Investigation of microbial-mineral interactions by Mossbauer spectroscopy

Mossbauer spectroscopy was used to investigate the reactions of microbes wi th iron minerals in aqueous solutions and as components of rocks in banded iron formations and granite. A microbial biofilm that formed on a wall of a n excavated granite vault in a deep underground laboratory initiated this r esearch. At the aerobic face of the biofilm, iron was found in a form of fe rrihydrite; in the anaerobic face against the rock, iron was found as very small siderite particles. Laboratory incubations of the biofilm microbial c onsortium showed different mineral species could be formed. When the microb ial consortium from the biofilm was incubated with magnetite grains, up to about 10% of the iron was altered in three weeks to hematite. The ability o f the consortium to precipitate iron both as Fe2+ and Fe3+ in close proximi ty may have a bearing on the deposition of banded iron formations. These re actions could also be important in microbially induced corrosion.