Basalt rock, Wikipedia, in the public domain
Read aloud Deserts, ice landscapes or the deep sea - life has conquered the most bizarre niches on our planet, the conditions are still so hard. However, researchers now report a habitat that seems almost unimaginable: it lies beneath the sediments of the ocean floor in the rocks of the oceanic crust. Under extreme pressure and heat, microorganisms that derive their life force from chemical reactions have been shown by Mark Lever from the Danish Aarhus University and his colleagues. Although the existence of life in the plutonic rocks was already known in principle, the scientists have now directly demonstrated the microorganisms and their fascinating diet. Sampling the researchers was a truly spectacular undertaking: from a ship, a drill pipe protruded to a depth of 2.5 kilometers and hundreds of meters through the sediments into the basalt of the oceanic crust off the west coast of North America. A sterilized core drill took the rock samples here, extracted them to the surface, and finally got them to the lab of Lever and his colleagues. The researchers had to be extremely careful that the samples were not contaminated with microorganisms of seawater or the earth's surface.

The laboratory assays disclosed genetic material of microorganisms in the material and evidence that it was exposed to chemical degradation processes associated with the so-called chemosynthesis of bacteria. But this was not yet a direct demonstration of the living beings themselves. These were the first results of the scientists' laboratory experiments in the laboratory: They stimulated the microorganisms of the rock to grow by imitating their living conditions as well as possible. 65 degrees Celsius and a substrate that corresponds to basalt, through which the special deep water seeps, brought the success, Lever and his colleagues report: they were able to demonstrate the microbial production of methane.

The largest ecosystem on earth

"This provides the first direct evidence of life in the oceanic crust, and our findings suggest that this vast ecosystem is largely based on chemosynthesis, " Lever summarizes. According to the researchers, there are fine cracks in the basaltic oceanic crust through which water moves. Its chemical composition is fundamentally different from seawater, for example, it is free of oxygen produced by photosynthesis. Presumably, this deep water reacts with reduced iron compounds in the rock, releasing hydrogen, the scientists explain. "He can use the microorganisms as an energy source to convert carbon dioxide into organic material, " explains Lever. This in turn forms the basis for the nutrition of other microorganisms, because the basalt is the home of many different microorganisms, the scientists report. display

The deep ecosystem is thus completely independent of the sun's energy, which enables life on the earth's surface through photosynthesis. Plants, algae and a few other photosynthetic organisms use sunlight to convert carbon dioxide into organic matter. It forms the basis of the food chains on Earth and in the oceans. Life in the porous rocks of the oceanic crust, on the other hand, is fundamentally different: the driving force of life comes from geochemical processes, the researchers emphasize. The oceanic crust covers 60 percent of the earth's surface. This is the largest ecosystem on earth. All of these findings allow researchers to even look into the universe from the depths of the Earth: "It is possible that other planets also have life based on chemosynthesis, " says Lever.

Mark Lever (Aarhus University) et al .: Science, doi: 10.1038 / nature12017 © science.de - Martin Vieweg

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