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PLoS Comput Biol. 2015 Oct 20;11(10):e1004520. doi: 10.1371/journal.pcbi.1004520. eCollection 2015 Oct.

Established Microbial Colonies Can Survive Type VI Secretion Assault.

Author information

1
Princeton University, Lewis-Sigler Institute for Integrative Genomics, Princeton, New Jersey, United States of America.
2
Universität Basel, Biozentrum, Basel, Switzerland.
3
Princeton University, Lewis-Sigler Institute for Integrative Genomics, Princeton, New Jersey, United States of America; Princeton University, Department of Molecular Biology, Princeton, New Jersey, United States of America.

Abstract

Type VI secretion (T6S) is a cell-to-cell injection system that can be used as a microbial weapon. T6S kills vulnerable cells, and is present in close to 25% of sequenced Gram-negative bacteria. To examine the ecological role of T6S among bacteria, we competed self-immune T6S+ cells and T6S-sensitive cells in simulated range expansions. As killing takes place only at the interface between sensitive and T6S+ strains, while growth takes place everywhere, sufficiently large domains of sensitive cells can achieve net growth in the face of attack. Indeed T6S-sensitive cells can often outgrow their T6S+ competitors. We validated these findings through in vivo competition experiments between T6S+ Vibrio cholerae and T6S-sensitive Escherichia coli. We found that E. coli can survive and even dominate so long as they have an adequate opportunity to form microcolonies at the outset of the competition. Finally, in simulated competitions between two equivalent and mutually sensitive T6S+ strains, the more numerous strain has an advantage that increases with the T6S attack rate. We conclude that sufficiently large domains of T6S-sensitive individuals can survive attack and potentially outcompete self-immune T6S+ bacteria.

PMID:
26485125
PMCID:
PMC4619000
DOI:
10.1371/journal.pcbi.1004520
[Indexed for MEDLINE]
Free PMC Article

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