Bacteria that Causes Cholera Uses Tiny Spear to Harpoon New DNA

Cholera is caused by the bacterium, Vibrio cholera, and can impact the small intestine. Now, scientists are learning more about this bacterium; it turns out that it has a tiny spear to stab and kill neighboring bacteria, stealing their DNA.

The researchers discovered this spear-killing, predatory behavior in V. cholera when they looked at how it competed with surrounding bacteria. The molecular killing device acts a bit like a spring-loaded spear that is constantly shooting out. The "weapon" itself is called the "type IV secretion system" (T6SS), and is seen in many different types of bacteria. In the case of V. cholera, when the bacterium comes close to other bacteria, the spear punches a hole into them and causes them to die and release their genetic material. V. cholera then pulls that DNA into itself.

The researchers actually grew V. cholera on chitin surfaces that simulated their natural habitat on crustaceans. What they found was that the tiny spear actually wasn't just part of the bacteria's natural survival system, but also contributed to gene transfer. This gene transfer can make the bacterium more resistant to threats, such as antibiotics.

"Using this mode of DNA acquisition, a single V. cholera cell can absorb fragments containing more than 40 genes from another bacterium," said Melanie Blokesch, one of the researchers, in a news release. "That's an enormous amount of new genetic information."

The method itself is known as horizontal gene transfer, which is a widespread phenomenon in bacteria. It contributes to the dispersal of virulence factors and antibiotic resistance. By better understanding how bacteria manage this feat, the researchers could potentially better understand the evolutionary forces that drive the formation of human pathogens.

The findings are published in the journal Science.

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