scholarly journals Conserved type VI secretion regulation in diverseVibriospecies by the regulatory proteins TfoX and TfoY

2018 ◽  
Author(s):  
Lisa C. Metzger ◽  
Noémie Matthey ◽  
Candice Stoudmann ◽  
Esther J. Collas ◽  
Melanie Blokesch
Keyword(s):  
Regulatory Proteins ◽  
Signalling Pathways ◽  
Type Vi Secretion System ◽  
Secretion Systems ◽  
Master Regulators ◽  
Type Vi Secretion ◽  
Regulatory Circuits ◽  
Surface Sensing ◽  
Macromolecular Protein ◽  
Insight Into

SummaryBacteria of the genusVibrioare common members of aquatic environments where they compete with other prokaryotes and defend themselves against grazing predators. A macromolecular protein complex called the type VI secretion system (T6SS) is used for both purposes. Previous research showed that the sole T6SS of the human pathogenV. choleraeis induced by extracellular (chitin) or intracellular (low c-di-GMP levels) cues and that these cues lead to distinctive signalling pathways for which the proteins TfoX and TfoY serve as master regulators. In this study, we tested whether the TfoX- and TfoY-mediated regulation of T6SS was conserved in non-cholera species, and if so, how these regulators affected the production of individual T6SSs in double-armed vibrios. We show that, alongside representative competence genes, TfoX regulates at least one T6SS in all testedVibriospecies. TfoY, on the other hand, fostered motility in all vibrios but had a more versatile T6SS response in that it did not foster T6SS-mediated killing inV. fischeriwhile it induced both systems inV. alginolyticus. Collectively, our data provide evidence that the TfoX- and TfoY-mediated signalling pathways are mostly conserved in diverseVibriospecies and important for signal-specific T6SS induction.Originality-Significance StatementThis work provides new insight into the regulatory circuits involved in type VI secretion in diverseVibriospecies. Specifically, it is the first study to compare the effects of the two regulatory proteins TfoX and TfoY on the primary or secondary type VI secretion systems of non-cholera vibrios. Importantly, this work also shows that decreased c-di-GMP levels inV. parahaemolyticuslead to TfoY production without changingtfoYtranscript levels, thereby indirectly linking TfoY production to surface sensing.

scholarly journals A family of T6SS antibacterial effectors related to L,D-transpeptidases targets the Peptidoglycan

2020 ◽  
Vol 2 (7A) ◽  
Author(s):  
Stephanie Sibinelli de Sousa ◽  
Julia Takuno Hespanhol ◽  
Bruno Matsuyama ◽  
Stephane Mesnage ◽  
Gianlucca Nicastro ◽  
...  
Keyword(s):  
Cell Envelope ◽  
Point Mutations ◽  
Time Lapse ◽  
Secretion Systems ◽  
Bacterial Antagonism ◽  
New Family ◽  
Type Vi Secretion ◽  
Altered Cell ◽  
Bacterial Effectors ◽  
Insight Into

Type VI secretion systems (T6SSs) are contractile nanomachines widely used by bacteria to intoxicate competitors. Salmonella Typhimurium encodes a T6SS within the Salmonella pathogenicity island 6 (SPI-6) that is used during competition against species of the gut microbiota. We characterized a new SPI-6 T6SS antibacterial effector named Tlde1 (type VI L,D-transpeptidase effector 1). Tlde1 is toxic in target-cell periplasm and its toxicity is neutralized by co-expression with immunity protein Tldi1 (type VI L,D-transpeptidase immunity 1). Time-lapse microscopy revealed that intoxicated cells display altered cell division and lose cell envelope integrity. Bioinformatics analysis showed that Tlde1 is evolutionarily related to L,D-transpeptidases. Point mutations on conserved histidine121 and cysteine131 residues eliminated toxicity. Co-incubation of purified recombinant Tlde1 and peptidoglycan tetrapeptides showed that Tlde1 displays both L,D-carboxypeptidase activity by cleaving GM-tetrapeptides between meso-diaminopimelic acid3 and D-alanine4, and L,D-transpeptidase exchange activity by replacing D-alanine4 for a non-canonical D-amino acid. Tlde1 constitutes a new family of T6SS effectors widespread in Proteobacteria. This work increases our knowledge about the bacterial effectors used in interbacterial competitions and provides molecular insight into a new mechanism of bacterial antagonism.

