Cooperating in the deep

Microbial species form symbiotic communities that cooperate to exploit resources in complex ecosystems, according to a new study.

The team, which was led by Sarah Preheim and Scott Olesen at MIT and included Jorge Rodriguez of the UAE’s Masdar Institute of Science and Technology, investigated the structure of microbial communities across a gradient of water temperatures and chemicals in a lake¹. 

The researchers sequenced DNA from microorganisms found in water samples collected at different depths, as well as measuring various geochemical parameters. Their analysis showed that different groups of microorganisms were often similarly distributed throughout the lake, apparently forming distinct ecological networks. 

The scientists ran a computational simulation of the biogeochemistry of the lake and these networks aligned with the distribution of metabolic processes predicted by said simulation.

However, genetic tests revealed that only some of the microorganisms in the networks could carry out these processes. Based on this, the researchers believe the networks are consortia of taxonomically diverse and metabolically different microorganisms that group together at different depths to exploit particular resources.

Microbial communities such as these can play a major role in eutrophication, a form of inland water pollution that eventually leads to plants competing for sunlight and depleting oxygen. 

“Capturing the dynamics of the microbial processes and organisms mediating them is the first step towards engineering solutions to these problems and predicting the response to both man-made and natural changes to the system,” says Preheim, now at Johns Hopkins University.

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