scholarly journals Abiotic factors modulate interspecies competition mediated by the type VI secretion system effectors in Vibrio cholerae

2021 ◽  
Author(s):  
Ming-Xuan Tang ◽  
Tao Dong ◽  
Tong-tong Pei ◽  
Zeng-Hang Wang ◽  
Han Luo ◽  
...  
Keyword(s):  
Stress Response ◽  
Vibrio Cholerae ◽  
Divalent Cations ◽  
Abiotic Factors ◽  
Secretion System ◽  
Type Vi Secretion System ◽  
Natural Habitats ◽  
Interspecies Competition ◽  
E Coli ◽  
Type Vi Secretion

Vibrio cholerae, the etiological pathogen of cholera, relies on its type VI secretion system (T6SS) as an effective weapon to survive in highly competitive communities. The anti-bacterial and anti-eukaryotic functions of T6SS depend on its secreted effectors that target multiple essential cellular processes. However, the mechanisms that account for effector diversity and different effectiveness during interspecies competition remain elusive. Here, we report that environmental cations and temperature play a key role in dictating effector-mediated competition of Vibrio cholerae. We found that V. cholerae could employ its cell-wall-targeting effector TseH to outcompete the otherwise resistant Escherichia coli and the V. cholerae immunity deletion mutant ∆tsiH when Ca2+ and Mg2+ were supplemented. The E. coli ∆phoQ mutant was more sensitive to TseH-mediated killing during competition, suggesting the metal-sensing PhoPQ two-component system is protective to E. coli from TseH activity. Using transcriptome analysis, we found multiple stress response systems, including acid stress response, oxidative stress response, and osmotic stress response, were activated in E. coli expressing TseH in comparison with E. coli expressing the inactive mutant TseHH64A. The membrane-targeting lipase effector TseL also exhibited reduced killing against E. coli when divalent cations were removed. In addition, competition analysis of E. coli with V. cholerae single-effector active strains reveals a temperature-dependent susceptibility of E. coli to effectors, VasX, VgrG3, and TseL. These findings suggest that abiotic factors, that V. cholerae frequently encounters in natural habitats, play a crucial role in dictating the competitive fitness conferred by the type VI secretion system in complex multispecies communities.

scholarly journals Vibrio cholerae Type VI Secretion System Auxiliary Cluster 3 is a Pandemic-associated Mobile Genetic Element

2019 ◽  
Author(s):  
Francis J. Santoriello ◽  
Lina Michel ◽  
Daniel Unterweger ◽  
Stefan Pukatzki
Keyword(s):  
Vibrio Cholerae ◽  
Horizontal Transfer ◽  
Mobile Genetic Element ◽  
Genomic Analysis ◽  
Secretion System ◽  
Specific Factor ◽  
Genetic Element ◽  
Type Vi Secretion System ◽  
Site Specific ◽  
Type Vi Secretion

AbstractAll sequenced Vibrio cholerae isolates encode a contact-dependent type VI secretion system (T6SS) in three loci that terminate in a toxic effector and cognate immunity protein (E/I) pair, allowing for competitor killing and clonal expansion in aquatic environments and the host gut. Recent studies have demonstrated variability in the toxic effectors produced by different V. cholerae strains and the propensity for effector genes to undergo horizontal gene transfer. Here we demonstrate that a fourth cluster, auxiliary cluster 3 (Aux3), encoding the E/I pair tseH/tsiH, is located directly downstream from two putative recombinases and is flanked by repeat elements resembling att sites. Genomic analysis of 749 V. cholerae isolates, including both pandemic and environmental strains, revealed that Aux3 exists in two states: a ∼40 kb prophage-like element in nine environmental isolates and a ∼6 kb element in pandemic isolates. These findings indicate that Aux3 in pandemic V. cholerae is evolutionarily related to an environmental prophage-like element. In both states, Aux3 excises from the chromosome via site-specific recombination to form a circular product, likely priming the module for horizontal transfer. Finally, we show that Aux3 can integrate into the Aux3-naïve chromosome in an integrase-dependent, site-specific manner. This highlights the potential of Aux3 to undergo horizontal transfer by a phage-like mechanism, which based on pandemic coincidence may confer currently unknown fitness advantages to the recipient V. cholerae cell.Significance StatementV. cholerae is a human pathogen that causes pandemics affecting 2.8 million people annually (1). The O1 El Tor lineage is responsible for the current pandemic. A subset of non-O1 strains cause cholera-like disease by producing the major virulence factors cholera toxin and toxin co-regulated pilus but fail to cause pandemics. The full set of V. cholerae pandemic factors is unknown. Here we describe the type VI secretion system (T6SS) Aux3 element as a largely pandemic-specific factor that is evolutionarily related to an environmental prophage-like element circulating in non-pathogenic strains. These findings shed light on V. cholerae T6SS evolution and indicate the Aux3 element as a pandemic-enriched mobile genetic element.