scholarly journals Baseplate assembly of phage Mu: Defining the conserved core components of contractile-tailed phages and related bacterial systems

2016 ◽  
Vol 113 (36) ◽  
pp. 10174-10179 ◽  
Author(s):  
Carina R. Büttner ◽  
Yingzhou Wu ◽  
Karen L. Maxwell ◽  
Alan R. Davidson
Keyword(s):  
Type Vi Secretion System ◽  
Secretion Systems ◽  
Phage Mu ◽  
Self Defense ◽  
Type Vi Secretion ◽  
Essential Components ◽  
Core Components ◽  
Contractile Tail ◽  
Equivalent Structure ◽  
Conserved Core

Contractile phage tails are powerful cell puncturing nanomachines that have been co-opted by bacteria for self-defense against both bacteria and eukaryotic cells. The tail of phage T4 has long served as the paradigm for understanding contractile tail-like systems despite its greater complexity compared with other contractile-tailed phages. Here, we present a detailed investigation of the assembly of a “simple” contractile-tailed phage baseplate, that of Escherichia coli phage Mu. By coexpressing various combinations of putative Mu baseplate proteins, we defined the required components of this baseplate and delineated its assembly pathway. We show that the Mu baseplate is constructed through the independent assembly of wedges that are organized around a central hub complex. The Mu wedges are comprised of only three protein subunits rather than the seven found in the equivalent structure in T4. Through extensive bioinformatic analyses, we found that homologs of the essential components of the Mu baseplate can be identified in the majority of contractile-tailed phages and prophages. No T4-like prophages were identified. The conserved simple baseplate components were also found in contractile tail-derived bacterial apparatuses, such as type VI secretion systems, Photorhabdus virulence cassettes, and R-type tailocins. Our work highlights the evolutionary connections and similarities in the biochemical behavior of phage Mu wedge components and the TssF and TssG proteins of the type VI secretion system. In addition, we demonstrate the importance of the Mu baseplate as a model system for understanding bacterial phage tail-derived systems.

scholarly journals A new family of Type VI secretion system-delivered effector proteins displays ion-selective pore-forming activity

2019 ◽  
Author(s):  
Giuseppina Mariano ◽  
Katharina Trunk ◽  
David J. Williams ◽  
Laura Monlezun ◽  
Henrik Strahl ◽  
...  
Keyword(s):  
Effector Proteins ◽  
Type Vi Secretion System ◽  
Secretion Systems ◽  
New Family ◽  
Type Vi Secretion ◽  
Outer Membrane Permeability ◽  
Polymicrobial Communities ◽  
Bacterial Effectors

AbstractType VI secretion systems (T6SSs) are nanomachines widely used by bacteria to compete with rivals. T6SSs deliver multiple toxic effector proteins directly into neighbouring cells and play key roles in shaping diverse polymicrobial communities. A number of families of T6SS-dependent anti-bacterial effectors have been characterised, however the mode of action of others remains unknown. Here we report that Ssp6, an anti-bacterial effector delivered by theSerratia marcescensT6SS, is an ion-selective pore-forming toxin.In vivo, Ssp6 inhibits growth by causing depolarisation of the inner membrane of intoxicated cells and also leads to increased outer membrane permeability, whilst reconstruction of Ssp6 activityin vitrodemonstrated that it forms cation-selective pores. A survey of bacterial genomes revealed that Ssp6-like effectors are widespread in Enterobacteriaceae and often linked with T6SS genes. We conclude that Ssp6 represents a new family of T6SS-delivered anti-bacterial effectors, further diversifying the portfolio of weapons available for deployment during inter-bacterial conflict.

