Microbes produce oxygen in the dark

Date:
January 6, 2022
Source:
University of Southern Denmark
Summary:
It is common knowledge that there would be no oxygen on Earth
were it not for sunlight; the key component in photosynthesis. Now
researchers have made the surprising discovery that oxygen is also
produced without sunlight, possibly deep below the ocean surface.



FULL STORY ==========================================================================
It is common knowledge that there would be no oxygen on Earth were it
not for sunlight; the key component in photosynthesis. Now researchers
have made the surprising discovery that oxygen is also produced without sunlight, possibly deep below the ocean surface. There is more going on
in the deep, dark ocean waters than you may think: Uncountable numbers of invisible microorganisms go about their daily lives in the water columns,
and now researchers have discovered that some of them produce oxygen in
an unexpected way.


==========================================================================
The study is led by Beate Kraft and Donald E. Canfield from University
of Southern Denmark and published in the journal Science. Contributing
authors are Nico Jehmlich, Morten Larsen, Laura Bristow, Martin Ko"nneke
and Bo Thamdrup.

Beate Kraft is an assistant professor at Department of Biology. Her
focus is on microbial physiology and biochemistry, and her research
is supported by a Villum Young Investigator Grant. Don E. Canfield is
Professor of Ecology at the Department of Biology and Danish Institute
for Andvance Study chair of Biology.

Oxygen is vital for life on Earth, and is mainly produced by plants,
algae and cyanobacteria via photosynthesis. A few microbes are known to
make oxygen without sunlight, but so far they have only been discovered
in very limited quantities and in very specific habitats.

Enter the ocean living microbe Nitrosopumilus maritimusand its cousins,
called ammonia oxidizing archaea.

Ghost organisms hanging out in the dark "These guys are really abundant in
the oceans, where they play an important role in the nitrogen cycle. For
this they need oxygen, so it has been a long standing puzzle why they are
also very abundant in waters where there is no oxygen," says biologist
Beate Kraft, adding: -"We thought; They just hang out there with no
function; they must be some kind of ghost cells."


==========================================================================
But there was something puzzling to this; "These microbes are socommon,
that every 5th cell in a bucket of sea water is one of them," adds Don Canfield, co-author of the paper.

So the researchers became curious; could they have a function in the
oxygen depleted water after all? They make their own oxygen Beate Kraft decided to test them in the lab; "We wanted to see what would happen if
they ran out of oxygen -- like they do when they move from the oxygen
rich waters to oxygen depleted waters. Would they survive?"


==========================================================================
"We saw how they used up all the oxygen in the water, and then to our
surprise, within minutes, oxygen levels started increasing again. That
was very exciting!," Don Canfield recalls.

Enough for me and my friends Nitrosopumilus maritimusturned out to be
able to make oxygen in a dark environment. Not much -- not at all so
much that it would influence oxygen levels on Earth, but enough to keep
itself going.

"If they produce a little more oxygen than they need themselves, it will quickly be taken by other organisms in their neighborhood, so this oxygen
would never leave the ocean," Beate Kraft explains.

But what effect do they have on the environment they live in, these
extremely abundant oxygen-producing microbes? New ocean expedition
Researchers already knew that the ammonia oxidizing archaea are
microorganisms, that keep the global nitrogen cycle going, but they were
not aware of the full extent of their capabilities.

In the newly discovered pathway, Nitrosopumilus maritimus couples the
oxygen production to the production of gasous nitrogen. By doing so they
remove bioavailable nitrogen from the environment.

"If this lifestyle is widespread in the oceans, it certainly forces
us to rethink our current understanding of the marine nitrogen cycle,"
adds Beate Kraft.

"My next step is to investigate the phenomenon we saw in our lab cultures
in oxygen depleted waters in various ocean spots around the world,"
she adds.

Her research team has already taken samples in Mariager Fjord in Denmark,
and next stop is the waters off Mexico and Costa Rica.

========================================================================== Story Source: Materials provided by
University_of_Southern_Denmark. Original written by Birgitte
Svennevig. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Beate Kraft, Nico Jehmlich, Morten Larsen, Laura A. Bristow, Martin
Ko"nneke, Bo Thamdrup, Donald E. Canfield. Oxygen and nitrogen
production by an ammonia-oxidizing archaeon. Science, 2022; 375
(6576): 97 DOI: 10.1126/science.abe6733 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220106143640.htm

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