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 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 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 Mutations in Salmonella Pathogenicity Island 2 (SPI2) Genes Affecting Transcription of SPI1 Genes and Resistance to Antimicrobial Agents

1998 ◽  
Vol 180 (18) ◽  
pp. 4775-4780 ◽  
Author(s):  
Jörg Deiwick ◽  
Thomas Nikolaus ◽  
Jaqueline E. Shea ◽  
Colin Gleeson ◽  
David W. Holden ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Antimicrobial Agents ◽  
Type Iii Secretion System ◽  
Polymyxin B ◽  
Secretion System ◽  
Effector Proteins ◽  
Secretion Systems ◽  
Type Iii ◽  
Genes Encoding

ABSTRACT The Salmonella typhimurium genome contains two pathogenicity islands (SPI) with genes encoding type III secretion systems for virulence proteins. SPI1 is required for the penetration of the epithelial layer of the intestine. SPI2 is important for the subsequent proliferation of bacteria in the spleens of infected hosts. Although most mutations in SPI2 lead to a strong reduction of virulence, they have different effects in vitro, with some mutants having significantly increased sensitivity to gentamicin and the antibacterial peptide polymyxin B. Previously we showed that certain mutations in SPI2 affect the ability of S. typhimurium to secrete SPI1 effector proteins and to invade cultured eukaryotic cells. In this study, we show that these SPI2 mutations affect the expression of the SPI1 invasion genes. Analysis of reporter fusions to various SPI1 genes reveals highly reduced expression of sipC,prgK, and hilA, the transcriptional activator of SPI1 genes. These observations indicate that the expression of one type III secretion system can be influenced dramatically by mutations in genes encoding a second type III secretion system in the same cell.

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 TheVibrio choleraeType VI Secretion System Can Modulate Host Intestinal Mechanics to Displace Commensal Gut Bacteria

2017 ◽  
Author(s):  
Savannah L. Logan ◽  
Jacob Thomas ◽  
Jinyuan Yan ◽  
Ryan P. Baker ◽  
Drew S. Shields ◽  
...  
Keyword(s):  
Secretion System ◽  
Effector Proteins ◽  
Target Cells ◽  
Type Vi Secretion System ◽  
Zebrafish Model ◽  
Microbial Competition ◽  
Aeromonas Veronii ◽  
Type Vi Secretion ◽  
Commensal Strain

AbstractHost-associated microbiota help defend against bacterial pathogens; the mechanisms that pathogens possess to overcome this defense, however, remain largely unknown. We developed a zebrafish model and used live imaging to directly study how the human pathogenVibrio choleraeinvades the intestine. The gut microbiota of fish mono-colonized by commensal strainAeromonas veroniiwas displaced byV. choleraeexpressing its Type VI Secretion System (T6SS), a syringe-like apparatus that deploys effector proteins into target cells. Surprisingly, displacement was independent of T6SS-mediated killing ofAeromonas, driven instead by T6SS-induced enhancement of zebrafish intestinal movements that led to expulsion of the resident commensal by the host. Deleting an actin crosslinking domain from the T6SS apparatus returned intestinal motility to normal and thwarted expulsion, without weakeningV. cholerae′sability to killAeromonas in vitro. Our finding that bacteria can manipulate host physiology to influence inter-microbial competition has implications for both pathogenesis and microbiome engineering.

scholarly journals The Type VI Secretion System of Pseudomonas aeruginosa: a gun loaded with antimicrobial bullets

2020 ◽  
Vol 2 (7A) ◽  
Author(s):  
Sophie Howard ◽  
Chris Furniss ◽  
Dora Bonini ◽  
Himani Amin ◽  
Patricia Paracuellos-Torrecilla ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Respiratory Infections ◽  
Opportunistic Pathogen ◽  
Secretion System ◽  
Type Vi Secretion System ◽  
Type Vi Secretion ◽  
Interaction Partners ◽  
Bacterial Cytoplasm ◽  
Bacterial Effectors ◽  
Future Work

