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Sharma DK, Rajpurohit YS. Multitasking functions of bacterial extracellular DNA in biofilms. J Bacteriol 2024; 206:e0000624. [PMID: 38445859 PMCID: PMC11025335 DOI: 10.1128/jb.00006-24] [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] [Indexed: 03/07/2024] Open
Abstract
Bacterial biofilms are intricate ecosystems of microbial communities that adhere to various surfaces and are enveloped by an extracellular matrix composed of polymeric substances. Within the context of bacterial biofilms, extracellular DNA (eDNA) originates from cell lysis or is actively secreted, where it exerts a significant influence on the formation, stability, and resistance of biofilms to environmental stressors. The exploration of eDNA within bacterial biofilms holds paramount importance in research, with far-reaching implications for both human health and the environment. An enhanced understanding of the functions of eDNA in biofilm formation and antibiotic resistance could inspire the development of strategies to combat biofilm-related infections and improve the management of antibiotic resistance. This comprehensive review encapsulates the latest discoveries concerning eDNA, encompassing its origins, functions within bacterial biofilms, and significance in bacterial pathogenesis.
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Affiliation(s)
- Dhirendra Kumar Sharma
- Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, India
- Schools of Life Sciences, Homi Bhabha National Institute (DAE—Deemed University), Mumbai, India
| | - Yogendra Singh Rajpurohit
- Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, India
- Schools of Life Sciences, Homi Bhabha National Institute (DAE—Deemed University), Mumbai, India
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2
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Grant NA, Donkor GY, Sontz JT, Soto W, Waters CM. Deployment of a Vibrio cholerae ordered transposon mutant library in a quorum-competent genetic background. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.10.31.564941. [PMID: 37961142 PMCID: PMC10634969 DOI: 10.1101/2023.10.31.564941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Vibrio cholerae, the causative agent of cholera, has sparked seven pandemics in recent centuries, with the current one being the most prolonged. V. cholerae's pathogenesis hinges on its ability to switch between low and high cell density gene regulatory states, enabling transmission between host and the environment. Previously, a transposon mutant library for V. cholerae was created to support investigations aimed toward uncovering the genetic determinants of its pathogenesis. However, subsequent sequencing uncovered a mutation in the gene luxO of the parent strain, rendering mutants unable to exhibit high cell density behaviors. In this study, we used chitin-independent natural transformation to move transposon insertions from these low cell density mutants into a wildtype genomic background. Library transfer was aided by a novel gDNA extraction we developed using thymol, which also showed high lysis-specificity for Vibrio. The resulting Grant Library comprises 3,102 unique transposon mutants, covering 79.8% of V. cholerae's open reading frames. Whole genome sequencing of randomly selected mutants demonstrates 100% precision in transposon transfer to cognate genomic positions of the recipient strain. Notably, in no instance did the luxO mutation transfer into the wildtype background. Our research uncovered density-dependent epistasis in growth on inosine, an immunomodulatory metabolite secreted by gut bacteria that is implicated in enhancing gut barrier functions. Additionally, Grant Library mutants retain the plasmid that enables rapid, scarless genomic editing. In summary, the Grant Library reintroduces organismal relevant genetic contexts absent in the low cell density locked library equivalent.
