The SciZ protein anchors the enteroaggregative <i>Escherichia coli</i> Type VI secretion system to the cell wall

Aschtgen, Marie‐Stéphanie; Gavioli, Marthe; Dessen, Andréa; Lloubès, Roland; Cascales, Éric

doi:10.1111/j.1365-2958.2009.07028.x

Cited by 132 publications

(136 citation statements)

References 52 publications

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“…In enteroaggregative E. coli (EAEC), the T6SS (sciZ) mutant causes a reduction in biofilm formation compared with the wildtype strain (38). In this study, T6SS1 also functioned in regulation of biofilm formation.…”

Section: Figmentioning

confidence: 78%

Two Functional Type VI Secretion Systems in Avian Pathogenic Escherichia coli Are Involved in Different Pathogenic Pathways

Bao

Sun

et al. 2014

Infect Immun

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Type VI secretion systems (T6SSs) are involved in the pathogenicity of several Gram-negative bacteria. The VgrG protein, a core component and effector of T6SS, has been demonstrated to perform diverse functions. The N-terminal domain of VgrG protein is a homologue of tail fiber protein gp27 of phage T4, which performs a receptor binding function and determines the host specificity. Based on sequence analysis, we found that two putative T6SS loci exist in the genome of the avian pathogenic Escherichia coli (APEC) strain TW-XM. To assess the contribution of these two T6SSs to TW-XM pathogenesis, the crucial clpV clusters of these two T6SS loci and their vgrG genes were deleted to generate a series of mutants. Consequently, T6SS1-associated mutants presented diminished adherence to and invasion of several host cell lines cultured in vitro, decreased pathogenicity in duck and mouse infection models in vivo, and decreased biofilm formation and bacterial competitive advantage. In contrast, T6SS2-associated mutants presented a significant decrease only in the adherence to and invasion of mouse brain microvascular endothelial cell (BMEC) line bEnd.3 and brain tissue of the duck infection model. These results suggested that T6SS1 was involved in the proliferation of APEC in systemic infection, whereas VgrG-T6SS2 was responsible only for cerebral infection. Further study demonstrated that VgrG-T6SS2 was able to bind to the surface of bEnd.3 cells, whereas it did not bind to DF-1 (chicken embryo fibroblast) cells, which further proved the interaction of VgrG-T6SS2 with the surface of BMECs.

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Section: Figmentioning

confidence: 78%

Two Functional Type VI Secretion Systems in Avian Pathogenic Escherichia coli Are Involved in Different Pathogenic Pathways

Bao

Sun

et al. 2014

Infect Immun

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“…The induction of the Cpx response changes the expression of a set of genes that are enriched for inner membrane proteins, including a large group of transporter proteins, and also downregulates the production of envelope-spanning protein complexes involved in motility, secretion, and transport (11,32,51). In this light, it is interesting that a number of these complexes depend upon direct interactions with the peptidoglycan for assembly and function (52)(53)(54)(55). These observations may suggest that cell wall alterations could impact the activity and stability of secretion and transport complexes, potentially generating a Cpx-inducing signal.…”

Section: Discussionmentioning

confidence: 99%

The Cpx Envelope Stress Response Modifies Peptidoglycan Cross-Linking via the l,d-Transpeptidase LdtD and the Novel Protein YgaU

Bernal-Cabas¹,

Ayala²,

Raivio³

2014

J. Bacteriol.

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bThe Cpx envelope stress response mediates a complex adaptation to conditions that cause protein misfolding in the periplasm. A recent microarray study demonstrated that Cpx response activation led to changes in the expression of genes known, or predicted, to be involved in cell wall remodeling. We sought to characterize the changes that the cell wall undergoes during activation of the Cpx pathway in Escherichia coli. Luminescent reporters of gene expression confirmed that LdtD, a putative L,D-transpeptidase; YgaU, a protein of unknown function; and Slt, a lytic transglycosylase, are upregulated in response to Cpx-inducing conditions. Phosphorylated CpxR binds to the upstream regions of these genes, which contain putative CpxR binding sites, suggesting that regulation is direct. We show that the activation of the Cpx response causes an increase in the abundance of diaminopimelic acid (DAP)-DAP cross-links that involves LdtD and YgaU. Altogether, our data indicate that changes in peptidoglycan structure are part of the Cpx-mediated adaptation to envelope stress and indicate a role for the uncharacterized gene ygaU in regulating cross-linking. The envelope of Gram-negative bacteria is a complex multilayer structure that protects bacteria from changing conditions in the environment. This structure consists of the outer membrane, the inner membrane, and the periplasmic space. The periplasm contains the cell wall, which provides protection against osmotic stresses and maintains the cell shape. It also provides an oxidizing environment where periplasmic proteins that are translocated from the cytoplasm can be stabilized via disulfide bond formation (1). The periplasm is more sensitive to the conditions outside the cell than the cytoplasm due to the porous nature of the outer membrane (2). Consequently, bacteria have various stress responses whose function consists of sensing and responding to stresses in the periplasm. Among these, the sigma E and Cpx envelope stress responses are thought to respond to conditions that lead to misfolded outer membrane and periplasmic proteins, respectively (3-5, 66). Four additional pathways that respond to envelope stress have been described: the Bae (BaeSR), phage shock (Psp), Rcs, and vesicle release responses. The first three of these pathways have been linked to the efflux of toxic compounds, disruptions of proton motive force, and cell wall perturbations, respectively (6-8).Regulation of the Cpx pathway is carried out by the products of the cpxRA operon that encodes the response regulator CpxR and the histidine kinase CpxA. The Cpx pathway regulates numerous genes for periplasmic protein folding and degrading factors to alleviate envelope stress, including the protease/chaperone DegP, the disulfide oxidase DsbA, and the peptidyl-prolyl isomerase PpiA (9, 10). A recent microarray analysis (11) identified new members of the Cpx regulon by analyzing changes in gene expression after overexpression of NlpE (12), a well-known inducing cue of the Cpx pathway. Some of the novel genes ide...