scholarly journals Fur-Dam Regulatory Interplay at an Internal Promoter of the Enteroaggregative Escherichia coli Type VI Secretion sci1 Gene Cluster

2020 ◽  
Vol 202 (10) ◽  
Author(s):  
Yannick R. Brunet ◽  
Christophe S. Bernard ◽  
Eric Cascales
Keyword(s):  
Escherichia Coli ◽  
Gene Cluster ◽  
Gene Clusters ◽  
Secretion System ◽  
Target Cells ◽  
Type Vi Secretion System ◽  
Content Type ◽  
Internal Promoter ◽  
E Coli ◽  
Type Vi Secretion

ABSTRACT The type VI secretion system (T6SS) is a weapon for delivering effectors into target cells that is widespread in Gram-negative bacteria. The T6SS is a highly versatile machine, as it can target both eukaryotic and prokaryotic cells, and it has been proposed that T6SSs are adapted to the specific needs of each bacterium. The expression of T6SS gene clusters and the activation of the secretion apparatus are therefore tightly controlled. In enteroaggregative Escherichia coli (EAEC), the sci1 T6SS gene cluster is subject to a complex regulation involving both the ferric uptake regulator (Fur) and DNA adenine methylase (Dam)-dependent DNA methylation. In this study, an additional, internal, promoter was identified within the sci1 gene cluster using +1 transcriptional mapping. Further analyses demonstrated that this internal promoter is controlled by a mechanism strictly identical to that of the main promoter. The Fur binding box overlaps the −10 transcriptional element and a Dam methylation site, GATC-32. Hence, the expression of the distal sci1 genes is repressed and the GATC-32 site is protected from methylation in iron-rich conditions. The Fur-dependent protection of GATC-32 was confirmed by an in vitro methylation assay. In addition, the methylation of GATC-32 negatively impacted Fur binding. The expression of the sci1 internal promoter is therefore controlled by iron availability through Fur regulation, whereas Dam-dependent methylation maintains a stable ON expression in iron-limited conditions. IMPORTANCE Bacteria use weapons to deliver effectors into target cells. One of these weapons, the type VI secretion system (T6SS), assembles a contractile tail acting as a spring to propel a toxin-loaded needle. Its expression and activation therefore need to be tightly regulated. Here, we identified an internal promoter within the sci1 T6SS gene cluster in enteroaggregative E. coli. We show that this internal promoter is controlled by Fur and Dam-dependent methylation. We further demonstrate that Fur and Dam compete at the −10 transcriptional element to finely tune the expression of T6SS genes. We propose that this elegant regulatory mechanism allows the optimum production of the T6SS in conditions where enteroaggregative E. coli encounters competing species.

scholarly journals Type VI Secretion System Dynamics Reveals a Novel Secretion Mechanism in Pseudomonas aeruginosa

2018 ◽  
Vol 200 (11) ◽  
Author(s):  
Jacqueline Corbitt ◽  
Jun Seok Yeo ◽  
C. Ian Davis ◽  
Michele LeRoux ◽  
Paul A. Wiggins
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Vibrio Cholerae ◽  
Conformational Change ◽  
Secretion System ◽  
Force Generation ◽  
Type Vi Secretion System ◽  
Content Type ◽  
Evolutionary Diversification ◽  
Type Vi Secretion ◽  
Generation Mechanisms

ABSTRACT The type VI secretion system (T6SS) inhibits the growth of neighboring bacterial cells through a contact-mediated mechanism. Here, we describe a detailed characterization of the protein localization dynamics in the Pseudomonas aeruginosa T6SS. It has been proposed that the type VI secretion process is driven by a conformational-change-induced contraction of the T6SS sheath. However, although the contraction of an optically resolvable TssBC sheath and the subsequent localization of ClpV are observed in Vibrio cholerae , coordinated assembly and disassembly of TssB and ClpV are observed without TssB contraction in P. aeruginosa . These dynamics are inconsistent with the proposed contraction sheath model. Motivated by the phenomenon of dynamic instability, we propose a new model in which ATP hydrolysis, rather than conformational change, generates the force for secretion. IMPORTANCE The type VI secretion system (T6SS) is widely conserved among Gram-negative bacteria and is a central determinant of bacterial fitness in polymicrobial communities. The secretion system targets bacteria and secretes effectors that inhibit the growth of neighboring cells, using a contact-mediated-delivery system. Despite significant homology to the previously characterized Vibrio cholerae T6SS, our analysis reveals that effector secretion is driven by a distinct force generation mechanism in Pseudomonas aeruginosa . The presence of two distinct force generation mechanisms in T6SS represents an example of the evolutionary diversification of force generation mechanisms.