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Affiliation(s)
- Nkrumah A. Grant
- Department of Microbiology, University of Illinois Urbana-Champaign, Urbana, IL
- Department of Microbiology, Genetics, and Immunology, Michigan State University, East Lansing MI
- BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, MI
| | | | - Jordan T. Sontz
- MSU College of Osteopathic Medicine, Michigan State University, East Lansing, MI
| | - William Soto
- Department of Biology, College of William and Mary, Williamsburg, VA
| | - Christopher M. Waters
- Department of Microbiology, Genetics, and Immunology, Michigan State University, East Lansing MI
- BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, MI
- MSU College of Osteopathic Medicine, Michigan State University, East Lansing, MI
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Tang X, Yang Z, Dai K, Liu G, Chang YF, Tang X, Wang K, Zhang Y, Hu B, Cao S, Huang X, Yan Q, Wu R, Zhao Q, Du S, Lang Y, Han X, Huang Y, Wen X, Wen Y. The molecular diversity of transcriptional factor TfoX is a determinant in natural transformation in Glaesserella parasuis. Front Microbiol 2022; 13:948633. [PMID: 35966685 PMCID: PMC9372613 DOI: 10.3389/fmicb.2022.948633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 07/12/2022] [Indexed: 11/13/2022] Open
Abstract
Natural transformation is a mechanism by which a particular bacterial species takes up foreign DNA and integrates it into its genome. The swine pathogen Glaesserella parasuis (G. parasuis) is a naturally transformable bacterium. The regulation of competence, however, is not fully understood. In this study, the natural transformability of 99 strains was investigated. Only 44% of the strains were transformable under laboratory conditions. Through a high-resolution melting curve and phylogenetic analysis, we found that genetic differences in the core regulator of natural transformation, the tfoX gene, leads to two distinct natural transformation phenotypes. In the absence of the tfoX gene, the highly transformable strain SC1401 lost its natural transformability. In addition, when the SC1401 tfoX gene was replaced by the tfoX of SH0165, which has no natural transformability, competence was also lost. These results suggest that TfoX is a core regulator of natural transformation in G. parasuis, and that differences in tfoX can be used as a molecular indicator of natural transformability. Transcriptomic and proteomic analyses of the SC1401 wildtype strain, and a tfoX gene deletion strain showed that differential gene expression and protein synthesis is mainly centered on pathways related to glucose metabolism. The results suggest that tfoX may mediate natural transformation by regulating the metabolism of carbon sources. Our study provides evidence that tfoX plays an important role in the natural transformation of G. parasuis.
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Affiliation(s)
- Xiaoyu Tang
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Zhen Yang
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Ke Dai
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Geyan Liu
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Yung-Fu Chang
- Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, United States
| | - Xinwei Tang
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Kang Wang
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Yiwen Zhang
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Bangdi Hu
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Sanjie Cao
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Xiaobo Huang
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Qigui Yan
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Rui Wu
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Qin Zhao
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Senyan Du
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Yifei Lang
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Xinfeng Han
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Yong Huang
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Xintian Wen
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Yiping Wen
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
- *Correspondence: Yiping Wen,
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Hu Y, Zheng J, Zhang J. Natural Transformation in Acinetobacter baumannii W068: A Genetic Analysis Reveals the Involvements of the CRP, XcpV, XcpW, TsaP, and TonB2. Front Microbiol 2022; 12:738034. [PMID: 35126321 PMCID: PMC8811193 DOI: 10.3389/fmicb.2021.738034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 12/14/2021] [Indexed: 01/25/2023] Open
Abstract
Acinetobacter baumannii is a serious threat to public health, and there is increasing attention to the development of antibiotic resistance in this bacterium. Natural transformation is a major horizontal gene transfer mechanism that can lead to antibiotic resistance. To better understand the mechanism of natural transformation in A. baumannii, we selected a clinical isolate that was transformable but had no visible extracellular type IV pili (T4P) filaments and then examined the effects of multiple single-gene knockouts on natural plasmid transformation. Among 33 candidate genes, 28 knockout mutants had severely or completely impaired transformability. Some of these genes had established roles in T4P biogenesis; DNA transfer across the outer membrane, periplasm, or inner membrane; and protection of intracellular single-stranded DNA (ssDNA). Other genes had no previously reported roles in natural transformation of A. baumannii, including competence activator cAMP receptor protein (CRP), a periplasmic protein that may function in T4P assembly (TonB2), a T4P secretin-associated protein (TsaP), and two type II secretion system (T2SS) minor pseudopilus assembly prime complex competent proteins (XcpV and XcpW). The deletion of the T2SS assembly platform protein X had no effect on transformation, and the minor pseudopilins were capable of initiating major pilin assembly. Thus, we speculate that XcpV and XcpW may function in DNA uptake with major pilin assembly, a non-T2SS-dependent mechanism and that a competence pseudopilus similar to T4P constituted the central part of the DNA uptake complex. These results may help guide future research on the alarming increase of antibiotic resistance in this pathogen.
