Combinations of biotic/abiotic processes in microbe/mineral interactions

Microbial life is based on the transformations of chemical species/minerals to gain energy and to fill its needs in essential components to support its growth. Redox processes are the cornerstone of these energy or nutrient conversions by a transfer of electrons from an electron donor to a terminal electron acceptor, which may promote both mineral dissolution and biomineralisation, and/or provide reactive chemical species. When these redox processes are referred to as “abiotic” reactions, they occur spontaneously without the contribution of living microorganisms. By contrast, those so-called “biotic” pathways depend on an enzyme activity. However, the limit between abiotic/biotic processes is sometimes fuzzy and recents studies have highlighted the importance of microbially-mediated reactions especially in the formation of “biogenic” and reactive minerals. Through this seminar, emphasis will be put on three examples involving bacterial activities of nitrate, iron, and sulfate reducers which lie N, Fe and S biogeochemical cycles. Then, the relevance of unraveling microbe/mineral interactions for the interpretation of the evolution of Earth’s history as well as the developpement of applied sciences (e.g. bioremediation, bio-deterioration, biogeobattery) will be discussed.