experimental and Clinical Infection Research, a joint venture of the Helmholtz Center for Infection Research and the Medical School Hannover, Feodor Lynen Strasse 7, D-30265 Hannover, Germany
- Chronic Pseudomonas Infection Research Group, Helmholtz Center for Infection Research, Inhoffenstrasse 7, D-38124 Braunschweig, Germany
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Expression of Kingella kingae type IV pili is regulated by sigma54, PilS, and PilR. J Bacteriol 2009; 191:4976-86. [PMID: 19465661 DOI: 10.1128/jb.00123-09] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Kingella kingae is a member of the Neisseriaceae and is being recognized increasingly as an important cause of serious disease in children. Recent work has demonstrated that K. kingae expresses type IV pili that mediate adherence to respiratory epithelial and synovial cells and are selected against during invasive disease. In the current study, we examined the genome of K. kingae strain 269-492 and identified homologs of the rpoN and the pilS and pilR genes that are essential for pilus expression in Pseudomonas aeruginosa but not in the pathogenic Neisseria species. The disruption of either rpoN or pilR in K. kingae resulted in a marked reduction in the level of transcript for the major pilus subunit (pilA1) and eliminated piliation. In contrast, the disruption of pilS resulted in only partial reduction in the level of pilA1 transcript and a partial decrease in piliation. Furthermore, the disruption of pilS in colony variants with high-density piliation resulted in variants with low-density piliation. Mutations in the promoter region of pilA1 and gel shift analysis demonstrated that both sigma(54) and PilR act directly at the pilA1 promoter, with PilR binding to two repetitive elements. These data suggest that the regulation of K. kingae type IV pilus expression is complex and multilayered, influenced by both the genetic state and environmental cues.
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Abstract
In nature, the bulk of bacterial biomass is believed to exist as an adherent community of cells called a biofilm. Pseudomonas aeruginosa has become a model organism for studying this mode of growth. Over the past decade, significant strides have been made towards understanding biofilm development in P. aeruginosa and we now have a clearer picture of the mechanisms involved. Available evidence suggests that construction of these sessile communities proceeds by many different pathways, rather than a specific programme of biofilm development. A cell-to-cell communication mechanism known as quorum sensing (QS) has been found to play a role in P. aeruginosa biofilm formation. Because both QS and biofilms are impacted by the surrounding environment, understanding the full involvement of cell-to-cell signalling in establishing these complex communities represents a challenge. Nevertheless, under set conditions, several links between QS and biofilm formation have been recognized, which is the focus of this review. A role for antibiotics as alternative QS signalling molecules influencing biofilm development is also discussed.
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Affiliation(s)
- T R de Kievit
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada.
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Pseudomonas aeruginosa AlgR controls cyanide production in an AlgZ-dependent manner. J Bacteriol 2009; 191:2993-3002. [PMID: 19270096 DOI: 10.1128/jb.01156-08] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that causes chronic infections in individuals suffering from the genetic disorder cystic fibrosis. In P. aeruginosa, the transcriptional regulator AlgR controls a variety of virulence factors, including alginate production, twitching motility, biofilm formation, quorum sensing, and hydrogen cyanide (HCN) production. In this study, the regulation of HCN production was examined. Strains lacking AlgR or the putative AlgR sensor AlgZ produced significantly less HCN than did a nonmucoid isogenic parent. In contrast, algR and algZ mutants showed increased HCN production in an alginate-producing (mucoid) background. HCN production was optimal in a 5% O2 environment. In addition, cyanide production was elevated in bacteria grown on an agar surface compared to bacteria grown in planktonic culture. A conserved AlgR phosphorylation site (aspartate at amino acid position 54), which is required for surface-dependent twitching motility but not alginate production, was found to be critical for cyanide production. Nuclease protection mapping of the hcnA promoter identified a new transcriptional start site required for HCN production. A subset of clinical isolates that lack this start site produced small amounts of cyanide. Taken together, these data show that the P. aeruginosa hcnA promoter contains three transcriptional start sites and that HCN production is regulated by AlgZ and AlgR and is maximal under microaerobic conditions when the organism is surface attached.
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Gooderham WJ, Hancock REW. Regulation of virulence and antibiotic resistance by two-component regulatory systems inPseudomonas aeruginosa. FEMS Microbiol Rev 2009; 33:279-94. [DOI: 10.1111/j.1574-6976.2008.00135.x] [Citation(s) in RCA: 238] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Vitale E, Milani A, Renzi F, Galli E, Rescalli E, de Lorenzo V, Bertoni G. Transcriptional wiring of the TOL plasmid regulatory network to its host involves the submission of the sigma54-promoter Pu to the response regulator PprA. Mol Microbiol 2009; 69:698-713. [PMID: 19138193 DOI: 10.1111/j.1365-2958.2008.06321.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Implantation of the regulatory circuit of the degradation pathway of TOL plasmid pWW0 in the native transcriptional network of the host Pseudomonas putida involves interplay between plasmid- and chromosome-encoded factors. We have employed a reverse genetics approach to investigate such a molecular wiring by identifying host proteins that form stable complexes with Pu, the sigma(54)-dependent promoter of the upper TOL operon of pWW0. This approach revealed that the Pu upstream activating sequences (UAS), the target sites of the cognate activator XylR, form a specific complex with a host protein which, following DNA affinity purification and mass spectrometry analysis, was identified as the LytTR-type two-component response regulator PprA. Directed inactivation of pprA resulted in the upregulation of the Pu promoter in vivo, while expression of the same gene from a plasmid vector strongly repressed Pu activity. Such a downregulation of Pu by PprA could be faithfully reproduced both in vitro with purified components and in an in vivo reporter system assembled in Escherichia coli. The overlap of the PprA and XylR binding sites suggested that the basis for the inhibitory effect on Pu was a mutual exclusion mechanism between the two proteins to bind the UAS. We argue that the binding of the response regulator PprA to Pu (a case without precedents in sigma(54)-dependent transcription) helps to anchor the TOL regulatory subnetwork to the wider context of the host transcriptome, thereby allowing the entry of physiological signals that modulate the outcome of promoter activity.
