Bacterium found to hunt for fresh DNA, killing for 150 genes on average

Details of the cholera bacterium’s T6SS (type VI secretion system) have been worked out with sequencing methods – and showed the unexpected breadth of horizontal gene transfer.

Bacteria are known to pick up DNA present in the environment. It is still one of the main methods of genetic engineering. Evolution promoted this ability to increase the pace of adaptations, allowing for quick exchange of essential genes, such as those for antibiotic resistance.

A simple collection of surrounding DNA is only part of the story. In the last years, scientists have discovered more aggressive strategies, which utilize toxins and sophisticated mechanisms. One of them, fascinating T6SS is present in Vibrio cholerae. The cholera bacterium actively looks for other bacteria and targets them with a contractable protein-built spike. After the prey is pierced, various toxins are injected, causing the death of the targeted single-celled organism. Then, V. cholerae feasts on the remains, picking up fresh DNA.

A team from EPFL analyzed details of those microbiological hunts. 360 organisms were sequenced near the T6SS event. Comparisons showed that even 150,000 base pairs of DNA were changed – an equivalent of 150 bacterial genes.

The results will have implications for counteractions to bacterial resistance. They also expand the growing volume of evidence behind the surprisingly significant role of horizontal gene transfer in the evolution of bacteria.

Publication: Matthey, N., Stutzmann, S., Stoudmann, C., Guex, N., Iseli, C., & Blokesch, M. (2019). Neighbor predation linked to natural competence fosters the transfer of large genomic regions in Vibrio cholerae. Doi:10.7554/eLife.48212.001
Photo: https://www.youtube.com/watch?v=Xk7rxv6HtKo

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