Most of the Earth’s microbial biomass is hidden in the subsurface. According to estimates, microorganisms can be found at depth of up to five kilometers below the continental surface. Here they also colonize solid rock. Since this deep biosphere is difficult to access, researchers know little about the composition and role of these microorganisms in biogeochemical cycles.
Click here for original story, Study shows limestone can serve as a repository of microbial genetic information about the deep biosphere
Source: Phys.org