Shift work helps marine microbes share scarce ocean resources

Angela Boysen (left) and colleagues in July 2015 lowered an instrument at the study site in the subtropical North Pacific Gyre, north of Hawaii. This instrument collected water samples at different depths that the researchers analyzed. Credit: Dror Sheetret/Simmons Collaboration on Ocean Operations and the Environment

Although they may be small, microorganisms are the most abundant life form in the ocean. Marine microbes are responsible for the production of nearly half of life’s usable organic carbon. Many marine microbes live near the surface, depending on energy from the sun for photosynthesis.

However, between a poor supply and intense competition for some key nutrients, such as nitrogen, in the open ocean, scientists have puzzled over the sheer diversity of microbial species found there. Researchers from the University of Washington, in collaboration with researchers from 12 other institutions, have shown that time of day is key, according to a study published Jan. Nature’s environment and evolution.

The effort began in 2015, when scientists at Simons Collaboration on Ocean Processes and Ecology, a program now co-led by University of Washington professor of oceanography Ginger Armprost, looked at microbes at the surface of the subtropical North Pacific, the largest contiguous extension for the earth. Ocean.

“[We were interested in] Understand how this fluctuation in photosynthesis spreads during the day and its absence at night through the microbial community [in the ocean], explained co-first author Angela Boysen, who did the work as a doctoral student at the University of Wisconsin and is now a postdoctoral researcher at the University of Chicago. It affects how the overall ecosystem functions, how much carbon is stored, where the carbon moves, and how organisms can interact with each other.”

By incorporating data about the timing of metabolic processes of different microbes at the ocean’s surface during the 24-hour light cycle — from gene transcription for proteins used in metabolism to the synthesis of molecules, such as lipids, in the microbes’ cells — the researchers discovered that the symbiosis of such diverse microbes may Not dictated by competition, but by the timing of their nitrogen uptake.

With successive uptake of the primary nitrogen element, “instead of having to compete with the entire field, [microbes] Only to compete with the organisms that share this specific transformation [them]. Perhaps this is one way in which competition is tempered a little bit and could facilitate the ability of all these diverse microbes to live from the same nutrient source,” said co-first author Daniel Morator, a doctoral student at Georgia Institute of Technology.

Because of the multidisciplinary team on the 2015 research journey, data on nearly their entire metabolism were collected simultaneously from the same water every four hours, giving researchers an unprecedented look at how metabolic activity varies between these microbes throughout the 24-hour cycle.

Matthew Hark, co-first author and research scientist at the Gloucester Marine Genomics Institute.

The data revealed that most activity occurred at four time points: dusk (6 pm), night (2 am), morning (6 am) and afternoon (between 10 am and 2 pm). While these times were important for many types of microbes, the activities of the different groups each time were not uniform.

“Recognizing that different types of microbes gain nitrogen at different times of the day helps answer a longstanding question in oceanography: How can there be such an amazing diversity of life, all essentially in the same place and at the same time?” said co-author Anitra Ingalls, a professor of oceanography at the University of Washington. “Being able to explain the reasons behind this diversity will help oceanographers better predict how these communities will shift as the ocean changes.”

Sacha Kozel, a University of Washington research scientist in oceanography, is also a co-author.

Microbes produce oxygen in the dark

more information:
Daniel Morator et al., Complex marine microbial communities segment the metabolism of scarce resources over the diel cycle, Nature’s environment and evolution (2022). DOI: 10.1038 / s41559-021-01606-w

Presented by the University of Washington

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