Scientists reveal the structure of bacteria's 'propellers' in near atomic detail

Image:  By Carsten Steger - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=126058647

 

Bacteria push themselves forward by coiling long, threadlike appendages into corkscrew shapes that act as makeshift propellers. But how exactly they do this has baffled scientists, because the "propellers" are made of a single protein.

 

Researchers used cryo-EM and advanced computer modelling to reveal what no traditional light microscope could see: the strange structure of these propellers at the level of individual atoms.

 

Blueprints for Bacteria's 'Supercoils'

 

Different bacteria have one or many appendages known as a flagellum, or, in the plural, flagella. A flagellum is made of thousands of subunits, but all these subunits are exactly the same. You might think that such a tail would be straight, or at best a bit flexible, but that would leave the bacteria unable to move. That's because such shapes can't generate thrust. It takes a rotating, corkscrew-like propeller to push a bacterium forward.

 

Scientists call the formation of this shape "supercoiling," and now, after more than 50 years, they understand how bacteria do it.

 

Using cryo-EM, the researchers found that the protein that makes up the flagellum can exist in 11 different states. It is the precise mixture of these states that causes the corkscrew shape to form.

 

 

It has been known that the propeller in bacteria is quite different than similar propellers used by hearty one-celled organisms called archaea. Archaea are found in some of the most extreme environments on Earth, such as in nearly boiling pools of acid, the very bottom of the ocean and in petroleum deposits deep in the ground.

 

The scientists used cryo-EM to examine the flagella of one form of archaea, Saccharolobus islandicus, and found that the protein forming its flagellum exists in 10 different states.

 

S. solfataricus is a species of thermophilic archaeon. The organism known to grow chemoorganotrophically, in presence of oxygen, on a variety of organic compounds such as sugars, alcohols, amino acids and aromatic compounds like phenol

While the details were quite different than what the researchers saw in bacteria, the result was the same, with the filaments forming regular corkscrews. They conclude that this is an example of "convergent evolution" -- when nature arrives at similar solutions via very different means. This shows that even though bacteria and archaea's propellers are similar in form and function, the organisms evolved those traits independently.


The researchers have published their findings in the scientific journal Cell, titled “Convergent evolution in the supercoiling of prokaryotic flagellar filaments.”

 Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (http://www.pharmamicroresources.com/)

Archaea can produce vitamin B12

University of Washington researchers used new tools to measure and track B-12 vitamins in the ocean. From this, oceanographers have found that archaea, in this case species that are marine microorganism, can produce B-12 vitamins in the open ocean. This is a vitamin that is generally elusive in the ocean environment.

For their study, the researchers used high-tech tools, including liquid chromatography and mass spectrometry, to identify the tiny amount of vitamins among all the dissolved matter and salt in the seawater.

With the findings, the research team hopes to learn which microbes are producing B-12 vitamins where, to better understand how the base of the marine food web works, how it might alter in a changing environment, how oceans might help regulate atmospheric carbon dioxide, and where marine animals could go to get a well-balanced diet.

Posted by Victor Grayson