Pleiotropic effects of the twin-arginine translocation system on biofilm formation, colonization, and virulence in Vibrio cholerae

State Key Laboratory for Infectious Disease Prevention and Control, Department of Diarrheal Diseases, Chinese Center for Disease Control and Prevention, Beijing, PR China.
BMC Microbiology (Impact Factor: 2.73). 02/2009; 9(1):114. DOI: 10.1186/1471-2180-9-114
Source: PubMed


The Twin-arginine translocation (Tat) system serves to translocate folded proteins, including periplasmic enzymes that bind redox cofactors in bacteria. The Tat system is also a determinant of virulence in some pathogenic bacteria, related to pleiotropic effects including growth, motility, and the secretion of some virulent factors. The contribution of the Tat pathway to Vibrio cholerae has not been explored. Here we investigated the functionality of the Tat system in V. cholerae, the etiologic agent of cholera.
In V. cholerae, the tatABC genes function in the translocation of TMAO reductase. Deletion of the tatABC genes led to a significant decrease in biofilm formation, the ability to attach to HT-29 cells, and the ability to colonize suckling mouse intestines. In addition, we observed a reduction in the output of cholera toxin, which may be due to the decreased transcription level of the toxin gene in tatABC mutants, suggesting an indirect effect of the mutation on toxin production. No obvious differences in flagellum biosynthesis and motility were found between the tatABC mutant and the parental strain, showing a variable effect of Tat in different bacteria.
The Tat system contributes to the survival of V. cholerae in the environment and in vivo, and it may be associated with its virulence.

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    • "The Tat system was observed to be involved in cell adherence and intracellular survival in various eukaryotic cell lines in E. tarda (Table 1). Tat mutants in other pathogenic bacteria such as V. cholerae (Zhang et al., 2009), Legionella pneumophila (DeBuck et al., 2005) and Salmonella enterica (Reynolds et al., 2011) also associate or replicate poorly in eukaryotic cells. In S. enterica, the reduced infection of cultured macrophages by the Tat mutants may represent a difficulty phagocytosing which is caused by the chain-forming phenotype of the Tat mutants that were not easily*Spot no. was consistent with the number in Fig. 2aand b. "
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    ABSTRACT: Edwardsiella tarda is a Gram-negative, facultative aerobic pathogen which infects multifarious hosts including fish, amphibians, and human beings. A twin-arginine translocation (Tat) gene cluster important for high-salt tolerance in E. tarda was previously identified. Here the genetic structure and pleiotropic roles of the Tat system in physiological adaptation of the bacterium were further characterized. Functional analysis indicated that tatD was not required for Tat export process and tatE might be an allelic gene of tatA in the bacterium. The results showed that disruption in Tat system did not affect morphology and biofilm formation in E. tarda, but affected motility, hemagglutination, cell aggregation and infection of eukaryotic cells (e.g., macrophage J774a). Comparative proteomics analysis of subcellular proteins using two-dimensional gel electrophoresis and a qualitative shotgun protein sequencing method were implemented to identify proteins differentially expressed in E. tarda EIB202 vs. ∆tatABCD. The results revealed a large repertoire of differentially expressed proteins (n=61), sheding light on Tat system associated with the virulence and stress-associated processes in E. tarda. © 2013 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.
    Full-text · Article · Mar 2013 · FEMS Microbiology Letters
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    • "All protein synthesis takes place in the cytoplasm, so all non-cytoplasmic proteins must pass through one or two lipid bilayers by a mechanism commonly called "secretion". Protein secretion is involved in various processes including plant-microbe interactions [4,5]), biofilm formation [6,7] and virulence of plant and human pathogens [8-10]. Two main systems are involved in protein translocation across the cytoplasmic membrane, namely the essential and universal Sec (Secretion) pathway and the Tat (Twin-arginine translocation) pathway found in some prokaryotes (monoderms and diderms) and eukaryotes alike [11-16]. "
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    ABSTRACT: The twin-arginine translocase (Tat) provides protein export in bacteria and plant chloroplasts and is capable of transporting fully folded proteins across the membrane. We resolved the conformation and membrane alignment of the pore-forming subunit TatA(d) from Bacillus subtilis using solid-state NMR spectroscopy. The relevant structured part of the protein, TatA(2-45), contains a transmembrane segment (TMS) and an amphiphilic helix (APH). It was reconstituted in planar bicelles, which represent the lipid environment of a bacterial membrane. The SAMMY solid-state NMR experiment was used to correlate (15)N chemical shifts and (1)H-(15)N dipolar couplings in the backbone and side chains of the (15)N-labeled protein. The observed wheel-like patterns ("PISA wheels") in the resulting 2-dimensional spectra confirm the α-helical character of the two segments and reveal their alignment in the lipid bilayer. Helix tilt angles (τ(TMS) = 13°, τ(APH) = 64°) were obtained from uniformly labeled protein, and azimuthal rotations (ρ(Val15) = 235°, ρ(Ile29) = 25°) were obtained from selective labels. These constraints define two distinct families of allowed structures for TatA in the membrane-bound state. The manifold of solutions could be narrowed down to a unique structure by using input from a liquid-state NMR study of TatA in detergent micelles, as recently described [Hu, Y.; Zhao, E.; Li, H.; Xia, B.; Jin, C. J. Am. Chem. Soc. 2010, DOI: 10.1021/ja1053785]. Interestingly, the APH showed an unexpectedly slanted alignment in the protein, different from that of the isolated APH peptide. This finding implies that the amphiphilic region of TatA is not just a flexible attachment to the transmembrane anchor but might be able to form intra- or even intermolecular salt-bridges, which could play a key role in pore assembly.
    No preview · Article · Oct 2010 · Journal of the American Chemical Society
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