scholarly journals Horizontal Gene Transfer of Functional Type VI Killing Genes by Natural Transformation

mBio ◽  
2017 ◽  
Vol 8 (4) ◽  
Author(s):  
Jacob Thomas ◽  
Samit S. Watve ◽  
William C. Ratcliff ◽  
Brian K. Hammer
Keyword(s):  
Community Structure ◽  
Microbial Community ◽  
Vibrio Cholerae ◽  
Empirical Support ◽  
Secretion System ◽  
Type Vi Secretion System ◽  
Computational Simulations ◽  
Profound Impact ◽  
Type Vi Secretion ◽  
Dependent Type

ABSTRACT Horizontal gene transfer (HGT) can have profound effects on bacterial evolution by allowing individuals to rapidly acquire adaptive traits that shape their strategies for competition. One strategy for intermicrobial antagonism often used by Proteobacteria is the genetically encoded contact-dependent type VI secretion system (T6SS), a weapon used to kill heteroclonal neighbors by direct injection of toxic effectors. Here, we experimentally demonstrate that Vibrio cholerae can acquire new T6SS effector genes via horizontal transfer and utilize them to kill neighboring cells. Replacement of one or more parental alleles with novel effectors allows the recombinant strain to dramatically outcompete its parent. Using spatially explicit modeling, we examine how this process could affect the ecology and evolution of surface-attached microbial populations. HGT of T6SS effector-immunity pairs is risky: transformation brings a cell into conflict with its former clone mates but can be adaptive when superior T6SS alleles are acquired. More generally, we find that these costs and benefits are not symmetric and that high rates of HGT can act as a hedge against competitors with unpredictable T6SS efficacy. We conclude that antagonism and horizontal transfer drive successive rounds of weapon optimization and selective sweeps, dynamically shaping the composition of microbial communities. IMPORTANCE The contact-dependent type VI secretion system (T6SS) is frequently used by Proteobacteria to kill adjacent competitors. While DNA released by T6 killing can be horizontally acquired, it remains untested whether T6 genes themselves can be horizontally acquired and then utilized to compete with neighboring cells. Using naturally transformable Vibrio cholerae, we provide the first direct empirical support for the hypothesis that T6 genes are exchanged horizontally (e.g., from dead competitors) and functionally deployed to compete with neighboring cells. Using computational simulations, we also demonstrate that high rates of HGT can be adaptive, allowing V. cholerae to improve upon existing T6 weaponry and survive direct encounters with otherwise superior competitors. We anticipate that our evolutionary results are of broad microbiological relevance, applying to many bacteria capable of HGT that utilize the T6SS or similar antagonistic systems, and highlight the profound impact of HGT in shaping microbial community structure. IMPORTANCE The contact-dependent type VI secretion system (T6SS) is frequently used by Proteobacteria to kill adjacent competitors. While DNA released by T6 killing can be horizontally acquired, it remains untested whether T6 genes themselves can be horizontally acquired and then utilized to compete with neighboring cells. Using naturally transformable Vibrio cholerae, we provide the first direct empirical support for the hypothesis that T6 genes are exchanged horizontally (e.g., from dead competitors) and functionally deployed to compete with neighboring cells. Using computational simulations, we also demonstrate that high rates of HGT can be adaptive, allowing V. cholerae to improve upon existing T6 weaponry and survive direct encounters with otherwise superior competitors. We anticipate that our evolutionary results are of broad microbiological relevance, applying to many bacteria capable of HGT that utilize the T6SS or similar antagonistic systems, and highlight the profound impact of HGT in shaping microbial community structure.

scholarly journals Vibrio cholerae Requires the Type VI Secretion System Virulence Factor VasX To Kill Dictyostelium discoideum