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Affiliation(s)
- Yuan Hu
- State Key Laboratory of Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Junjie Zheng
- The Fifth Medical Center of Chinese PLA General Hospital, Beijing, China
| | - Jianzhong Zhang
- State Key Laboratory of Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
- *Correspondence: Jianzhong Zhang,
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Natural Transformation in a Classical-Biotype Vibrio cholerae Strain. Appl Environ Microbiol 2021; 87:AEM.00060-21. [PMID: 33712424 DOI: 10.1128/aem.00060-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 03/04/2021] [Indexed: 11/20/2022] Open
Abstract
Vibrio cholerae causes the gastrointestinal illness cholera, which spreads throughout the globe in large pandemics. The current pandemic is caused by O1 El Tor biotype strains, whereas previous pandemics were caused by O1 classical biotype strains. El Tor V. cholerae is noted for its ability to acquire exogenous DNA through chitin-induced natural transformation, which has been exploited for genetic manipulation of El Tor strains in the laboratory. In contrast, the prototypical classical strain O395 lacks this ability, which was suspected to be due to a mutation in the regulatory gene hapR HapR and the regulator TfoX control expression of a third competence regulator, QstR. We found that artificial induction of both TfoX and QstR in the presence of HapR in O395 was required for efficient DNA uptake. However, natural transformation in the classical strain is still orders of magnitude below that of an El Tor strain. O395 expressing HapR could also undergo natural transformation after growth on chitin, which could be increased by artificial induction of TfoX and/or QstR. A plasmid that expresses both TfoX and QstR was created that allowed for consistent DNA uptake in O395 carrying a hapR plasmid. This technique was also used to facilitate cotransformation into O395 of unmarked DNA (ΔlacZ, ΔflaA, ΔflgG) for multiplex genome editing by natural transformation (MuGENT). These results demonstrate that the classical biotype O395 strain is functionally capable of DNA uptake, which allows for the rapid genetic manipulation of its genome.IMPORTANCE Natural transformation (uptake of exogenous DNA) in Vibrio cholerae has contributed to the evolution of these human pathogens. Classical biotype V. cholerae strains were responsible for the first six cholera pandemics but were replaced by El Tor biotype V. cholerae in the current pandemic. This study demonstrates that classical V. cholerae is functionally capable of natural transformation, but inactivation of the transformation regulator HapR and inherent levels of transformation that are lower than those of El Tor V. cholerae suggest that the classical biotype may be less able to utilize natural transformation for horizontal gene transfer.
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Chen S, Sun S, Korfanty GA, Liu J, Xiang H. A Halocin Promotes DNA Uptake in Haloferax mediterranei. Front Microbiol 2019; 10:1960. [PMID: 31620096 PMCID: PMC6759562 DOI: 10.3389/fmicb.2019.01960] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 08/09/2019] [Indexed: 11/13/2022] Open
Abstract
Halocins are antimicrobial peptides or proteins that are produced by halophilic archaea. Although their function in inhibiting the growth of closely related haloarchaeal strains is well known, other physiological functions of halocins have also been proposed in recent years. To unveil the possible function and mechanism of halocins in DNA uptake, the halocin H4 producing strain Haloferax mediterranei DF50-ΔEPS (incapable of EPS production) was used in this study. We found that deletion of the halH4 resulted in the strain DF50-ΔEPSΔhalH4 which exhibited loss of natural DNA uptake ability. Moreover, supernatants of the halocin producing strain were capable of inducing the ability to uptake DNA. Obviously, halocin is likely responsible for inducing DNA uptake. Cell surface ultrastructures of these strains are varied from strains DF50-ΔEPS to DF50-ΔEPSΔhalH4. The cell surface of strain DF50-ΔEPS is rough due to numerous pinholes, while that of the strain DF50-ΔEPSΔhalH4 is smooth without visible pinholes. The morphology of the halH4 complemented strain, DF50-ΔEPSΔhalH4::H4, shows an intermediate phenotype between strains DF50-ΔEPS and DF50-ΔEPSΔhalH4. We speculate that halocin H4 may accelerate DNA uptake by perforating the cell surface ultrastructure. The halocin H4 may represent a novel inducer or activator of DNA uptake in Hfx. mediterranei.
