Friday, 15 May 2020

New metabolism discovered in bacteria


Microbiologists have discovered how the bacterium Acetobacterium woodii uses hydrogen in a kind of cycle to conserve energy. The bacterium lives in an environment without oxygen, and thanks to hydrogen cycling, it can exist independent of other species of bacteria.

They make sauerkraut sour, turn milk into yogurt and cheese, and give rye bread its intensive flavour: bacteria that ferment nutrients instead of using oxygen to extract their energy.

Acetobacterium woodii (short: A. woodii) is one of these anaerobic living microbes. Cheese and bread are not its line of business -- it lives far from oxygen in the sediments on the floor of the ocean, and can also be found in sewage treatment plants and the intestines of termites.

These biotopes are teeming with microbes that use the organic substances to their advantage in different ways. A number of bacteria ferment sugars, fatty acids and alcohols to acetic acid, also creating hydrogen (H2) in the process. In higher concentration, however, hydrogen inhibits the fermentation -- too much hydrogen stops the fermentation reaction. For this reason, fermenting bacteria live together with microbes that depend on precisely this hydrogen, methanogens, for example, that create methane from hydrogen and carbon dioxide and thus gain energy. Both partners profit from this association -- and are simultaneously so dependent on each other that neither one can survive without the other.


A. woodii masters both disciplines of the anaerobic "hydrogen association": it can ferment organic substances into acetic acid, and can also form acetic acid from carbon dioxide and hydrogen. In doing so, A. woodii recycles the important hydrogen within its own cell, as has now been discovered by the microbiologists in Professor Volker Müller's team at the Institute for Molecular Biosciences at Goethe University Frankfurt.

See:

Anja Wiechmann, Sarah Ciurus, Florian Oswald, Vinca N. Seiler, Volker Müller. It does not always take two to tango: “Syntrophy” via hydrogen cycling in one bacterial cell. The ISME Journal, 2020; DOI: 10.1038/s41396-020-0627-1

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

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