2011 ◽  
Vol 79 (7) ◽  
pp. 2941-2949 ◽  
Author(s):  
Sarah T. Miyata ◽  
Maya Kitaoka ◽  
Teresa M. Brooks ◽  
Steven B. McAuley ◽  
Stefan Pukatzki
Keyword(s):  
Vibrio Cholerae ◽  
Dictyostelium Discoideum ◽  
Virulence Factor ◽  
Membrane Lipids ◽  
Gene Clusters ◽  
Secretion System ◽  
Type Vi Secretion System ◽  
Content Type ◽  
Enzymatic Function ◽  
Type Vi Secretion

ABSTRACTThe type VI secretion system (T6SS) is recognized as an important virulence mechanism in several Gram-negative pathogens. InVibrio cholerae, the causative agent of the diarrheal disease cholera, a minimum of three gene clusters—one main cluster and two auxiliary clusters—are required to form a functional T6SS apparatus capable of conferring virulence toward eukaryotic and prokaryotic hosts. Despite an increasing understanding of the components that make up the T6SS apparatus, little is known about the regulation of these genes and the gene products delivered by this nanomachine. VasH is an important regulator of theV. choleraeT6SS. Here, we present evidence that VasH regulates the production of a newly identified protein, VasX, which in turn requires a functional T6SS for secretion. Deletion ofvasXdoes not affect export or enzymatic function of the structural T6SS proteins Hcp and VgrG-1, suggesting that VasX is dispensable for the assembly of the physical translocon complex. VasX localizes to the bacterial membrane and interacts with membrane lipids. We present VasX as a novel virulence factor of the T6SS, as aV. choleraemutant lackingvasXexhibits a phenotype of attenuated virulence towardDictyostelium discoideum.

scholarly journals Screening for Inhibition of Vibrio cholerae VipA-VipB Interaction Identifies Small-Molecule Compounds Active against Type VI Secretion

2014 ◽  
Vol 58 (7) ◽  
pp. 4123-4130 ◽  
Author(s):  
Kun Sun ◽  
Jeanette Bröms ◽  
Moa Lavander ◽  
Bharat Kumar Gurram ◽  
Per-Anders Enquist ◽  
...  
Keyword(s):  
Vibrio Cholerae ◽  
Small Molecule ◽  
Secretion System ◽  
Eukaryotic Cells ◽  
Minimal Risk ◽  
Type Vi Secretion System ◽  
Content Type ◽  
Development Of Resistance ◽  
Type Vi Secretion ◽  
Bacterial Replication

ABSTRACTThe type VI secretion system (T6SS) is the most prevalent bacterial secretion system and an important virulence mechanism utilized by Gram-negative bacteria, either to target eukaryotic cells or to combat other microbes. The components show much variability, but some appear essential for the function, and two homologues, denoted VipA and VipB inVibrio cholerae, have been identified in all T6SSs described so far. Secretion is dependent on binding of an α-helical region of VipA to VipB, and in the absence of this binding, both components are degraded within minutes and secretion is ceased. The aim of the study was to investigate if this interaction could be blocked, and we hypothesized that such inhibition would lead to abrogation of T6S. A library of 9,600 small-molecule compounds was screened for their ability to block the binding of VipA-VipB in a bacterial two-hybrid system (B2H). After excluding compounds that showed cytotoxicity toward eukaryotic cells, that inhibited growth ofVibrio, or that inhibited an unrelated B2H interaction, 34 compounds were further investigated for effects on the T6SS-dependent secretion of hemolysin-coregulated protein (Hcp) or of phospholipase A1activity. Two compounds, KS100 and KS200, showed intermediate or strong effects in both assays. Analogues were obtained, and compounds with potent inhibitory effects in the assays and desirable physicochemical properties as predicted byin silicoanalysis were identified. Since the compounds specifically target a virulence mechanism without affecting bacterial replication, they have the potential to mitigate the virulence with minimal risk for development of resistance.

scholarly journals Constitutive Type VI Secretion System Expression Gives Vibrio cholerae Intra- and Interspecific Competitive Advantages

PLoS ONE ◽  
2012 ◽  
Vol 7 (10) ◽  
pp. e48320 ◽  
Author(s):  
Daniel Unterweger ◽  
Maya Kitaoka ◽  
Sarah T. Miyata ◽  
Verena Bachmann ◽  
Teresa M. Brooks ◽  
...  
Keyword(s):  
Vibrio Cholerae ◽  
Secretion System ◽  
Competitive Advantages ◽  
Type Vi Secretion System ◽  
Type Vi Secretion
Sign in / Sign up

Export Citation Format

Share Document