Living deep underground ain't easy. In addition to hellish temperatures and pressures, there's not a lot to eat. Which is why oil reservoirs are the microbes’ cornucopia in this hidden realm.



Microbes feast on many oil reservoirs, but it has been unclear how the microorganisms got to those locales. One proposal has been that the microbes colonize a pool of dead algae corpses and then go along for the ride as the pool gets buried deeper and deeper and the algae slowly become oil. That’s the so-called "burial and isolation" hypothesis.



But under that set of rules each pool of oil should have its own unique microbes—and that's not the case, according to a recent study in the Journal of the International Society for Microbial Ecology. [Camilla L. Nesbø et al, Evidence for extensive gene flow and Thermotoga subpopulations in subsurface and marine environments]



Researchers surveyed the genetics of oil-eating microbes from around the world. They found that populations from Nevada to the North Sea matched up almost exactly. They also determined that microbes in the North Sea appear to have swapped genes with Japanese microbes despite the locations being more than 8,000 kilometers apart on the Earth’s surface.



These findings suggest that the deep biosphere is actually filled with connections, and that microbes move from one oil reservoir to another, colonizing them almost as soon as they form in some cases. Or it could also be that marine microbes migrate down and then evolutionary selection pressure causes a convergence in the genetics that make it possible to survive under these extreme conditions.



One thing is certain—humanity is now definitely helping this mixing of subsurface microbes, as our thirst for oil leads us to poke holes all over the planet.



—David Biello



[The above text is a transcript of this podcast.]



[Scientific American is part of Nature Publishing Group.]