Pseudomonas aeruginosa is an opportunistic pathogen that can cause severe respiratory infections in people who are immunocompromised. P. aeruginosa possesses the Type VI Secretion System (T6SS), a bacterial weapon that injects effectors into neighbouring prokaryotes and eukaryotes. The T6SS is crucial for bacterial warfare, allowing P. aeruginosa to kill its competitors, which promotes its dominance in mixed microbial environments. P. aeruginosa has three T6SSs, H1/2/3-T6SS, these are structural homologs but deliver unique effectors. Effectors are delivered via the secreted component, a Hcp tube topped with a VgrG and PAAR spike. Only the first three identified effectors are delivered by Hcp1. Since then, there has been a bias in identification of VgrG or PAAR delivered effectors, mostly as these are encoded next to the spike proteins. Some P. aeruginosa effectors not only kill bacteria but have a dual role in pathogenesis. Our aim was to identify a comprehensive set of Hcp-delivered effectors for all three systems. Using Hcp1/2/3, systematic pull-down screens were performed to identify novel interaction partners. After confirming interaction, antibacterial toxicity was evaluated, identifying new Hcp delivered T6SS effectors for Hcp2 and Hcp3, which are toxic in the bacterial cytoplasm. These new anti-bacterial effectors may kill bacteria in novel ways, which could lead to novel antibiotics. Additionally, a toxin fusion proved too large for secretion and blocked the T6SS, revealing a Hcp-delivered effector size limit. Future work will focus on fully characterising these new toxins, as well as to look into the potential eukaryotic role of other interaction partners.

scholarly journals The Cluster 1 Type VI Secretion System Is a Major Virulence Determinant inBurkholderia pseudomallei

2011 ◽  
Vol 79 (4) ◽  
pp. 1512-1525 ◽  
Author(s):  
Mary N. Burtnick ◽  
Paul J. Brett ◽  
Sarah V. Harding ◽  
Sarah A. Ngugi ◽  
Wilson J. Ribot ◽  
...  
Keyword(s):  
Growth Defect ◽  
Raw 264.7 ◽  
Type Vi Secretion System ◽  
Secretion Systems ◽  
Lethal Challenge ◽  
Hamster Model ◽  
Raw 264.7 Macrophages ◽  
Link Type ◽  
Type Vi Secretion

ABSTRACTTheBurkholderia pseudomalleiK96243genome encodes six type VI secretion systems (T6SSs), but little is known about the role of these systems in the biology ofB. pseudomallei. In this study, we purified recombinant Hcp proteins from each T6SS and tested them as vaccine candidates in the BALB/c mouse model of melioidosis. Recombinant Hcp2 protected 80% of mice against a lethal challenge withK96243, while recombinant Hcp1, Hcp3, and Hcp6 protected 50% of mice against challenge. Hcp6 was the only Hcp constitutively produced byB. pseudomallei in vitro; however, it was not exported to the extracellular milieu. Hcp1, on the other hand, was produced and exportedin vitrowhen the VirAG two-component regulatory system was overexpressed intrans. We also constructed sixhcpdeletion mutants (Δhcp1throughΔhcp6) and tested them for virulence in the Syrian hamster model of infection. The 50% lethal doses (LD50s) for theΔhcp2throughΔhcp6mutants were indistinguishable fromK96243(<10 bacteria), but the LD50for theΔhcp1mutant was >103bacteria. Thehcp1deletion mutant also exhibited a growth defect in RAW 264.7 macrophages and was unable to form multinucleated giant cells in this cell line. UnlikeK96243, theΔhcp1mutant was only weakly cytotoxic to RAW 264.7 macrophages 18 h after infection. The results suggest that the cluster 1 T6SS is essential for virulence and plays an important role in the intracellular lifestyle ofB. pseudomallei.

scholarly journals The Ferric Uptake Regulator Represses Type VI Secretion System Function by Binding Directly to the clpV Promoter in Salmonella enterica Serovar Typhimurium

2019 ◽  
Vol 87 (10) ◽  
Author(s):  
Shaohui Wang ◽  
Denghui Yang ◽  
Xiaojun Wu ◽  
Zhengfei Yi ◽  
Yang Wang ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Transcriptional Start Site ◽  
Effector Proteins ◽  
Ferric Uptake Regulator ◽  
Type Vi Secretion System ◽  
Secretion Systems ◽  
Mobility Shift ◽  
Content Type ◽  
Type Vi Secretion ◽  
Serovar Typhimurium