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Affiliation(s)
- Shaoxing Chen
- Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, College of Life Sciences, Anhui Normal University, Wuhu, China
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Siqi Sun
- Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, College of Life Sciences, Anhui Normal University, Wuhu, China
| | | | - Jingwen Liu
- Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, College of Life Sciences, Anhui Normal University, Wuhu, China
| | - Hua Xiang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
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Incompatibility of Vibrio fischeri Strains during Symbiosis Establishment Depends on Two Functionally Redundant hcp Genes. J Bacteriol 2019; 201:JB.00221-19. [PMID: 31331977 DOI: 10.1128/jb.00221-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 06/30/2019] [Indexed: 01/23/2023] Open
Abstract
Bacteria that have the capacity to fill the same niche will compete with one another for the space and resources available within an ecosystem. Such competition is heightened among different strains of the same bacterial species. Nevertheless, different strains often inhabit the same host. The molecular mechanisms that impact competition between different strains within the same host are poorly understood. To address this knowledge gap, the type VI secretion system (T6SS), which is a mechanism for bacteria to kill neighboring cells, was examined in the marine bacterium Vibrio fischeri Different strains of V. fischeri naturally colonize the light organ of the bobtail squid Euprymna scolopes The genome of FQ-A001, a T6SS-positive strain, features two hcp genes that are predicted to encode identical subunits of the T6SS. Coincubation assays showed that either hcp gene is sufficient for FQ-A001 to kill another strain via the T6SS in vitro Additionally, induction of hcp expression is sufficient to induce killing activity in an FQ-A001 mutant lacking both hcp genes. Squid colonization assays involving inocula of FQ-A001-derived strains mixed with ES114 revealed that both hcp genes must be deleted for FQ-A001 and ES114 to occupy the same space within the light organ. These experimental results provide insight into the genetic factors necessary for the T6SS of V. fischeri to function in vivo, thereby increasing understanding of the molecular mechanisms that impact strain diversity within a host.IMPORTANCE Different bacterial strains compete to occupy the same niche. The outcome of such competition can be affected by the type VI secretion system (T6SS), an intercellular killing mechanism of bacteria. Here an animal-bacterial symbiosis is used as a platform for study of the genetic factors that promote the T6SS-mediated killing of one strain by another. Identification of the molecular determinants of T6SS function in vivo contributes to the understanding of how different strains interact within a host.
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Jaskólska M, Stutzmann S, Stoudmann C, Blokesch M. QstR-dependent regulation of natural competence and type VI secretion in Vibrio cholerae. Nucleic Acids Res 2019; 46:10619-10634. [PMID: 30102403 PMCID: PMC6237807 DOI: 10.1093/nar/gky717] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2018] [Accepted: 07/31/2018] [Indexed: 11/17/2022] Open
Abstract
During growth on chitinous surfaces in its natural aquatic environment Vibrio cholerae develops natural competence for transformation and kills neighboring non-immune bacteria using a type VI secretion system (T6SS). Activation of these two phenotypes requires the chitin-induced regulator TfoX, but also integrates signals from quorum sensing via the intermediate regulator QstR, which belongs to the LuxR-type family of regulators. Here, we define the QstR regulon using RNA sequencing. Moreover, by mapping QstR binding sites using chromatin immunoprecipitation coupled with deep sequencing we demonstrate that QstR is a transcription factor that binds upstream of the up- and down-regulated genes. Like other LuxR-type family transcriptional regulators we show that QstR function is dependent on dimerization. However, in contrast to the well-studied LuxR-type biofilm regulator VpsT of V. cholerae, which requires the second messenger c-di-GMP, we show that QstR dimerization and function is c-di-GMP independent. Surprisingly, although ComEA, which is a periplasmic DNA-binding protein essential for transformation, is produced in a QstR-dependent manner, QstR-binding was not detected upstream of comEA suggesting the existence of a further regulatory pathway. Overall, these results provide detailed insights into the function of a key regulator of natural competence and type VI secretion in V. cholerae.
