Geomicrobiology: its significance for geology

Some microorganisms, including various kinds of bacteria, fungi, algae, and protozoa, serve as geochemical agents in the uppermost lithosphere and in the hydrosphere. Some promote rock weathering by mobilizing mineral constit uents with inorganic or organic acids or ligands that they excrete. Others promote rock weathering by redox attack of mineral constituents such as Fe and Mn. Still others cause active or passive mineral formation by precipita tion and subsequent nucleation of crystal formation on or in the cell, or i n the bulk phase. They play a role in some phases of fossil fuel formation and accumulation. They modulate the terrestrial and marine cycles of C, N, S, and P and some other elements, and they influence the composition of the atmosphere in respect to O-2, CO2, and CH4. Some discriminate between stab le isotopes of H, C, O, N, and S. (C) 1998 Elsevier Science B.V. All rights reserved.