ABSTRACT Type VI secretion systems (T6SSs) are highly conserved and complex protein secretion systems that deliver effector proteins into eukaryotic hosts or other bacteria. T6SSs are regulated precisely by a variety of regulatory systems, which enables bacteria to adapt to varied environments. A T6SS within Salmonella pathogenicity island 6 (SPI-6) is activated during infection, and it contributes to the pathogenesis, as well as interbacterial competition, of Salmonella enterica serovar Typhimurium (S. Typhimurium). However, the regulation of the SPI-6 T6SS in S. Typhimurium is not well understood. In this study, we found that the SPI-6 T6SS core gene clpV was significantly upregulated in response to the iron-depleted condition and during infection. The global ferric uptake regulator (Fur) was shown to repress the clpV expression in the iron-replete medium. Moreover, electrophoretic mobility shift and DNase I footprinting assays revealed that Fur binds directly to the clpV promoter region at multiple sites spanning the transcriptional start site. We also observed that the relieving of Fur-mediated repression on clpV contributed to the interbacterial competition activity and pathogenicity of S. Typhimurium. These findings provide insights into the direct regulation of Fur in the expression and functional activity of SPI-6 T6SS in S. Typhimurium and thus help to elucidate the mechanisms of bacterial adaptability and virulence.

scholarly journals Bacteroides fragilistype VI secretion systems use novel effector and immunity proteins to antagonize human gut Bacteroidales species

2016 ◽  
Vol 113 (13) ◽  
pp. 3627-3632 ◽  
Author(s):  
Maria Chatzidaki-Livanis ◽  
Naama Geva-Zatorsky ◽  
Laurie E. Comstock
Keyword(s):  
Secretion Systems ◽  
Human Gut ◽  
Variable Regions ◽  
Type Vi Secretion ◽  
Genes Encoding ◽  
T6ss Locus ◽  
Integrative Conjugative Elements ◽  
Mutation Analyses ◽  
Competition Assays

Type VI secretion systems (T6SSs) are multiprotein complexes best studied in Gram-negative pathogens where they have been shown to inhibit or kill prokaryotic or eukaryotic cells and are often important for virulence. We recently showed that T6SS loci are also widespread in symbiotic human gut bacteria of the order Bacteroidales, and that these T6SS loci segregate into three distinct genetic architectures (GA). GA1 and GA2 loci are present on conserved integrative conjugative elements (ICE) and are transferred and shared among diverse human gut Bacteroidales species. GA3 loci are not contained on conserved ICE and are confined toBacteroides fragilis. Unlike GA1 and GA2 T6SS loci, most GA3 loci do not encode identifiable effector and immunity proteins. Here, we studied GA3 T6SSs and show that they antagonize most human gut Bacteroidales strains analyzed, except forB. fragilisstrains with the same T6SS locus. A combination of mutation analyses,trans-protection analyses, and in vitro competition assays, allowed us to identify novel effector and immunity proteins of GA3 loci. These proteins are not orthologous to known proteins, do not contain identified motifs, and most have numerous predicted transmembrane domains. Because the genes encoding effector and immunity proteins are contained in two variable regions of GA3 loci, GA3 T6SSs of the speciesB. fragilisare likely the source of numerous novel effector and immunity proteins. Importantly, we show that the GA3 T6SS of strain 638R is functional in the mammalian gut and provides a competitive advantage to this organism.

scholarly journals Structural basis for effector transmembrane domain recognition by type VI secretion system chaperones

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Shehryar Ahmad ◽  
Kara K Tsang ◽  
Kartik Sachar ◽  
Dennis Quentin ◽  
Tahmid M Tashin ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Transmembrane Domain ◽  
Secretion System ◽  
Effector Proteins ◽  
Structural Basis ◽  
Type Vi Secretion System ◽  
Secretion Systems ◽  
Conserved Motif ◽  
Type Vi Secretion ◽  
Helical Packing

Type VI secretion systems (T6SSs) deliver antibacterial effector proteins between neighboring bacteria. Many effectors harbor N-terminal transmembrane domains (TMDs) implicated in effector translocation across target cell membranes. However, the distribution of these TMD-containing effectors remains unknown. Here, we discover prePAAR, a conserved motif found in over 6000 putative TMD-containing effectors encoded predominantly by 15 genera of Proteobacteria. Based on differing numbers of TMDs, effectors group into two distinct classes that both require a member of the Eag family of T6SS chaperones for export. Co-crystal structures of class I and class II effector TMD-chaperone complexes from Salmonella Typhimurium and Pseudomonas aeruginosa, respectively, reveals that Eag chaperones mimic transmembrane helical packing to stabilize effector TMDs. In addition to participating in the chaperone-TMD interface, we find that prePAAR residues mediate effector-VgrG spike interactions. Taken together, our findings reveal mechanisms of chaperone-mediated stabilization and secretion of two distinct families of T6SS membrane protein effectors.

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