Article

Type VI secretion requires a dynamic contractile phage tail-like structure

Department of Microbiology and Immunobiology, Harvard Medical School, 200 Longwood Avenue, Boston, Massachusetts 02115, USA.
Nature (Impact Factor: 42.35). 03/2012; 483(7388):182-6. DOI: 10.1038/nature10846
Source: PubMed

ABSTRACT Type VI secretion systems are bacterial virulence-associated nanomachines composed of proteins that are evolutionarily related to components of bacteriophage tails. Here we show that protein secretion by the type VI secretion system of Vibrio cholerae requires the action of a dynamic intracellular tubular structure that is structurally and functionally homologous to contractile phage tail sheath. Time-lapse fluorescence light microscopy reveals that sheaths of the type VI secretion system cycle between assembly, quick contraction, disassembly and re-assembly. Whole-cell electron cryotomography further shows that the sheaths appear as long tubular structures in either extended or contracted conformations that are connected to the inner membrane by a distinct basal structure. These data support a model in which the contraction of the type VI secretion system sheath provides the energy needed to translocate proteins out of effector cells and into adjacent target cells.

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    • "The appearance of Stacks in the tomogram slices bore a resemblance to the structure of the type 6 secretion system (T6SS). T6SS forms highly dynamic intracellular tubes, which assemble and disassemble in a few seconds at different subcellular locations (Chang et al., 2014; Basler et al., 2012). Moreover, both structures, Stacks and T6SS, are oriented roughly perpendicular to the PM and are located exclusively in the cytosol. "
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    • "High sequence similarities and striking structural parallels between the phage tail structures and bacterial pyocins reveal a clear evolutionary connection between these complex molecular devices (Nakayama et al., 2000). Another phage-like structure found in bacteria including P. aeruginosa is a dynamic bacterial type VI secretion system (T6SS) used for translocation of virulence factors into target cells: the same mechanism the phage uses to transfer its genome to the host (Basler et al., 2012). Moreover, a recent report has shown that phage tail-like structures produced by marine bacterium Pseudoalteromonas luteoviolacea can trigger metamorphosis of a marine tubeworm, providing novel insights into the intricate interaction between phage, bacterium and animal (Shikuma et al., 2014). "
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    • "Since the toxin is encoded in the genome of the prophage and is not part of the host genome, non-lysogenic cells do not cause cholera (Weinbauer, 2004). In addition, it was recently shown that the type VI secretion systems in V. cholerae are virulence-associated proteins that are evolutionarily related to components of bacteriophage tails (Basler et al., 2012). Prophage induction events can change the bacterial community structure by increasing the diversity and richness of natural bacterial populations (Hewson and Fuhrman, 2007). "
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