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The Vibrio cholerae type VI secretion system displays antimicrobial properties
Dana L MacIntyre1, Sarah T Miyata, Maya Kitaoka
1Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB, Canada T6G 2H7.
Summary
Vibrio cholerae uses a type VI secretion system (T6SS) to kill other bacteria, not just host cells. This bacterial competition mechanism may help cholera bacteria survive in aquatic environments.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Cholera is an acute diarrheal disease caused by Vibrio cholerae.
- A type VI secretion system (T6SS) is present in V. cholerae and contributes to virulence against eukaryotic cells.
- The T6SS is structurally similar to a bacteriophage cell-puncturing device.
Purpose of the Study:
- To investigate the interbacterial virulence of Vibrio cholerae.
- To determine the role of the type VI secretion system (T6SS) in V. cholerae's interactions with other bacteria.
- To explore the potential role of T6SS in environmental survival and interspecies competition.
Main Methods:
- Testing the virulence of V. cholerae strain V52 (O37 serogroup, constitutively active T6SS) against Gram-negative bacteria like E. coli and Salmonella Typhimurium.
- Utilizing T6SS-deficient mutants (V52ΔvasK, V52ΔvasH) to confirm the T6SS-dependent toxicity.
- Assessing the resistance of V. cholerae strains (including O1 serogroup) to V52.
Main Results:
- V. cholerae strain V52 demonstrated high virulence against E. coli and S. Typhimurium, reducing E. coli survival by up to 100,000-fold.
- Toxicity was dependent on a functional T6SS, as T6SS-deficient mutants showed defects that could be complemented.
- V. cholerae V52 and O1 serogroup strains exhibited resistance to V52, indicating acquired immunity independent of serogroup.
Conclusions:
- The V. cholerae T6SS confers toxicity against other bacteria, in addition to eukaryotic host cells.
- This interbacterial virulence likely functions as a mechanism for interspecies competition, enhancing environmental survival.
- The T6SS may play a crucial role in V. cholerae's survival in aquatic ecosystems during cholera transmission and inter-epidemic periods.
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