Bioinformatic Analysis of the Campylobacter jejuni Type VI Secretion System and Effector Prediction

The Type VI Secretion System (T6SS) has important roles relating to bacterial antagonism, subversion of host cells, and niche colonisation. Campylobacter jejuni is one of the leading bacterial causes of human gastroenteritis worldwide and is a commensal coloniser of birds. Although recently discovered, the T6SS biological functions and identities of its effectors are still poorly defined in C. jejuni. Here, we perform a comprehensive bioinformatic analysis of the C. jejuni T6SS by investigating the prevalence and genetic architecture of the T6SS in 513 publicly available genomes using C. jejuni 488 strain as reference. A unique and conserved T6SS cluster associated with the Campylobacter jejuni Integrated Element 3 (CJIE3) was identified in the genomes of 117 strains. Analyses of the T6SS-positive 488 strain against the T6SS-negative C. jejuni RM1221 strain and the T6SS-positive plasmid pCJDM202 carried by C. jejuni WP2-202 strain defined the “T6SS-containing CJIE3” as a pathogenicity island, thus renamed as Campylobacter jejuni Pathogenicity Island-1 (CJPI-1). Analysis of CJPI-1 revealed two canonical VgrG homologues, CJ488_0978 and CJ488_0998, harbouring distinct C-termini in a genetically variable region downstream of the T6SS operon. CJPI-1 was also found to carry a putative DinJ-YafQ Type II toxin-antitoxin (TA) module, conserved across pCJDM202 and the genomic island CJIE3, as well as several open reading frames functionally predicted to encode for nucleases, lipases, and peptidoglycan hydrolases. This comprehensive in silico study provides a framework for experimental characterisation of T6SS-related effectors and TA modules in C. jejuni.

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The Type VI Secretion System Encoded in Salmonella Pathogenicity Island 19 Is Required for Salmonella enterica Serotype Gallinarum Survival within Infected Macrophages

Infection and Immunity ◽

10.1128/iai.01165-12 ◽

2013 ◽

Vol 81 (4) ◽

pp. 1207-1220 ◽

Cited By ~ 36

Author(s):

Carlos J. Blondel ◽

Juan C. Jiménez ◽

Lorenzo E. Leiva ◽

Sergio A. Álvarez ◽

Bernardo I. Pinto ◽

...

Keyword(s):

Salmonella Enterica ◽

Pathogenicity Island ◽

Secretion System ◽

Host Cells ◽

Economic Losses ◽

Type Vi Secretion System ◽

Content Type ◽

Type Vi Secretion ◽

Core Components

ABSTRACTSalmonella entericaserotype Gallinarum is the causative agent of fowl typhoid, a disease characterized by high morbidity and mortality that causes major economic losses in poultry production. We have reported thatS. Gallinarum harbors a type VI secretion system (T6SS) encoded inSalmonellapathogenicity island 19 (SPI-19) that is required for efficient colonization of chicks. In the present study, we aimed to characterize the SPI-19 T6SS functionality and to investigate the mechanisms behind the phenotypes previously observedin vivo. Expression analyses revealed that SPI-19 T6SS core components are expressed and produced underin vitrobacterial growth conditions. However, secretion of the structural/secreted components Hcp1, Hcp2, and VgrG to the culture medium could not be determined, suggesting that additional signals are required for T6SS-dependent secretion of these proteins.In vitrobacterial competition assays failed to demonstrate a role for SPI-19 T6SS in interbacterial killing. In contrast, cell culture experiments with murine and avian macrophages (RAW264.7 and HD11, respectively) revealed production of a green fluorescent protein-tagged version of VgrG soon afterSalmonellauptake. Furthermore, infection of RAW264.7 and HD11 macrophages with deletion mutants of SPI-19 or strains with genes encoding specific T6SS core components (clpVandvgrG) revealed that SPI-19 T6SS contributes toS. Gallinarum survival within macrophages at 20 h postuptake. SPI-19 T6SS function was not linked toSalmonella-induced cytotoxicity or cell death of infected macrophages, as has been described for other T6SS. Our data indicate that SPI-19 T6SS corresponds to a novel tool used bySalmonellato survive within host cells.

