SEP 15, 2020 5:31 AM PDT

If They Must, Methane-Eating Microbes Will Consume Ammonia

WRITTEN BY: Carmen Leitch

There are many different kinds of microbes, and some can use unusual substances to survive. Methanotrophs, for example, oxidize methane (CH4) to carbon dioxide (CO2). For methanotrophs, ammonia (NH3) is structurally similar enough to methane for them to be able to metabolize it, producing nitrite (NO2) in the process. Researchers have now learned more about how that happens. Their findings were reported in the Proceedings of the National Academy of Sciences.

Nitric oxide (NO) can play a variety of roles in our environment and in biology. It acts as a signaling molecule in biochemistry, but it also responsible for depleting the ozone layer, and is an intermediate in the global nitrogen cycle. Methanotrophs that are exposed to ammonia, which happens often because of the abundance of fertilizers in the world, also rely on nitric oxide.

Methanotrophs co-metabolize ammonia, first generating hydroxylamine (H3NO), which interferes with cellular processes and can cause cell death. It's critical for microbes to eliminate the hydroxylamine before damage happens.

 "Carrying a hydroxylamine-converting enzyme is a matter of life or death for methane-eating microbes," explained Boran Kartal, head of the Microbial Physiology Group at the Max Planck Institute for Marine Microbiology in Bremen, Germany.

Image credit: Pikist

In this work, Kartal and colleagues focused on a methanotroph that originated in the hot, acidic, volcanic mud pots of Vesuvius, Italy, and is known as Methylacidiphilum fumariolicum.

"From this microbe, we purified a hydroxylamine oxidoreductase (mHAO) enzyme. Previously it was believed that mHAO enzyme would oxidize hydroxylamine to nitrite in methanotrophs. We now showed that it actually rapidly produces NO," said Kartal. "It is now clear that enzymatically there is not much difference between aerobic ammonia- and methane-oxidizing bacteria. Using essentially the same set of enzymes, methanotrophs can act as de facto ammonia oxidizers in the environment. Still, how these microbes oxidize NO further to nitrite remains unknown."

The mHAO enzyme has also adapted to the hot mud, suggested Karatl.

"At the amino acid level, the mHAO and its counterpart from ammonia oxidizers are very similar, but the protein we isolated from M. fumariolicum thrives at temperatures up to 80°C, almost 30°C above the temperature optimum of their "actual" ammonia-oxidizing relatives. Understanding how so similar enzymes have such different temperature optima and range will be very interesting to investigate," he added.

"Currently there are no known methanotrophs that can make a living out of ammonia oxidation to nitrite via NO, but there could be methanotrophs out there that found a way to connect ammonia conversion to cell growth."

Sources: AAAS/Eurekalert! via Max Planck Institute, Proceedings of the National Academy of Sciences

 

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
DEC 15, 2020
Immunology
Yes, You Should Get Your Flu Vaccine.
DEC 15, 2020
Yes, You Should Get Your Flu Vaccine.
A recent study published in Science Translational Medicine has provided fresh insights on how our immune systems protect ...
JAN 20, 2021
Immunology
Gut Bacteria's Poison Arrows Exposed
JAN 20, 2021
Gut Bacteria's Poison Arrows Exposed
Bacteria armed with toxin bombs and excruciating abdominal pains caused by raging inflammation in the gut. While the cau ...
JAN 23, 2021
Microbiology
Host Vouchering & How Can It Improve Pandemic Response
JAN 23, 2021
Host Vouchering & How Can It Improve Pandemic Response
About a year ago, I wrote about the virus that would come to be known as SARS-CoV-2 for the first time. And while we've ...
JAN 24, 2021
Microbiology
Cholesterol Enables SARS-CoV-2 to Invade & Create 'Mega-Cells'
JAN 24, 2021
Cholesterol Enables SARS-CoV-2 to Invade & Create 'Mega-Cells'
To cause the COVID-19 illness, the SARS-CoV-2 virus first has to get into cells. To do so, it uses something called a sp ...
FEB 19, 2021
Microbiology
Weed Killers May Raise Levels of Antibiotic-Resistant Microbes in Soil
FEB 19, 2021
Weed Killers May Raise Levels of Antibiotic-Resistant Microbes in Soil
Chemicals that are designed to kill weeds, known as herbicides, can apparently raise the levels of antibiotic resistant ...
FEB 25, 2021
Coronavirus
COVID Long-Haulers Get Official Recognition
FEB 25, 2021
COVID Long-Haulers Get Official Recognition
For months, many people that have recovered from cases of COVID-19 have reported experiencing a range of lingering healt ...
Loading Comments...