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Affiliation(s)
- Milena Jaskólska
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Sandrine Stutzmann
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Candice Stoudmann
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Melanie Blokesch
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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Glucose-Specific Enzyme IIA of the Phosphoenolpyruvate:Carbohydrate Phosphotransferase System Modulates Chitin Signaling Pathways in Vibrio cholerae. J Bacteriol 2017; 199:JB.00127-17. [PMID: 28461445 DOI: 10.1128/jb.00127-17] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 04/21/2017] [Indexed: 12/13/2022] Open
Abstract
In Vibrio cholerae, the genes required for chitin utilization and natural competence are governed by the chitin-responsive two-component system (TCS) sensor kinase ChiS. In the classical TCS paradigm, a sensor kinase specifically phosphorylates a cognate response regulator to activate gene expression. However, our previous genetic study suggested that ChiS stimulates the non-TCS transcriptional regulator TfoS by using mechanisms distinct from classical phosphorylation reactions (S. Yamamoto, J. Mitobe, T. Ishikawa, S. N. Wai, M. Ohnishi, H. Watanabe, and H. Izumiya, Mol Microbiol 91:326-347, 2014, https://doi.org/10.1111/mmi.12462). TfoS specifically activates the transcription of tfoR, encoding a small regulatory RNA essential for competence gene expression. Whether ChiS and TfoS interact directly remains unknown. To determine if other factors mediate the communication between ChiS and TfoS, we isolated transposon mutants that turned off tfoR::lacZ expression but possessed intact chiS and tfoS genes. We demonstrated an unexpected association of chitin-induced signaling pathways with the glucose-specific enzyme IIA (EIIAglc) of the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) for carbohydrate uptake and catabolite control of gene expression. Genetic and physiological analyses revealed that dephosphorylated EIIAglc inactivated natural competence and tfoR transcription. Chitin-induced expression of the chb operon, which is required for chitin transport and catabolism, was also repressed by dephosphorylated EIIAglc Furthermore, the regulation of tfoR and chb expression by EIIAglc was dependent on ChiS and intracellular levels of ChiS were not affected by disruption of the gene encoding EIIAglc These results define a previously unknown connection between the PTS and chitin signaling pathways in V. cholerae and suggest a strategy whereby this bacterium can physiologically adapt to the existing nutrient status.IMPORTANCE The EIIAglc protein of the PTS coordinates a wide variety of physiological functions with carbon availability. In this report, we describe an unexpected association of chitin-activated signaling pathways in V. cholerae with EIIAglc The signaling pathways are governed by the chitin-responsive TCS sensor kinase ChiS and lead to the induction of chitin utilization and natural competence. We show that dephosphorylated EIIAglc inhibits both signaling pathways in a ChiS-dependent manner. This inhibition is different from classical catabolite repression that is caused by lowered levels of cyclic AMP. This work represents a newly identified connection between the PTS and chitin signaling pathways in V. cholerae and suggests a strategy whereby this bacterium can physiologically adapt to the existing nutrient status.