scholarly journals VipA N-terminal linker and VipB-VipB interaction modulate the contraction of Type VI secretion system sheath

2017 ◽  
Author(s):  
Maximilian Brackmann ◽  
Jing Wang ◽  
Marek Basler
Keyword(s):  
Protein Translocation ◽  
Secretion System ◽  
Mass Spectrometry Analysis ◽  
Target Cells ◽  
Extended State ◽  
Type Vi Secretion System ◽  
Secretion Systems ◽  
Spectrometry Analysis ◽  
Type Vi Secretion ◽  
Bacterial Type

AbstractSecretion systems are essential for bacteria to survive and manipulate their environment. The bacterial Type VI Secretion System (T6SS) generates the force needed for protein translocation by the contraction of a long polymer called sheath, which is composed of interconnected VipA/VipB subunits forming a six-start helix. The mechanism of T6SS sheath contraction and the structure of its extended state are unknown. Here we show that elongating the N-terminal VipA linker or eliminating charge of a specific VipB residue abolished sheath contraction and delivery of effectors into target cells. The assembly of the non-contractile sheaths was dependent on the baseplate component TssE and mass-spectrometry analysis identified Hcp, VgrG and other components of the T6SS baseplate specifically associated with stable non-contractile sheaths. The ability to lock T6SS in the pre-firing state opens new possibilities for understanding its mode of action.

scholarly journals A family of Type VI secretion system effector proteins that form ion-selective pores

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Giuseppina Mariano ◽  
Katharina Trunk ◽  
David J. Williams ◽  
Laura Monlezun ◽  
Henrik Strahl ◽  
...  
Keyword(s):  
Opportunistic Pathogen ◽  
Effector Proteins ◽  
Type Vi Secretion System ◽  
Secretion Systems ◽  
New Family ◽  
Type Vi Secretion ◽  
Genes Encoding ◽  
Outer Membrane Permeability ◽  
Bacterial Effectors

AbstractType VI secretion systems (T6SSs) are nanomachines widely used by bacteria to deliver toxic effector proteins directly into neighbouring cells. However, the modes of action of many effectors remain unknown. Here we report that Ssp6, an anti-bacterial effector delivered by a T6SS of the opportunistic pathogen Serratia marcescens, is a toxin that forms ion-selective pores. Ssp6 inhibits bacterial growth by causing depolarisation of the inner membrane in intoxicated cells, together with increased outer membrane permeability. Reconstruction of Ssp6 activity in vitro demonstrates that it forms cation-selective pores. A survey of bacterial genomes reveals that genes encoding Ssp6-like effectors are widespread in Enterobacteriaceae and often linked with T6SS genes. We conclude that Ssp6 and similar proteins represent a new family of T6SS-delivered anti-bacterial effectors.

scholarly journals Crosstalk between the Type VI Secretion System and the Expression of Class IV Flagellar Genes in the Pseudomonas fluorescens MFE01 Strain

2020 ◽  
Vol 8 (5) ◽  
pp. 622 ◽  
Author(s):  
Mathilde Bouteiller ◽  
Mathias Gallique ◽  
Yvann Bourigault ◽  
Artemis Kosta ◽  
Julie Hardouin ◽  
...  
Keyword(s):  
Pseudomonas Fluorescens ◽  
Sigma Factor ◽  
Type Vi Secretion System ◽  
Secretion Systems ◽  
Gene Encoding ◽  
Prey Cell ◽  
Over Expression ◽  
Type Vi Secretion ◽  
Flagellar Genes ◽  
Class Iv

