Natures wonders: bacteria have grappling hooks (Introduction)

by David Turell @, Monday, June 10, 2019, 17:08 (16 days ago) @ David Turell

Holds them on hard surfaces in oceans:

"The cholera bacterium Vibrio cholerae infects the small intestine, causing diarrhea and severe dehydration. It lives in salty water, such as seas, oceans and estuaries, attaching itself to the shells of crustaceans. These exoskeletons are composed of a sugary polymer called chitin, and provide a rich source of food for the cholera bacterium—allowing it to grow and survive in the environment.

"To do all this, V. cholerae uses an appendage that's "a bit like a grappling hook,"' says lead researcher David Adams. "The idea is that bacteria can throw out these long ropes, hook onto something, and reel it back in."

"These lines are actually the product of highly versatile nano-machines known as type IV pili, which are used by many bacterial species for motility, sensing surfaces and sticking to them, and even taking up DNA from neighboring bacteria. Consequently, type IV pili are considered critical for the environmental survival and pathogenesis of not just V. cholerae, but a wide range of bacteria.


"The biggest insight came, however, when researchers disrupted the motor that powers pilus retraction, revealing that these ropes could also self-interact with each other, and in doing so, allow cells to stick together. Curiously, different strains of V. cholerae produce slightly different variants of the PilA subunit, which forms the major building block of the pilus. Remarkably, this creates a set of highly specific interactions that can be used as an identifier between strains ensuring that like only pairs with like.

"Finally, when researchers visualized V. cholerae growing under more realistic conditions upon chitin surfaces, they revealed that these DNA-uptake pili naturally form dense networks of self-interacting pili. These pili bind tightly to the chitin surface and are required for the bacterium to stay attached during water flow. Thus, the DNA-uptake pilus is a multifunctional toolkit for chitin surface colonization and kin recognition and the results of this work will help to advance our understanding of how the cholera bacterium survives in the natural environment."

Comment: These external pili are like the spears bacteria use against amoeba. These complex mechanisms are very difficult to imagine as occurring by chance. How did V. cholera survive in oceans before their development since their use is in attaching to a needed food supply? Design is necessary.

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