scholarly journals In vivo structures of an intact type VI secretion system revealed by electron cryotomography

EMBO Reports ◽  
2017 ◽  
Vol 18 (7) ◽  
pp. 1090-1099 ◽  
Author(s):  
Yi‐Wei Chang ◽  
Lee A Rettberg ◽  
Davi R Ortega ◽  
Grant J Jensen
Keyword(s):  
Secretion System ◽  
Type Vi Secretion System ◽  
Type Vi Secretion ◽  
Electron Cryotomography

scholarly journals In vivo structures of an intact type VI secretion system revealed by electron cryotomography

2017 ◽  
Author(s):  
Yi-Wei Chang ◽  
Lee A. Rettberg ◽  
Grant J. Jensen
Keyword(s):  
Structural Information ◽  
Cell Envelope ◽  
Secretion System ◽  
Tail Fiber ◽  
Type Vi Secretion System ◽  
Membrane Complex ◽  
Type Vi Secretion ◽  
Electron Cryotomography ◽  
Structural Insights

SUMMARYThe type VI secretion system (T6SS) is a versatile molecular weapon used by many bacteria against eukaryotic hosts or prokaryotic competitors. It consists of a cytoplasmic bacteriophage tail-like structure anchored in the bacterial cell envelope via a cytoplasmic baseplate and a periplasmic membrane complex. Rapid contraction of the sheath in the bacteriophage tail-like structure propels an inner tube/spike complex through the target cell envelope to deliver effectors. While structures of purified contracted sheath and purified membrane complex have been solved, because sheaths contract upon cell lysis and purification, no structure is available for the extended sheath. Structural information about the baseplate is also lacking. Here we use electron cryotomography to directly visualize intact T6SS structures inside Myxococcus xanthus cells. Using sub-tomogram averaging, we resolve the structure of the extended sheath and membrane-associated components including the baseplate. Moreover, we identify novel extracellular bacteriophage tail fiber-like antennae. These results provide new structural insights into how the extended sheath prevents premature disassembly and how this sophisticated machine may recognize targets.

Citrobacter freundii Activation of NLRP3 Inflammasome via the Type VI Secretion System

2020 ◽  
Author(s):  
Liyun Liu ◽  
Liqiong Song ◽  
Rong Deng ◽  
Ruiting Lan ◽  
Wenjie Jin ◽  
...  
Keyword(s):  
Nlrp3 Inflammasome ◽  
Secretion System ◽  
Interleukin 1Β ◽  
Inflammasome Activation ◽  
Dependent Manner ◽  
Citrobacter Freundii ◽  
Type Vi Secretion System ◽  
Type Vi Secretion ◽  
Tract Infections

Abstract Citrobacter freundii is a significant cause of human infections, responsible for food poisoning, diarrhea, and urinary tract infections. We previously identified a highly cytotoxic and adhesive C. freundii strain CF74 expressing a type VI secretion system (T6SS). In this study, we showed that in mice-derived macrophages, C. freundii CF74 activated the Nucleotide Oligomerization Domain -Like Receptor Family, Pyrin Domain Containing 3(NLRP3) inflammasomes in a T6SS-dependent manner. The C. freundii T6SS activated the inflammasomes mainly through caspase 1 and mediated pyroptosis of macrophages by releasing the cleaved gasdermin-N domain. The CF74 T6SS was required for flagellin-induced interleukin 1β release by macrophages. We further show that the T6SS tail component and effector, hemolysin co-regulation protein-2 (Hcp-2), was necessary and sufficient to trigger NLRP3 inflammasome activation. In vivo, the T6SS played a key role in mediating interleukin 1β secretion and the survival of mice during C. freundii infection in mice. These findings provide novel insights into the role of T6SS in the pathogenesis of C. freundii.

scholarly journals Temperature and growth phase influence the outer-membrane proteome and the expression of a type VI secretion system in Yersinia pestis

Microbiology ◽  
2009 ◽  
Vol 155 (2) ◽  
pp. 498-512 ◽  
Author(s):  
Rembert Pieper ◽  
Shih-Ting Huang ◽  
Jeffrey M. Robinson ◽  
David J. Clark ◽  
Hamid Alami ◽  
...  
Keyword(s):  
Yersinia Pestis ◽  
Outer Membrane ◽  
Subcellular Fractionation ◽  
Secretion System ◽  
Dependent Manner ◽  
Type Vi Secretion System ◽  
Extracellular Medium ◽  
Type Vi Secretion

