Oxygen is essential for most life on Earth, and sunlight is needed to produce it. Researchers caught a common ocean-dwelling microbe breaking all the rules.
Scientists have found that a group of organisms called oxidizing ammonia archaea are able to survive in dark environments by producing oxygen on their own. They use a biological process that has never been seen before.
While it's been established that these microbes can live in environments where oxygen is scarce, what hasn't been clear is what they get up to there and how long they're staying alive. That is the inspiration behind the new research.
"These guys are abundant in the oceans and they play an important role in the nitrogen cycle," says Beate Kraft, a microbiologist from the University of Southern Danes.
It has been a long-standing puzzle why they are abundant in waters with no oxygen. We wondered if they just hang out there with no function. Are they ghost cells?
Every fifth cell in a bucket of ocean water will be an organisms, that's how common they are. The researchers took the microbes from their natural habitat and put them in the lab.
The team wanted to know what would happen when there was no sunlight to produce new oxygen. When N. Maritimus moves from oxygen-rich to oxygen-depleted waters, the same thing happens.
They found that the organisms produced their own oxygen and nitrogen gas to make nitrite.
"We saw how they used up all the oxygen in the water, and then to our surprise, within minutes, oxygen levels started increasing again," says Don Canfield, from the University of Southern Danes. That was very exciting.
The amount of oxygen produced appears to be relatively small, but it does look to be different to the few oxygen-without-Sunlight processes that we already have.
The new pathway shows that the oxygen production from N. maritimus is related to the production of gaseous nitrogen. In an oxygen-depleted environment, the microbes are converting ammonia into nitrite, a process they use to metabolize energy.
The team detected traces of nitrogen gas and oxygen in the air.
This process removes nitrogen from the environment, which is a new twist in the nitrogen cycle. This finding could have far-reaching consequences.
If this lifestyle is common in the oceans, it will force us to rethink our understanding of the marine nitrogen cycle.
"My next step is to investigate the phenomenon we saw in our lab cultures in the ocean spots around the world."
The research has been published.