Breathing poison: Microbial Life on Nitric Oxide Respiration
Published:25 Jul.2023 Source:Max Planck Institute for Marine Microbiology
Nitric oxide (NO) is a fascinating and versatile molecule, important for all living things as well as the environment. It is highly reactive and toxic, organisms use it as a signaling molecule, it depletes the ozone layer in our planet's atmosphere, and it is the precursor of the greenhouse gas nitrous oxide (N2O). Moreover, NO might have played a fundamental role in the emergence and evolution of life on Earth, as it was available as a high-energy oxidant long before there was oxygen.
Thus, despite its toxicity, it makes perfect sense that microbes use NO to grow. However, research on the topic is scarce and, to date, microbes growing on it have not been cultivated. That has now changed, as reported by scientists around Paloma Garrido Amador and Boran Kartal from the Max Planck Institute for Marine Microbiology in Bremen, Germany, in the journal Nature Microbiology. They have managed to enrich two yet unknown species of microorganisms growing on NO in bioreactors and reveal exciting aspects of their lifestyle.
The study started off with a trip to Bremen's wastewater treatment plant. "We collected sludge from their denitrifying tank," Garrido Amador tells. "Back in our lab, we added the sludge to one of our bioreactors and we started the incubation by feeding it with NO." Bioreactors are designed and optimized to grow microorganisms under controlled conditions, which closely mimic their natural environment. This bioreactor setup was very challenging, though, Garrido Amador reports, "Because NO is toxic, we needed special equipment and had to take great care when handling them for our own safety. Nevertheless, we managed to keep the cultures growing for more than four years now -- and they are still happy and healthy!"