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Corrigendum: Bioinformatic Analysis of the Campylobacter jejuni Type VI Secretion System and Effector Prediction

Frontiers in Microbiology ◽

10.3389/fmicb.2021.793252 ◽

2021 ◽

Vol 12 ◽

Author(s):

Luca Robinson ◽

Janie Liaw ◽

Zahra Omole ◽

Dong Xia ◽

Arnoud H. M. van Vliet ◽

...

Keyword(s):

Campylobacter Jejuni ◽

Bioinformatic Analysis ◽

Secretion System ◽

Type Vi Secretion System ◽

Type Vi Secretion

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The Type VI Secretion System Modulates Flagellar Gene Expression and Secretion in Citrobacter freundii and Contributes to Adhesion and Cytotoxicity to Host Cells

Infection and Immunity ◽

10.1128/iai.03071-14 ◽

2015 ◽

Vol 83 (7) ◽

pp. 2596-2604 ◽

Cited By ~ 20

Author(s):

Liyun Liu ◽

Shuai Hao ◽

Ruiting Lan ◽

Guangxia Wang ◽

Di Xiao ◽

...

Keyword(s):

Secretion System ◽

Host Cells ◽

Target Cells ◽

Deletion Mutants ◽

Citrobacter Freundii ◽

Wild Type ◽

Type Vi Secretion System ◽

Content Type ◽

Type Vi Secretion ◽

Mutant Strains

The type VI secretion system (T6SS) as a virulence factor-releasing system contributes to virulence development of various pathogens and is often activated upon contact with target cells.Citrobacter freundiistrain CF74 has a complete T6SS genomic island (GI) that containsclpV,hcp-2, andvgrT6SS genes. We constructedclpV,hcp-2,vgr, and T6SS GI deletion mutants in CF74 and analyzed their effects on the transcriptome overall and, specifically, on the flagellar system at the levels of transcription and translation. Deletion of the T6SS GI affected the transcription of 84 genes, with 15 and 69 genes exhibiting higher and lower levels of transcription, respectively. Members of the cell motility class of downregulated genes of the CF74ΔT6SS mutant were mainly flagellar genes, including effector proteins, chaperones, and regulators. Moreover, the production and secretion of FliC were also decreased inclpV,hcp-2,vgr, or T6SS GI deletion mutants in CF74 and were restored upon complementation. In swimming motility assays, the mutant strains were found to be less motile than the wild type, and motility was restored by complementation. The mutant strains were defective in adhesion to HEp-2 cells and were restored partially upon complementation. Further, the CF74ΔT6SS, CF74ΔclpV, and CF74Δhcp-2mutants induced lower cytotoxicity to HEp-2 cells than the wild type. These results suggested that the T6SS GI in CF74 regulates the flagellar system, enhances motility, is involved in adherence to host cells, and induces cytotoxicity to host cells. Thus, the T6SS plays a wide-ranging role inC. freundii.

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Molecular characterization of megaplasmids encoding the type VI secretion system in Campylobacter jejuni isolated from chicken livers and gizzards

Scientific Reports ◽

10.1038/s41598-020-69155-z ◽

2020 ◽

Vol 10 (1) ◽

Cited By ~ 1

Author(s):

Daya Marasini ◽

Anand B. Karki ◽

John M. Bryant ◽

Robert J. Sheaff ◽

Mohamed K. Fakhr

Keyword(s):

Molecular Characterization ◽

Campylobacter Jejuni ◽

Secretion System ◽

Type Vi Secretion System ◽

Type Vi Secretion

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The Campylobacter jejuni Type VI Secretion System Enhances the Oxidative Stress Response and Host Colonization

Frontiers in Microbiology ◽

10.3389/fmicb.2019.02864 ◽

2019 ◽

Vol 10 ◽

Cited By ~ 6

Author(s):

Janie Liaw ◽

Geunhye Hong ◽

Cadi Davies ◽

Abdi Elmi ◽

Filip Sima ◽

...

Keyword(s):

Oxidative Stress ◽

Stress Response ◽

Campylobacter Jejuni ◽

Oxidative Stress Response ◽

Secretion System ◽

Type Vi Secretion System ◽

Host Colonization ◽

Type Vi Secretion

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

Journal of Bacteriology ◽

10.1128/jb.00198-08 ◽

2008 ◽

Vol 190 (13) ◽

pp. 4584-4595 ◽

Cited By ~ 85

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.