Type VI secretion systems (T6SSs) are contractile bacterial multiprotein nanomachines that enable the injection of toxic effectors into prey cells. The Pseudomonas fluorescens MFE01 strain has T6SS antibacterial activity and can immobilise competitive bacteria through the T6SS. Hcp1 (hemolysin co-regulated protein 1), a constituent of the T6SS inner tube, is involved in such prey cell inhibition of motility. Paradoxically, disruption of the hcp1 or T6SS contractile tail tssC genes results in the loss of the mucoid and motile phenotypes in MFE01. Here, we focused on the relationship between T6SS and flagella-associated motility. Electron microscopy revealed the absence of flagellar filaments for MFE01Δhcp1 and MFE01ΔtssC mutants. Transcriptomic analysis showed a reduction in the transcription of class IV flagellar genes in these T6SS mutants. However, transcription of fliA, the gene encoding the class IV flagellar sigma factor, was unaffected. Over-expression of fliA restored the motile and mucoid phenotypes in both MFE01Δhcp1+fliA, and MFE01ΔtssC+fliA and a fliA mutant displayed the same phenotypes as MFE01Δhcp1 and MFE01ΔtssC. Moreover, the FliA anti-sigma factor FlgM was not secreted in the T6SS mutants, and flgM over-expression reduced both motility and mucoidy. This study provides arguments to unravel the crosstalk between T6SS and motility.

scholarly journals H-NS regulates the Vibrio parahaemolyticus type VI secretion system 1

Microbiology ◽  
2014 ◽  
Vol 160 (9) ◽  
pp. 1867-1873 ◽  
Author(s):  
Dor Salomon ◽  
John A. Klimko ◽  
Kim Orth
Keyword(s):  
Gene Cluster ◽  
Vibrio Parahaemolyticus ◽  
Secretion System ◽  
Type Vi Secretion System ◽  
Environmental Signals ◽  
Type Vi Secretion ◽  
Food Borne ◽  
Surface Sensing ◽  
Transcription Regulators ◽  
System 1

The marine bacterium Vibrio parahaemolyticus, a major cause of food-borne gastroenteritis, employs a type VI secretion system 1 (T6SS1), a recently discovered protein secretion system, to combat competing bacteria. Environmental signals such as temperature, salinity, cell density and surface sensing, as well as the quorum-sensing master regulator OpaR, were previously reported to regulate T6SS1 activity and expression. In this work, we set out to identify additional transcription regulators that control the tightly regulated T6SS1 activity. To this end, we determined the effect of deletions in several known virulence regulators and in two regulators encoded within the T6SS1 gene cluster on expression and secretion of the core T6SS component Hcp1 and on T6SS1-mediated anti-bacterial activity. We report that VP1391 and VP1407, transcriptional regulators encoded within the T6SS1 gene cluster, are essential for T6SS1 activity. Moreover, we found that H-NS, a bacterial histone-like nucleoid structuring protein, which mediates transcription silencing of horizontally acquired genes, serves as a repressor of T6SS1. We also show that activation of surface sensing and high salt conditions alleviate the H-NS-mediated repression. Our results shed light on the complex network of environmental signals and transcription regulators that govern the tight regulation over T6SS1 activity.

scholarly journals The Francisella Pathogenicity Island Protein PdpD Is Required for Full Virulence and Associates with Homologues of the Type VI Secretion System

2008 ◽  
Vol 190 (13) ◽  
pp. 4584-4595 ◽  
Author(s):  
Jagjit S. Ludu ◽  
Olle M. de Bruin ◽  
Barry N. Duplantis ◽  
Crystal L. Schmerk ◽  
Alicia Y. Chou ◽  
...  
Keyword(s):  
North America ◽  
Outer Membrane ◽  
Bacterial Pathogen ◽  
Pathogenicity Island ◽  
Secretion System ◽  
Type Vi Secretion System ◽  
Secretion Systems ◽  
Intracellular Growth ◽  
Type Vi Secretion ◽  
Genes Encoding

