Niche dimensions of marine biotic powerhouse

Marine bacteria serve as regulators within and between ocean systems, processing about a quarter of all the photosynthesis on Earth. Because of their microscopic size and very short life span of a single day, learning what controls their activities, what nutrients they are trying to find, what molecules they grow on, and whether they interact with other microbes has been nearly impossible. In classical ecological terms, researchers don't have ways to determine the dimensions of their niches.  But a new study from UGA marine scientists published recently in the journal Nature Microbiology describes the use an 'invasion study', in which a bacterium in a consistent physiological state is added into different natural seawater communities.

In the ocean, bacteria mediate flux between major carbon reservoirs, control nutrient availability and participate in marine food webs. Many environmental factors govern these activities, including seawater mixing, photosynthetically active irradiance levels^1,2, organic resources³, nutrients^3,4, and mutualistic and antagonistic interactions with other species^5,6. These factors form the dimensions of each bacterial species’ niche, a foundational ecological concept in which the abiotic and biotic variables that influence the birth and death rates of a species determine where it can exist in nature^7,8.

Identifying the dimensions of marine bacterial niches promises to improve understanding and predictability of the processes that drive ocean biogeochemistry.

The novel 'invasive study' idea allowed the team to observe the factors in the bacterium's environment affecting its ability to survive by identifying the genes it turns up or down.

"We now know what metals it needs, what substrates it uses, and how these change with different primary producers," said Mary Ann Moran, Regents Professor and Distinguished Research Professor in the department of marine sciences and co-author on the paper with Postdoctoral Research Associate Brent Nowinski.

"The bacterial processing of recently fixed carbon is one of the largest, and fastest, fluxes of organic carbon in the biosphere. This paper helps us understand the factors that bacteria are most vulnerable to as the ocean's conditions and organisms shift," Moran said.

Image: Sun rise over the Georgia Bight, November 2019. Photo by author.