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VgrG-dependent effectors and chaperones modulate the assembly of the type VI secretion system

PLoS Pathogens ◽

10.1371/journal.ppat.1010116 ◽

2021 ◽

Vol 17 (12) ◽

pp. e1010116

Author(s):

Xiaoye Liang ◽

Tong-Tong Pei ◽

Hao Li ◽

Hao-Yu Zheng ◽

Han Luo ◽

...

Keyword(s):

Secretion System ◽

Effector Proteins ◽

Host Cells ◽

Structural Proteins ◽

Wild Type ◽

Type Vi Secretion System ◽

Double Deletion ◽

Type Vi Secretion ◽

Structural Determinant

The type VI secretion system (T6SS) is a spear-like nanomachine found in gram-negative pathogens for delivery of toxic effectors to neighboring bacterial and host cells. Its assembly requires a tip spike complex consisting of a VgrG-trimer, a PAAR protein, and the interacting effectors. However, how the spike controls T6SS assembly remains elusive. Here we investigated the role of three VgrG-effector pairs in Aeromonas dhakensis strain SSU, a clinical isolate with a constitutively active T6SS. By swapping VgrG tail sequences, we demonstrate that the C-terminal ~30 amino-acid tail dictates effector specificity. Double deletion of vgrG1&2 genes (VgrG3+) abolished T6SS secretion, which can be rescued by ectopically expressing chimeric VgrG3 with a VgrG1/2-tail but not the wild type VgrG3. In addition, deletion of effector-specific chaperones also severely impaired T6SS secretion, despite the presence of intact VgrG and effector proteins, in both SSU and Vibrio cholerae V52. We further show that SSU could deliver a V. cholerae effector VasX when expressing a plasmid-borne chimeric VgrG with VasX-specific VgrG tail and chaperone sequences. Pull-down analyses show that two SSU effectors, TseP and TseC, could interact with their cognate VgrGs, the baseplate protein TssK, and the key assembly chaperone TssA. Effectors TseL and VasX could interact with TssF, TssK and TssA in V. cholerae. Collectively, we demonstrate that chimeric VgrG-effector pairs could bypass the requirement of heterologous VgrG complex and propose that effector-stuffing inside the baseplate complex, facilitated by chaperones and the interaction with structural proteins, serves as a crucial structural determinant for T6SS assembly.

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The structure of VgrG1 fromPseudomonas aeruginosa, the needle tip of the bacterial type VI secretion system

Acta Crystallographica Section D Structural Biology ◽

10.1107/s2059798315021142 ◽

2016 ◽

Vol 72 (1) ◽

pp. 22-33 ◽

Cited By ~ 23

Author(s):

Mercedes Spínola-Amilibia ◽

Irene Davó-Siguero ◽

Federico M. Ruiz ◽

Elena Santillana ◽

Francisco Javier Medrano ◽

...

Keyword(s):

Pathogenic Bacteria ◽

Neck Region ◽

Structural Features ◽

Secretion System ◽

Host Cells ◽

Type Vi Secretion System ◽

Competitive Environments ◽

Type Vi Secretion ◽

Target Membrane ◽

T4 Phage

The type VI secretion system (T6SS) is a mechanism that is commonly used by pathogenic bacteria to infect host cells and for survival in competitive environments. This system assembles on a core baseplate and elongates like a phage puncturing device; it is thought to penetrate the target membrane and deliver effectors into the host or competing bacteria. Valine–glycine repeat protein G1 (VgrG1) forms the spike at the tip of the elongating tube formed by haemolysin co-regulated protein 1 (Hcp1); it is structurally similar to the T4 phage (gp27)3–(gp5)3puncturing complex. Here, the crystal structure of full-length VgrG1 fromPseudomonas aeruginosais reported at a resolution of 2.0 Å, which through a trimeric arrangement generates a needle-like shape composed of two main parts, the head and the spike, connectedviaa small neck region. The structure reveals several remarkable structural features pointing to the possible roles of the two main segments of VgrG1: the head as a scaffold cargo domain and the β-roll spike with implications in the cell-membrane puncturing process and as a carrier of cognate toxins.

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