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Proc Natl Acad Sci U S A. 2018 Jul 31;115(31):7997-8002. doi: 10.1073/pnas.1808469115. Epub 2018 Jul 18.

Exopolysaccharide protects Vibrio cholerae from exogenous attacks by the type 6 secretion system.

Author information

1
Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115.
2
Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115 john_mekalanos@hms.harvard.edu.

Abstract

The type 6 secretion system (T6SS) is a nanomachine used by many Gram-negative bacteria, including Vibrio cholerae, to deliver toxic effector proteins into adjacent eukaryotic and bacterial cells. Because the activity of the T6SS is dependent on direct contact between cells, its activity is limited to bacteria growing on solid surfaces or in biofilms. V. cholerae can produce an exopolysaccharide (EPS) matrix that plays a role in adhesion and biofilm formation. In this work, we investigated the effect of EPS production on T6SS activity between cells. We found that EPS produced by V. cholerae cells functions as a unidirectional protective armor that blocks exogenous T6SS attacks without interfering with its own T6SS functionality. This EPS armor is effective against both same-species and heterologous attackers. Mutations modulating the level of EPS biosynthesis gene expression result in corresponding modulation in V. cholerae resistance to exogenous T6SS attack. These results provide insight into the potential role of extracellular biopolymers, including polysaccharides, capsules, and S-layers in protecting bacterial cells from attacks involving cell-associated macromolecular protein machines that cannot readily diffuse through these mechanical defenses.

KEYWORDS:

antibacterials; capsule; commensal; microbiota; secretion

PMID:
30021850
PMCID:
PMC6077691
DOI:
10.1073/pnas.1808469115
[Indexed for MEDLINE]
Free PMC Article

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