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Affiliation(s)
- Elena Vitale
- Department of Biomolecular Sciences and Biotechnology, University of Milan, Milan, Italy
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Extracellular DNA chelates cations and induces antibiotic resistance in Pseudomonas aeruginosa biofilms. PLoS Pathog 2008; 4:e1000213. [PMID: 19023416 PMCID: PMC2581603 DOI: 10.1371/journal.ppat.1000213] [Citation(s) in RCA: 439] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2008] [Accepted: 10/21/2008] [Indexed: 01/18/2023] Open
Abstract
Biofilms are surface-adhered bacterial communities encased in an extracellular matrix composed of DNA, bacterial polysaccharides and proteins, which are up to 1000-fold more antibiotic resistant than planktonic cultures. To date, extracellular DNA has been shown to function as a structural support to maintain Pseudomonas aeruginosa biofilm architecture. Here we show that DNA is a multifaceted component of P. aeruginosa biofilms. At physiologically relevant concentrations, extracellular DNA has antimicrobial activity, causing cell lysis by chelating cations that stabilize lipopolysaccharide (LPS) and the outer membrane (OM). DNA-mediated killing occurred within minutes, as a result of perturbation of both the outer and inner membrane (IM) and the release of cytoplasmic contents, including genomic DNA. Sub-inhibitory concentrations of DNA created a cation-limited environment that resulted in induction of the PhoPQ- and PmrAB-regulated cationic antimicrobial peptide resistance operon PA3552–PA3559 in P. aeruginosa. Furthermore, DNA-induced expression of this operon resulted in up to 2560-fold increased resistance to cationic antimicrobial peptides and 640-fold increased resistance to aminoglycosides, but had no effect on β-lactam and fluoroquinolone resistance. Thus, the presence of extracellular DNA in the biofilm matrix contributes to cation gradients, genomic DNA release and inducible antibiotic resistance. DNA-rich environments, including biofilms and other infection sites like the CF lung, are likely the in vivo environments where extracellular pathogens such as P. aeruginosa encounter cation limitation. Pseudomonas aeruginosa is an opportunistic pathogen, which causes a variety of serious infections in immunocompromised patients and cystic fibrosis (CF) sufferers. The biofilm-forming ability of P. aeruginosa is thought to contribute to chronic P. aeruginosa infection of the CF lung. Biofilms are dense communities of bacteria, encased in an extracellular matrix, that are practically impossible to eradicate using available antimicrobial therapies. Understanding the mechanisms by which biofilm bacteria develop resistance to antibiotics is paramount to expanding the treatment options available to patients with chronic biofilm infections. In this study we have identified a novel mechanism of biofilm-specific antibiotic resistance. Extracellular DNA, a known component of biofilms, was found to induce antibiotic resistance. This previously unidentified function of DNA was due to its ability to bind and sequester cations, including magnesium, from the surrounding environment. This environmental cue was then detected by P. aeruginosa leading to induction of genes involved in modification of the cell surface component, lipopolysaccharide (LPS), resulting in physical alterations in the bacterial outer membrane (OM). These results demonstrate a novel function for DNA in biofilms and identify cation chelation by DNA as a previously unrecognized mechanism, which can explain the increased resistance of biofilms to antimicrobial agents.
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Prophylactic and therapeutic efficacy of a fully human immunoglobulin G1 monoclonal antibody to Pseudomonas aeruginosa alginate in murine keratitis infection. Infect Immun 2008; 76:4720-5. [PMID: 18644881 DOI: 10.1128/iai.00496-08] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Treatment of ulcerative keratitis due to Pseudomonas aeruginosa is difficult, time-consuming, and uncomfortable owing to the need for the frequent application of antibiotic drops to the infected corneal surface. We examined here whether a fully human immunoglobulin G1 monoclonal antibody (MAb) specific to the conserved alginate surface polysaccharide of P. aeruginosa could mediate protective immunity against typically nonmucoid strains isolated from human cases of keratitis. MAb F429 effectively opsonized alginate-positive, but not alginate-negative, nonmucoid strains in conjunction with phagocytes and complement. Prophylactic administration of MAb F429 18 h prior to infection with two clinical isolates significantly reduced bacterial levels in the eye and the associated corneal pathology. Along similar lines, systemic intraperitoneal injection, as well as topical application of the MAb onto the infected eye, starting 8 h postinfection in both experimental protocols resulted in significant reductions in bacteria in the eye, as well as minimizing pathological damage to the cornea. These findings indicate that MAb F429 could be useful as an additional therapeutic component for the treatment of P. aeruginosa keratitis.
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