Methanogenesis and metal leaching on anaerobic decomposition of graptolite argillite

Estonian sedimentary deposits (e.g., graptolite argillite) with relatively high content of organic matter and metals (V, Mo, U and Zn) are habitat for microorganisms. Metals exist in argillite as sulfides, in the composition of organometallic compounds or in silicate minerals. While the role of pyrite oxidizing microorganisms in bioleaching of metals is well described, less is known about the processes related to transformation of organometallic complexes. The current study examines impact of microorganisms on argillite organic matter decomposition as well as on metals leaching and/or precipitation. The microbial diversity of methane producing, and possible metal leaching consortium is described, the role of betaine in biodegradation of argillite organic matter is explained and a tentative mechanism for organic matter degradation with simultaneous methanogenesis is proposed.