Discovered a decade ago, that life seems to have nothing intraterrestrials anecdotal: it could represent half of the biomass the globe, as much organic carbon than what is found on the surface of the Earth. Recent studies on the sediments and oceanic basalts show that we can identify a large number of species adapted to very unique physiological and biochemical characteristics. To thrive, the ecosystems in these environments derive their metabolic energy from hydrothermal fluids that flow directly or mineral rocks, altering. The carbon source may, in turn, completely inorganic case CO 2 dissolved derived from seawater or magmatic fluids deep, or be inherited more superficial level if sedimentary organic carbon.
In this perspective, the peridotite of the oceanic lithosphere are of particular interest. Indeed, during their interaction with sea water, these rocks have the potential to generate significant amounts of hydrogen, fuel for the living, and this through the hydration reaction of magnesium silicates and iron (olivine, pyroxene). This hydrogen combined with carbon dioxide, could be the basis of community development chimiolithoautotrophes say, first step of these ecosystems intraterrestrials. At higher temperature, if this hydrogen reduced CO 2 , serpentinization may also be accompanied by production of light hydrocarbons, particularly methane. These reactions of Fischer-Tropsch type are completely abiotic but must also be considered in these approaches because they can provide metabolic substrates for deep-sea ecosystems.
Despite the potential importance of these habitats, very few studies (Geo) microbiology have been conducted so far in these environments, compared to the systems of basaltic crust oceanic sediments associated. There is therefore no direct evidence of the existence of these microbial niches fed by the volatile mantle and many simple questions remain unresolved: how can the extent of microbial colonization, its nature and participation rate? depths to which these systems develop? how long that life continues after that hydrothermal activity has declined and that the rock has aged? What extreme physical and chemical properties are able to tolerate these microorganisms? what may be the primary productivity of microbial populations in these environments ? what are the physicochemical factors that limit the productivity? what role these microorganisms in carbon sequestration, the elemental recycling between the ocean and the crust and the geological evolution of the lithosphere? they constitute an interesting way to understand how there are more than 3 billion years, life appeared on Earth Archean inhospitable?
is to search for signs of microbial presence in hydrated peridotites of oceanic lithosphere that Geomicrobiologists the IPGP and the Università di Modena e Reggio Emilia (Italy) joined the team SMOOTHSEAFLOOR. While on board most of the work is appropriately packaged samples with minimal risk of contamination, back to the laboratory, many techniques of spectroscopy and microscopy will be implemented to search for relics of these rocks an increased microbial activity (presence of biological molecules or biominerals). This will lay the foundations for the functioning of microbial ecosystems in these environments ultramafic yet little explored, to assess their possible role in the processes of silicate weathering mantle and crystallization of new phases and their potential impact in global biogeochemical cycles.
