ABSTRACT
Geologists tend to attribute observable mineral changes to abiotic processes while biologists try to explain everything in terms of biotic mechanisms (Barton et al. 2001), the actual mechanisms are often a combination of abiotic and biotic. Geomicrobiology recognizes that microorganisms are important active and passive promoters of redox reactions that can influence geological formation (Ehrlich 1996). The temporal and spatial scales of geomicrobiological processes vary greatly, from minutes to eons and microniche to global, yet the contributions made by microbes to most processes are unknown and unseen due to the very small size of a typical microbial cell. Microbes are crucial to nutrient cycling at local and global scales, able to discriminate among the stable isotopes of H, C, O, N, and S, resulting in fractionation and enrichment of lighter isotopes which are used as a marker of biological activity. Microbial activity also plays an important role in industry, being largely responsible for the production and accumulation of fossil fuels, extensive iron mineral deposits, sulfur domes, marine manganese nodules, and potentially the accumulation of uranium and gold (Ehrlich 1996, 1998).
