Finding microorganisms that receive energy from nitrate respiration from symbiotes such as mitochondria

by Max Planck Institute for Marine Microbiology, S. Ahmerkamp

Until now, it was thought that only mitochondria supply energy to eukaryotic cells, but research by the Max Planck Institute for Marine Microbiology and others has shown that symbiotic bacteria different from mitochondria can also supply energy. It was found from the discovery of ciliates that obtain energy from symbiotic organisms that perform

New form of symbiosis discovered
https://www.mpi-bremen.de/en/New-form-of-symbiosis-discovered.html

Strange microbe “breathes” nitrates using a mitochondria-like symbiont | Ars Technica
https://arstechnica.com/science/2021/03/nitrate-breathing-microorganism-offers-glimpse-into-evolutions-past/

In 2016, biologist Jana Milucka and colleagues at the Max Planck Genome Center took samples from a depth of about 190 meters on Lake Zug, Switzerland. Lake Zug was chosen because it had a stratified structure with an oxygen-containing layer at the top and an oxygen-free layer near the bottom, so the organisms that live at the bottom are oxygen. It was because it was thought that it was evolving so that it could live without it.


Milucka et al., Who examined the nucleotide sequences of the DNA of all living organisms obtained from the collected samples, discovered the genome of a bacterium that has a complete metabolic pathway for nitrate respiration. This genome was similar to that of symbiotic microorganisms that live in the body of insects. However, I did not think that insects lived at the bottom of the lake, and at this point the genome could not be explained.

For this reason, Milucka and his colleagues, who began looking for symbiotic candidates, collected samples again at Lake Zug in February 2020, just before the lockdown and border closure due to the new coronavirus infection.

He discovered that a bacterium named 'Candidatus Azoamicus ciliaticola' coexists with a ciliate species called Plagiopylea by supplying energy through nitrate respiration. The symbiosis of Plagiopylea and Candidatus Azoamicus ciliaticola is believed to date from 200 to 300 million years ago.

Such 'symbiosis between eukaryotes and bacteria' itself is not uncommon, but it is rare that bacteria evolved together with the host eukaryotic organisms, and as a result, they had no choice but to coexist. It seems that it is rare to supply the host with adenosine triphosphate (ATP), which is called the energy currency of the living body.

This discovery suggests that eukaryotes with mitochondrial derivatives may acquire internal symbiotic agents that supply energy secondarily and complement or replace mitochondrial function. ..