What is type VI secretion doing in all those bugs? - PubMed (original) (raw)

What is type VI secretion doing in all those bugs?

Sandra Schwarz et al. Trends Microbiol. 2010 Dec.

Abstract

The identification of bacterial secretion systems capable of translocating substrates into eukaryotic cells via needle-like appendages has opened fruitful and exciting areas of microbial pathogenesis research. The recent discovery of the type VI secretion system (T6SS) was met with early speculation that it too acts as a 'needle' that pathogens aim at host cells. New reports demonstrate that certain T6SSs are potent mediators of interbacterial interactions. In light of these findings, we examined earlier data indicating its role in pathogenesis. We conclude that although T6S can, in rare instances, directly influence interactions with higher organisms, the broader physiological significance of the system is likely to provide defense against simple eukaryotic cells and other bacteria in the environment. The crucial role of T6S in bacterial interactions, along with its presence in many organisms relevant to disease, suggests that it might be a key determinant in the progression and outcome of certain human polymicrobial infections.

Copyright © 2010 Elsevier Ltd. All rights reserved.

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Figures

Figure 1

Figure 1

Schematic depiction of bacterial and host cell-targeting T6SS. Asterisks indicate the particular system depicted. Additional representative T6SSs of each specificity are listed and are discussed in detail in the text. The P. aeruginosa H1-T6SS (left) is postulated to target at least three proteins (hexagons) to other bacterial cells [51]. One of these proteins was shown to be a toxin (Tse2), whereas the function(s) of the remaining two is unknown (Tse1 and Tse3). Although cell contact is required for H1-T6SS-dependent targeting of Tse2, the subcellular compartment (e.g. cytosol, periplasm, and outer membrane) to which the Tse proteins are delivered within the recipient cell remains an open question. The V. cholerae vas secretion system (right) functions by translocating an effector domain linked to VgrG into the cytosol of eukaryotic recipient cells [26]. This domain promotes cell rounding by catalyzing the formation of G-actin crosslinks, which are not capable of forming F-actin [78].

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