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“…At the molecular level, the T6SS is assembled from 13 proteins, called core components, that form a transenvelope apparatus anchoring a cytoplasmic tubular structure to the membrane (20)(21)(22)(23)(24). Based on structural homologies with bacteriophage tail components, this tubular structure has been proposed to be constituted of an inner tube assembled by stacked hexameric rings of the Hcp protein, resembling the tail tube of bacteriophages, tipped by the VgrG protein (21,(25)(26)(27).…”

mentioning

confidence: 99%

H-NS Silencing of the Salmonella Pathogenicity Island 6-Encoded Type VI Secretion System Limits Salmonella enterica Serovar Typhimurium Interbacterial Killing

et al. 2015

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The secretion of bacterial toxin proteins is achieved by dedicated machineries called secretion systems. The type VI secretion system (T6SS) is a widespread versatile machine used for the delivery of protein toxins to both prokaryotic and eukaryotic cells. In Salmonella enterica serovar Typhimurium, the expression of the T6SS genes is activated during macrophage or mouse infection. Here, we show that the T6SS gene cluster is silenced by the histone-like nucleoid structuring H-NS protein using a combination of reporter fusions, electrophoretic mobility shift assays, DNase footprinting, and fluorescence microscopy. We further demonstrate that derepression of the S. Typhimurium T6SS genes induces T6SS-dependent intoxication of competing bacteria. Our results suggest that relieving T6SS H-NS silencing may be used as a sense-and-kill mechanism that will help S. Typhimurium to homogenize and synchronize the microbial population to gain efficiency during infection. During the course of infection, bacteria produce and secrete bacterial toxins. Secretion of these toxin proteins is achieved by dedicated, specialized machineries called secretion systems. The type VI secretion system (T6SS) is required for the virulence of several Gram-negative pathogens. In Vibrio cholerae, the T6SS translocates VgrG1, a toxin that carries a domain responsible for actin cross-linking in eukaryotic cells (1-4). However, the role of the T6SS is not limited to virulence toward eukaryotes; an increasing number of reports demonstrate that the T6SS is also involved in interbacterial intoxication (5-10). With bacteriocins and contact-dependent inhibition (CDI), the T6SS is therefore involved in shaping bacterial communities (11-14) by delivering antibacterial toxins, including murein hydrolases, DNases, and phospholipases, directly into the target recipient bacterial cell (5, 6, 15; for recent reviews see references 14, 16 and 17). The attacker cell is protected from these toxins by the coproduction of cognate proteins that confer immunity (15, 18). The T6SS therefore confers a growth advantage to bacteria in mixed cultures and has been suggested to be important in environmental niches where bacterial competition for nutrients is critical for survival or for the uptake of DNA for transformation and acquisition of new traits (14, 19). However, while the role of the T6SS in interbacterial competition has been evidenced and characterized under laboratory conditions, its role in shaping bacterial communities of the microbiota is not yet clearly elucidated.At the molecular level, the T6SS is assembled from 13 proteins, called core components, that form a transenvelope apparatus anchoring a cytoplasmic tubular structure to the membrane (20-24). Based on structural homologies with bacteriophage tail components, this tubular structure has been proposed to be constituted of an inner tube assembled by stacked hexameric rings of the Hcp protein, resembling the tail tube of bacteriophages, tipped by the VgrG protein (21,(25)(26)(27)). The current model descr...

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The SciZ protein anchors the enteroaggregative Escherichia coli Type VI secretion system to the cell wall

Cited by 132 publications

References 52 publications

Two Functional Type VI Secretion Systems in Avian Pathogenic Escherichia coli Are Involved in Different Pathogenic Pathways

Two Functional Type VI Secretion Systems in Avian Pathogenic Escherichia coli Are Involved in Different Pathogenic Pathways

The Cpx Envelope Stress Response Modifies Peptidoglycan Cross-Linking via the l,d-Transpeptidase LdtD and the Novel Protein YgaU

H-NS Silencing of the Salmonella Pathogenicity Island 6-Encoded Type VI Secretion System Limits Salmonella enterica Serovar Typhimurium Interbacterial Killing

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