MAR 18, 2019 10:25 AM PDT

Some Microbes Can Live on Nitric Oxide

WRITTEN BY: Carmen Leitch

Nitric oxide (NO), a colorless gas, plays an important role in a wide array of different processes. It’s a free radical, which means it has a highly reactive unpaired electron. While NO has important physiological roles, it is also very toxic. It's produced by combustion engines in vehicles, it can erode the ozone layer that's protecting our planet from UV rays, and is a precursor to nitrous oxide, a greenhouse gas. Because of its long history on the planet as a high-energy molecule, it’s been thought to play a role in the emergence and evolution of life. New research has lent credence to that hypothesis.

Kuenenia stuttgartiensis, here seen under a transmission electron microscope, is a model anammox microorganism, which grows as single cells. It is a freshwater species also found in wastewater treatment plants. / Credit: Laura van Niftrik

Reporting in Nature Communications, Max-Planck-scientist Boran Kartal and colleagues have shown how microbes can make use of nitric oxide. Until now, researchers haven’t known whether nitric oxide can help support life. Kartal’s team at Radboud University in the Netherlands has found that anaerobic bacteria that oxidize ammonia (also known as anammox) can directly utilize nitric oxide to grow. They do so by coupling reactions - nitric oxide reduction with ammonium oxidation, making only dinitrogen gas (N2) in the process.

"These findings change our understanding of the earth's nitrogen cycle. Nitric oxide has been primarily thought of as a toxin, but now we show that anammox bacteria can make a living from converting NO to N2", says Kartal. 

There are microbes known to change NO to nitrous oxide (N2O). N2 is harmless, but N2O is a powerful greenhouse gas. Every molecule that is converted to N2 instead of N2O is making a contribution to climate change.

“In this way, anammox bacteria reduce the amount of NO available for N2O production, and reduce the amount of released greenhouse gas,” explained Kartal. “Our work is interesting in understanding how anammox bacteria can regulate N2O and NO emissions from natural and man-made ecosystems, such as wastewater treatment plants, where these microorganisms contribute significantly to N2-release to the atmosphere.”

An anammox culture is in a membrane bioreactor. The red color is due to the heme c group of the protein cytochrome c that plays an important role in the anammox metabolism. / Credit: B. Kartal

This study could change or throw new variables into climate change modeling. 

“Anammox, a globally important microbial process of the nitrogen cycle relevant for the earth's climate, does not work the way we assumed it did.” There are anammox bacteria all over the planet, and many of them could be using nitric oxide directly too, the scientists noted. “In this sense, the anammox microbes growing on nitric oxide could also be basically everywhere,” added Kartal.

The researchers want to know more about how microbes that use nitric oxide are impacting different ecosystems. They are curious about how nitric oxide is used in environments that have oxygen, and those without it. “Basically, we want to understand how organisms can make a living on NO,” concluded Kartal.

You can learn more about how nitrogen is involved in climate change from the video featuring David Reay of the University of Edinburgh.

Sources: AAAS/Eurkealert! via Max Planck Institute for Marine Biotechnology, Nature Communications

About the Author
  • Experienced research scientist and technical expert with authorships on over 30 peer-reviewed publications, traveler to over 70 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
AUG 18, 2020
Microbiology
The Science of Pesto
AUG 18, 2020
The Science of Pesto
  The word pesto comes from the Genovese word pestâ (pestare in Italian) which means “to pound” o ...
SEP 04, 2020
Microbiology
Researchers Discover a Way to Use Microbes to Help Make Plastic
SEP 04, 2020
Researchers Discover a Way to Use Microbes to Help Make Plastic
Researchers have discovered that some bacteria can make ethylene in a way we never knew about; microbes that metabolize ...
OCT 26, 2020
Microbiology
A Network of Fungi Helps Trees Grow
OCT 26, 2020
A Network of Fungi Helps Trees Grow
Trees rely on a network of fungal friends for good health. Communities of trees can share nutrients and other essentail ...
NOV 08, 2020
Microbiology
Seasonal Illness - Is the Sun Involved?
NOV 08, 2020
Seasonal Illness - Is the Sun Involved?
There is a cold and flu season, and many researchers have tried to explain why the viruses that cause these illnesses te ...
NOV 09, 2020
Microbiology
Fighting COVID-19 with Help From Llamas
NOV 09, 2020
Fighting COVID-19 with Help From Llamas
Camelids, which include llamas, alpacas and camels have immune systems that generate two kinds of antibodies when confro ...
NOV 19, 2020
Immunology
Parasitic Worms Help Unravel the Immune Mechanisms Underlying Chronic Disease
NOV 19, 2020
Parasitic Worms Help Unravel the Immune Mechanisms Underlying Chronic Disease
Parasitic worms known as helminths have a complicated relationship with the immune systems of the hosts they invade. Ter ...
Loading Comments...