While working on the bottom of the Indian Ocean off the coast of Africa, oceanologists found microbes that live in rocks at a depth of 700 meters below the bottom surface. Scientists published an article describing the findings in the scientific journal Nature.
"We have discovered an extremely small, but quite viable and active community of microbes that live in the thickness of the oceanic crust. This discovery greatly expands our understanding of how far the boundaries of the Earth's biosphere extend," the scientists write.
In the recent past, biologists assumed that life exists only on the surface of the planet, in the upper layers of water and soil, where there is enough oxygen, trace elements and nutrients. Over the past two decades, scientists have found many signs that the boundaries of the biosphere are noticeably wider.
In particular, oceanologists have found large colonies of microbes at the bottom of the Mariana Trench, as well as in the mass of terrestrial rocks that have been excavated from a depth of several kilometers. Moreover, zoologists have discovered several types of "underground" multicellular animals, including millipedes and nematode worms, which live in the lower parts of many kilometers of caves and mines.
One of the most unusual features of these creatures is their very slow metabolic rate. This is due to the constant lack of nutrients. Because of this feature, such organisms are much more difficult to study, since scientists have to very accurately reproduce the conditions in which they live.
Secrets from the bottom
A group of oceanologists led by Virginia Edgecomb, professor at the Woods Hole Oceanographic Institute, has once again "expanded" the boundaries of the Earth's biosphere. Studying the rocks of the crust, mined from the slopes of the Atlantis Ridge at the bottom of the Indian Ocean in early 2016, they found an unusual ecosystem of "underground" microorganisms.
When geologists found bacteria inside samples of the continental crust, Edgecomb and her colleagues wondered if microbes could be found in its marine counterparts with slightly different mineral and chemical composition. Guided by this idea, scientists obtained several samples of the earth's crust from the bottom of the Indian Ocean, crushed them and tried to find scraps of RNA and other biomolecules.
To their great surprise, in all samples of rocks, including those mined from a depth of 700 meters from the bottom of the ocean, similar traces of microbes were found - in small but stable quantities. Having studied the structure of individual fragments of RNA, as well as fats and proteins, the scientists made a kind of "census" of these microbes.
It turned out that a full-fledged ecosystem was formed in the deep rocks of the marine earth's crust, in which both archaea and bacteria lived, which can extract energy from various inorganic compounds, and microbes that feed on ready-made organic matter. Moreover, scientists have found and even raised several types of fungi that live inside these rocks along with bacteria.
All these organisms, as Edgecombe noted, were united by the fact that they use resources very economically. They have developed a whole set of methods thanks to which you can reuse your spent protein molecules and other compounds that play an important role in the life of cells.
The study of these bacteria and fungi, according to scientists, will help not only to clarify the size of the biosphere and the total mass of all life on Earth, but also to understand where the first representatives of extraterrestrial life on the planets of the solar system and beyond can "hide".