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Joshi A, Kostiuk B, Rogers A, Teschler J, Pukatzki S, Yildiz FH. Rules of Engagement: The Type VI Secretion System in Vibrio cholerae. Trends Microbiol 2017; 25:267-279. [PMID: 28027803 PMCID: PMC5365375 DOI: 10.1016/j.tim.2016.12.003] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 12/04/2016] [Accepted: 12/07/2016] [Indexed: 11/16/2022]
Abstract
Microbial species often exist in complex communities where they must avoid predation and compete for favorable niches. The type VI secretion system (T6SS) is a contact-dependent bacterial weapon that allows for direct killing of competitors through the translocation of proteinaceous toxins. Vibrio cholerae is a Gram-negative pathogen that can use its T6SS during antagonistic interactions with neighboring prokaryotic and eukaryotic competitors. The T6SS not only promotes V. cholerae's survival during its aquatic and host life cycles, but also influences its evolution by facilitating horizontal gene transfer. This review details the recent insights regarding the structure and function of the T6SS as well as the diverse signals and regulatory pathways that control its activation in V. cholerae.
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Affiliation(s)
- Avatar Joshi
- Department of Microbiology and Environmental Toxicology, University of Santa Cruz, Santa Cruz, California, USA
| | - Benjamin Kostiuk
- Department of Medical Microbiology and Immunology, University of Alberta, Alberta, Canada
| | - Andrew Rogers
- Department of Microbiology and Environmental Toxicology, University of Santa Cruz, Santa Cruz, California, USA
| | - Jennifer Teschler
- Department of Microbiology and Environmental Toxicology, University of Santa Cruz, Santa Cruz, California, USA
| | - Stefan Pukatzki
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Fitnat H Yildiz
- Department of Microbiology and Environmental Toxicology, University of Santa Cruz, Santa Cruz, California, USA.
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11
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Effects of Carbohydrate Source on Genetic Competence in Streptococcus mutans. Appl Environ Microbiol 2016; 82:4821-4834. [PMID: 27260355 DOI: 10.1128/aem.01205-16] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 05/25/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The capacity to internalize and catabolize carbohydrates is essential for dental caries pathogens to persist and cause disease. The expression of many virulence-related attributes by Streptococcus mutans, an organism strongly associated with human dental caries, is influenced by the peptide signaling pathways that control genetic competence. Here, we demonstrate a relationship between the efficiency of competence signaling and carbohydrate source. A significant increase in the activity of the promoters for comX, comS, and comYA after exposure to competence-stimulating peptide (CSP) was observed in cells growing on fructose, maltose, sucrose, or trehalose as the primary carbohydrate source, compared to cells growing on glucose. However, only cells grown in the presence of trehalose or sucrose displayed a significant increase in transformation frequency. Notably, even low concentrations of these carbohydrates in the presence of excess glucose could enhance the expression of comX, encoding a sigma factor needed for competence, and the effects on competence were dependent on the cognate sugar:phosphotransferase permease for each carbohydrate. Using green fluorescent protein (GFP) reporter fusions, we observed that growth in fructose or trehalose resulted in a greater proportion of the population activating expression of comX and comS, encoding the precursor of comX-inducing peptide (XIP), after addition of CSP, than growth in glucose. Thus, the source of carbohydrate significantly impacts the stochastic behaviors that regulate subpopulation responses to CSP, which can induce competence in S. mutans IMPORTANCE The signaling pathways that regulate development of genetic competence in Streptococcus mutans are intimately intertwined with the pathogenic potential of the organism, impacting biofilm formation, stress tolerance, and expression of known virulence determinants. Induction of the gene for the master regulator of competence, ComX, by competence-stimulating peptide (CSP) occurs in a subpopulation of cells. Here, we show that certain carbohydrates that are common in the human diet enhance the ability of CSP to activate transcription of comX and that a subset of these carbohydrates stimulates progression to the competent state. The cognate sugar:phosphotransferase permeases for each sugar are needed for these effects. Interestingly, single-cell analysis shows that the carbohydrates that increase com gene expression do so by enhancing the proportion of cells that respond to CSP. A mathematical model is developed to explain how carbohydrates modulate bistable behavior in the system via the ComRS pathway and ComX stability.