Yersinia pestis cells were grown in vitro at 26 and 37 °C, the ambient temperatures of its flea vector and its mammalian hosts, respectively, and subjected to subcellular fractionation. Abundance changes at 26 vs 37 °C were observed for many outer-membrane (OM) proteins. The cell adhesion protein Ail (y1324) and three putative small β-barrel OM proteins (y1795, y2167 and y4083) were strongly increased at 37 °C. The Ail/Lom family protein y1682 (OmpX) was strongly increased at 26 °C. Several porins and TonB-dependent receptors, which control small molecule transport through the OM, were also altered in abundance in a temperature-dependent manner. These marked differences in the composition of the OM proteome are probably important for the adaptation of Y. pestis to its in vivo life stages. Thirteen proteins that appear to be part of an intact type VI secretion system (T6SS) were identified in membrane fractions of stationary-phase cells grown at 26 °C, but not at 37 °C. The corresponding genes are clustered in the Y. pestis KIM gene locus y3658–y3677. The proteins y3674 and y3675 were particularly abundant and co-fractionated in a M r range indicative of participation in a multi-subunit complex. The soluble haemolysin-coregulated protein y3673 was even more abundant. Its release into the extracellular medium was triggered by treatment of Y. pestis cells with trypsin. Proteases and other stress-response-inducing factors may constitute environmental cues resulting in the activation of the T6SS in Y. pestis.

scholarly journals Incompatibility of Vibrio fischeri Strains during Symbiosis Establishment Depends on Two Functionally Redundant hcp Genes

2019 ◽  
Vol 201 (19) ◽  
Author(s):  
Kirsten R. Guckes ◽  
Andrew G. Cecere ◽  
Nathan P. Wasilko ◽  
Amanda L. Williams ◽  
Katherine M. Bultman ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Genetic Factors ◽  
Vibrio Fischeri ◽  
Secretion System ◽  
Light Organ ◽  
Type Vi Secretion System ◽  
Content Type ◽  
Type Vi Secretion ◽  
Different Strains

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.

scholarly journals Campylobacter jejuni Type VI Secretion System: Roles in Adaptation to Deoxycholic Acid, Host Cell Adherence, Invasion, and In Vivo Colonization

PLoS ONE ◽  
2012 ◽  
Vol 7 (8) ◽  
pp. e42842 ◽  
Author(s):  
Kvin Lertpiriyapong ◽  
Eric R. Gamazon ◽  
Yan Feng ◽  
Danny S. Park ◽  
Jassia Pang ◽  
...  
Keyword(s):  
Host Cell ◽  
Campylobacter Jejuni ◽  
Deoxycholic Acid ◽  
Secretion System ◽  
Type Vi Secretion System ◽  
Cell Adherence ◽  
Type Vi Secretion

scholarly journals N-Acylhomoserine lactones involved in quorum sensing control the type VI secretion system, biofilm formation, protease production, and in vivo virulence in a clinical isolate of Aeromonas hydrophila

Microbiology ◽  
2009 ◽  
Vol 155 (11) ◽  
pp. 3518-3531 ◽  
Author(s):  
Bijay K. Khajanchi ◽  
Jian Sha ◽  
Elena V. Kozlova ◽  
Tatiana E. Erova ◽  
Giovanni Suarez ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Aeromonas Hydrophila ◽  
Biofilm Formation ◽  
Secretion System ◽  
Protease Production ◽  
Type Vi Secretion System ◽  
Double Knockout ◽  
Electron Microscopic ◽  
Type Vi Secretion

In this study, we delineated the role of N-acylhomoserine lactone(s) (AHLs)-mediated quorum sensing (QS) in the virulence of diarrhoeal isolate SSU of Aeromonas hydrophila by generating a double knockout ΔahyRI mutant. Protease production was substantially reduced in the ΔahyRI mutant when compared with that in the wild-type (WT) strain. Importantly, based on Western blot analysis, the ΔahyRI mutant was unable to secrete type VI secretion system (T6SS)-associated effectors, namely haemolysin coregulated protein and the valine-glycine repeat family of proteins, while significant levels of these effectors were detected in the culture supernatant of the WT A. hydrophila. In contrast, the production and translocation of the type III secretion system (T3SS) effector AexU in human colonic epithelial cells were not affected when the ahyRI genes were deleted. Solid surface-associated biofilm formation was significantly reduced in the ΔahyRI mutant when compared with that in the WT strain, as determined by a crystal violet staining assay. Scanning electron microscopic observations revealed that the ΔahyRI mutant was also defective in the formation of structured biofilm, as it was less filamentous and produced a distinct exopolysaccharide on its surface when compared with the structured biofilm produced by the WT strain. These effects of AhyRI could be complemented either by expressing the ahyRI genes in trans or by the exogeneous addition of AHLs to the ΔahyRI/ahyR+ complemented strain. In a mouse lethality experiment, 50 % attenuation was observed when we deleted the ahyRI genes from the parental strain of A. hydrophila. Together, our data suggest that AHL-mediated QS modulates the virulence of A. hydrophila SSU by regulating the T6SS, metalloprotease production and biofilm formation.

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