Social Oil Microbes Exchange Genes Deep Within the Earth

Oil reservoirs can be found deep within our planet, scattered across Earth. Because of this, you might think that the underground organisms that dwell within this oil are completely different. Yet scientists have now found that these microbes are actually social creatures that have exchanged genes for eons.

Scientists are continually discovering a growing number of microbial life forms deep underground. Yet exactly how these organisms came to inhabit these locations has long remained a mystery. They feed off of chemical and nutrients where temperatures and pressures are extreme.

In order to learn a bit more about these underground organisms, the researchers analyzed 11 genomes of Thermotoga, an ancient lineage of heat-loving bacteria, taken from oil reservoirs in the North Sea and Japan and from hot water vents on the ocean floor near the Kuril Islands north of Japan, Italy and the Azores. The researchers also analyzed Thermotoga community DNA from the environment from North America and Australia.

In the past, researchers supported a "burial and isolation" scenario in which bacteria living in oil reservoirs are descendants of isolated bacterial communities buried with sediments that, over time, become oil reservoirs. Yet this latest research hints that this isn't the case.

"Instead, our analysis supports a more complex 'colonization' view, where bacteria from subsurface and marine populations have been continuously migrating into the oil reservoirs and influencing their genetic composition since ancient times," said Olga Zhaxybayeve, one of the researchers, in a news release.

The researchers actually discovered that there was extensive gene flow across all of the sampled environments. This, in particular, suggests that bacteria do not stay isolated in oil reserves. Instead, it's possibley that they have long migrated to and colonized the reservoirs and contributed to their genetic make-up.

"The pathway of the gene flow remains to be explained, but we hypothesize that a lot of the gene flow may happen within the subsurface," said Camilla Nesbo, co-author of the new study.

The findings are published in The ISME Journal.

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