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Scientists find how cholera bacterium use a hooked appendix for various purposes

Vibrio cholerae is the bacterium that causes cholera: it infects the small intestine and causes diarrhoea and dehydration. This bacterium often lives on the shells of crustaceans, exoskeletons composed of a sugar polymer, called chitin, which the bacterium feeds on.

To hold on to the shells, but also to perform other tasks, these bacteria use an appendix as if it were a sort of grappling hook thanks to which the Vibrio cholerae, and several other species of bacteria, detect the surfaces and stick to them for feeding.

With regard to this particular characteristic of these bacteria, a group of researchers carried out research published in Nature Microbiology, a study that obtained important new information on how bacteria colonize surfaces and how they distinguish the individuals around them, considered fundamental biological issues.

With these “grappling hooks,” called type IV hairs, they can also take DNA from neighboring bacteria and perform other basic tasks for their survival including the recognition of other members of their own species. “The idea is that bacteria can throw these long ropes, hook onto something and rewind it to themselves,” reports David Adams, one of the researchers. How they work exactly and what else they are able to do, in addition to being able to stick to DNA, is still partly unknown.

Now, however, researchers have managed to directly observe the pili in live cholera bacteria using a technique called cysteine labeling. According to one of the researchers involved in the study, Melanie Blokesch, this is an “important milestone: even though we had established some time ago that these structures were there, seeing them moving in real time was something very special.”

They discovered that different strains of V. cholerae produce slightly different variants of the pili and that they naturally form a dense network of self-interacting pili that bind closely to the surface of the chitin and are necessary for the bacterium to remain attached during the flow of water.