Cholera Bacteria Use “Spears” to Kill Other Bacteria to Reduce Competition and Promote Horizontal Gene Transfer

Cholera is caused when the bacterium Vibrio cholerae infects the small intestine. The disease is characterized by acute watery diarrhea resulting in severe dehydration. EPFL (École Polytechnique Fédérale de Lausanne ) scientists in Switzerland have now demonstrated that V. cholerae uses a tiny spear to stab and kill neighboring bacteria - even of its own kind - and then steal their DNA. This mechanism, known as "horizontal gene transfer," allows the cholera bacterium to become more virulent by absorbing the traits of its prey. The study is published in the January 2, 2015 issue of Science. The laboratory of Dr. Melanie Blokesch at EPFL has uncovered how V. cholerae uses a predatory killing device to compete with surrounding bacteria and steal their DNA. This molecular killing device is essentially a spring-loaded spear that is constantly shooting out. This weapon is called the "type VI secretion system" (T6SS) and is known to exist in many types of bacteria. When V. cholerae comes close to other bacteria, the spear punches a hole into them, leaving them to die and release their genetic material, which the predator pulls into itself. This spear-killing, predatory behavior is triggered by the bacterium's environment. The cholera bacterium naturally lives in water, such as the sea, where it attaches onto small planktonic crustaceans. There, it feeds on the main component of their shells: a sugar polymer called chitin. When chitin is available, V. cholerae goes into an aggressive survival mode called "natural competence." When in this mode, V. cholerae attacks neighboring bacteria with its spear - even if they are of the same species. Dr. Blokesch set out to explore how V. cholerae uses this behavior to compete for survival in nature.
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