ABSTRACT Francisella tularensis is a highly infectious, facultative intracellular bacterial pathogen that is the causative agent of tularemia. Nearly a century ago, researchers observed that tularemia was often fatal in North America but almost never fatal in Europe and Asia. The chromosomes of F. tularensis strains carry two identical copies of the Francisella pathogenicity island (FPI), and the FPIs of North America-specific biotypes contain two genes, anmK and pdpD, that are not found in biotypes that are distributed over the entire Northern Hemisphere. In this work, we studied the contribution of anmK and pdpD to virulence by using F. novicida, which is very closely related to F. tularensis but which carries only one copy of the FPI. We showed that anmK and pdpD are necessary for full virulence but not for intracellular growth. This is in sharp contrast to most other FPI genes that have been studied to date, which are required for intracellular growth. We also showed that PdpD is localized to the outer membrane. Further, overexpression of PdpD affects the cellular distribution of FPI-encoded proteins IglA, IglB, and IglC. Finally, deletions of FPI genes encoding proteins that are homologues of known components of type VI secretion systems abolished the altered distribution of IglC and the outer membrane localization of PdpD.

scholarly journals Type VI secretion system killing by commensal Neisseria is influenced by the spatial dynamics of bacteria

2020 ◽  
Author(s):  
Rafael Custodio ◽  
Rhian M. Ford ◽  
Cara J. Ellison ◽  
Guangyu Liu ◽  
Gerda Mickute ◽  
...  
Keyword(s):  
Spatial Dynamics ◽  
Secretion System ◽  
Type Vi Secretion System ◽  
Secretion Systems ◽  
Spatial Constraints ◽  
Human Respiratory Tract ◽  
Type Vi Secretion ◽  
Close Proximity ◽  
The Impact ◽  
Commensal Neisseria

ABSTRACTType VI Secretion Systems (T6SS) are widespread in bacteria and can dictate the development and organisation of polymicrobial ecosystems by mediating contact dependent killing. In Neisseria species, including Neisseria cinerea a commensal of the human respiratory tract, interbacterial contacts are mediated by Type four pili (Tfp) which promote formation of aggregates and govern the spatial dynamics of growing Neisseria microcolonies. Here we show that N. cinerea expresses a plasmid-encoded T6SS that is active and can limit growth of related pathogens. We explored the impact of Tfp expression on N. cinerea T6SS-dependent killing and show that expression of Tfp by prey strains enhances their susceptibility to T6SS, by keeping them in close proximity of T6SS-wielding attacker strains. Our findings have important implications for understanding how spatial constraints during contact-dependent antagonism can shape the evolution of microbial communities.

scholarly journals Host Adaptation Predisposes Pseudomonas aeruginosa to Type VI Secretion System-Mediated Predation by the Burkholderia cepacia Complex

2020 ◽  
Author(s):  
Andrew I Perault ◽  
Courtney E Chandler ◽  
David A Rasko ◽  
Robert K Ernst ◽  
Matthew C Wolfgang ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Burkholderia Cepacia ◽  
Secretion System ◽  
Burkholderia Cenocepacia ◽  
Burkholderia Cepacia Complex ◽  
Dependent Manner ◽  
Type Vi Secretion System ◽  
Secretion Systems ◽  
Type Vi Secretion

SUMMARYPseudomonas aeruginosa (Pa) and Burkholderia cepacia complex (Bcc) species are opportunistic lung pathogens of individuals with cystic fibrosis (CF). While Pa can initiate long-term infections in younger CF patients, Bcc infections only arise in teenagers and adults. Both Pa and Bcc use type VI secretion systems (T6SS) to mediate interbacterial competition. Here, we show that Pa isolates from teenage/adult CF patients, but not those from young CF patients, are outcompeted by the epidemic Bcc isolate Burkholderia cenocepacia strain AU1054 (BcAU1054) in a T6SS-dependent manner. The genomes of susceptible Pa isolates harbor T6SS-abrogating mutations, the repair of which, in some cases, rendered the isolates resistant. Moreover, seven of eight Bcc strains outcompeted Pa strains isolated from the same patients. Our findings suggest that certain mutations that arise as Pa adapts to the CF lung abrogate T6SS activity, making Pa and its human host susceptible to potentially fatal Bcc superinfection.

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