Hydrogenotrophic metabolisms in the subsurface: Utilizing reducing power from the deep Earth.

CASCONE M; BASTIANONI A; CORDONE A; DI LORIO L; CORREGGIA M; BARRY P.; LLOYD K.; JESSEN G.; AGOSTINA CHIODI; DE MOOR M.; SCHRENK M; LACONO R; MORACCI M; GIOVANELLI D.

Workshop; Understanding oxygen fugacity in Geosciences International School.; 2022

Hydrogen is a fundamental electron donor in diverse microbial metabolisms and it is considered theenergetic currency exchanged within microbial communities in anaerobic environments. Hydrogen isalso considered one of the keys to a greener energetic society. In geological settings hydrogen can beproduced by a variety of different processes, including serpentinization and metasomatism. Whenhydrogen is released from depth, it travels toward the surface traversing a large subsurfaceecosystem. Microbial communities present in the subsurface are able to utilize hydrogen in differentways, coupling its oxidation to the reduction of a variety of different compounds. Hydrogen utilizationin microorganisms is performed through a diverse group of enzymes called Hydrogenases, thatcatalyze the oxidation of molecular hydrogen to protons and electrons. These diverse enzymes usetangled organometal complexes built around a binuclear Ni-Fe, Fe-Fe or Fe center, with bound COand CN(-) groups, as well as multiple FeS centers. Understanding the diversity of Hydrogenases inthe subsurface and the role of the availability of different trace elements in controlling their distributionis crucial to understand the microbial utilization of reducing power derived from geological reactions.Here, I will present data on the diversity of hydrogenases from a number of deeply-sourced springsfrom the Argentina backarc. The results will help to establish the baseline of hydrogenotrophicmetabolisms in the subsurface, complementing our knowledge of volatile cycling by microorganismsand understanding the redox balance of our planet.