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American scientists have examined at the atomic level the structure of flagella that help E. coli and other bacteria move, according to the University of Virginia.

The bacteria move forward by twisting long filamentous appendages – flagella – into a corkscrew shape so that they act like propellers. But exactly how they do it was unclear, because the "propellers" are made of a single protein.

In this work, the researchers used cryo-electron microscopy and advanced computer modeling techniques to reveal what no traditional microscope could see. They found that the protein that makes up the flagellum can exist in 11 different states. It is the exact mixture of these states that leads to the formation of the corkscrew shape.

The "propeller" of bacteria is very different from similar "propellers" used by archaea. Archaea – unicellular organisms – are found in the most extreme conditions on Earth, for example, in almost boiling pools with acid, at the very bottom of the ocean and in oil fields deep underground.

With the help of cryo-EM, scientists examined, among other things, the flagella of one of the archaea forms, Saccharolobus islandicus, and found that the protein forming their flagella exists in 10 different states. Although the details were very different from what the researchers saw in the bacteria, the result was the same: the filaments were spiked. Scientists conclude that this is an example of "convergent evolution" — when nature comes to the same decisions in completely different ways. This shows that although the "propellers" of bacteria and archaea are similar in shape and function, organisms have developed these traits independently of each other.

"Although for 50 years there have been models of how these filaments can form such regular spiral shapes, now we have determined the structure of these filaments at the atomic level,— said Edward H. Egelman (Edward H. Egelman) from the Department of Biochemistry and Molecular Genetics at the University of Washington. "We can show that these models were wrong, and our discovery will help pave the way for technologies that can be based on such miniature propellers."

The article was published in the journal Cell
The information is taken from the portal "Scientific Russia" (https://scientificrussia.ru/)

PHOTO © Mark A.B. Kreutzberger et al./ Cell, 2022

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