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12
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Metzger LC, Blokesch M. Regulation of competence-mediated horizontal gene transfer in the natural habitat of Vibrio cholerae. Curr Opin Microbiol 2015; 30:1-7. [PMID: 26615332 DOI: 10.1016/j.mib.2015.10.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 10/28/2015] [Accepted: 10/30/2015] [Indexed: 10/22/2022]
Abstract
The human pathogen Vibrio cholerae is an autochthonous inhabitant of aquatic environments where it often interacts with zooplankton and their chitinous molts. Chitin induces natural competence for transformation in V. cholerae, a key mode of horizontal gene transfer (HGT). Recent comparative genomic analyses were indicative of extensive HGT in this species. However, we can still expand our understanding of the complex regulatory network that drives competence in V. cholerae. Here, we present recent advances, including the elucidation of bipartite competence regulation mediated by QstR, the inclusion of the type VI secretion system in the competence regulon of pandemic O1 El Tor strains, and the identification of TfoS as a transcriptional regulator that links chitin to competence induction in V. cholerae.
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Affiliation(s)
- Lisa C Metzger
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Station 19, EPFL-SV-UPBLO, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Melanie Blokesch
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Station 19, EPFL-SV-UPBLO, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
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Matthey N, Blokesch M. The DNA-Uptake Process of Naturally Competent Vibrio cholerae. Trends Microbiol 2015; 24:98-110. [PMID: 26614677 DOI: 10.1016/j.tim.2015.10.008] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 10/05/2015] [Accepted: 10/22/2015] [Indexed: 10/22/2022]
Abstract
The sophisticated DNA-uptake machinery used during natural transformation is still poorly characterized, especially in Gram-negative bacteria where the transforming DNA has to cross two membranes as well as the peptidoglycan layer before entering the cytoplasm. The DNA-uptake machinery was hypothesized to take the form of a pseudopilus, which, upon repeated cycles of extension and retraction, would pull external DNA towards the cell surface or into the periplasmic space, followed by translocation across the cytoplasmic membrane. In this review, we summarize recent advances on the DNA-uptake machinery of V. cholerae, highlighting the presence of an extended competence-induced pilus and the contribution of a conserved DNA-binding protein that acts as a ratchet and reels DNA into the periplasm.
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Affiliation(s)
- Noémie Matthey
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Station 19, EPFL-SV-UPBLO, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Melanie Blokesch
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Station 19, EPFL-SV-UPBLO, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
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Watve SS, Thomas J, Hammer BK. CytR Is a Global Positive Regulator of Competence, Type VI Secretion, and Chitinases in Vibrio cholerae. PLoS One 2015; 10:e0138834. [PMID: 26401962 PMCID: PMC4581735 DOI: 10.1371/journal.pone.0138834] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 09/03/2015] [Indexed: 11/18/2022] Open
Abstract
The facultative pathogen Vibrio cholerae transitions between its human host and aquatic reservoirs where it colonizes chitinous surfaces. Growth on chitin induces expression of chitin utilization genes, genes involved in DNA uptake by natural transformation, and a type VI secretion system that allows contact-dependent killing of neighboring bacteria. We have previously shown that the transcription factor CytR, thought to primarily regulate the pyrimidine nucleoside scavenging response, is required for natural competence in V. cholerae. Through high-throughput RNA sequencing (RNA-seq), we show that CytR positively regulates the majority of competence genes, the three type VI secretion operons, and the four known or predicted chitinases. We used transcriptional reporters and phenotypic analysis to determine the individual contributions of quorum sensing, which is controlled by the transcription factors HapR and QstR; chitin utilization that is mediated by TfoX; and pyrimidine starvation that is orchestrated by CytR, toward each of these processes. We find that in V. cholerae, CytR is a global regulator of multiple behaviors affecting fitness and adaptability in the environment.
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Affiliation(s)
- Samit S. Watve
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America
| | - Jacob Thomas
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America
| | - Brian K. Hammer
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America
- * E-mail:
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