The 3 in 1 Toolbox of the Cholera Bacteria for Life in the Ocean

[ad_1]

Bacteria are the most abundant form of life on Earth. The ocean is very abundant with small particles and debris, some inert, others very nutritious. But researchers want to know how bacteria differentiate these surfaces, how they hang in moving water, and how they recognize each other so they can work together.

The cholera bacterium Vibrio cholerae infects the small intestine, causing diarrhea and severe dehydration. It lives in salt water such as seas, oceans and estuaries and attaches to shellfish shells. These exoskeletons are composed of a sweet polymer called chitin and are a rich food source for the cholera bacterium, allowing it to grow and survive in the environment.

To do all that, V. cholerae uses an appendix that "looks a bit like a grappling hook," says principal investigator David Adams. "The idea is that bacteria can throw those long ropes, hang on to something and put it back in place."

These lines are in fact the product of very versatile nano-machines known as type IV pili, which are used by many bacterial species for motility, surface detection and adhesion, and even the collection of bacteria. DNA of neighboring bacteria. As a result, type IV pili are considered critical for the survival and pathogenesis of V. choleraebut a wide range of bacteria.

In the last decade or so, Melanie Blokesch's group has established that V. cholerae produces these pili of DNA uptake only on chitinous surfaces and shows that they are essential for DNA uptake. But their functioning and what they might have been else remained somewhat elusive, which is why the purpose of this study published in Microbiology of nature.

Directly observe the DNA absorption pili live V. cholerae bacteria, the researchers used a technique called cysteine ​​labeling. They were able to establish that, as expected, pili are very dynamic, extending and retracting to take DNA.

"It was a milestone," said Melanie Blokesch, laboratory manager. "Even though we had established some time ago that these structures existed, seeing them evolve in real time was something quite special.

However, the biggest idea came when the researchers disrupted the motor of retraction of the pilus, revealing that these strings could also interact with each other, thus allowing the cells to remain stuck to each other. Curiously, different strains of V. cholerae produce slightly different variants of the PilA subunit, which is the main building block of the pilus. Remarkably, this creates a set of very specific interactions that can be used as an identifier between strains, thus ensuring that only pairs with similar ones.

Finally, when the researchers visualized V. cholerae growing under more realistic conditions on chitin surfaces, they revealed that these DNA-absorbing pili naturally form a dense network of self-interacting pili. These pili bind closely to the surface of the chitin and are necessary for the bacteria to remain attached during the flow of water. Thus, the DNA uptake pilus is a multifunctional toolbox for colonization of the chitin surface and the recognition of kines, and the results of this work will help us better understand how the cholera bacterium survives in the body. 'natural environment. This knowledge, on the other hand, is important to better understand the transmission to humans in endemic areas of cholera.