The role of dissimilatory Fe(III)-reducing bacteria in transformation of iron minerals

The possible role of bacteria in the formation and transformation of iron minerals is considered on the basis of the Recent biogeochemical cycle of iron. Dissimilatory Fe(III)-reducing bacteria are the main agents in the reductive part of the cycle. These bacteria are capable of reducing iron oxides and hydroxides to magnetite and siderite. A high degree of crystallinity of the iron oxides is the most important factor preventing bacterial transformation of minerals. The main component that links the oxidative and reductive parts of the cycle is ferrihydrite (a weakly crystalline mineral). Because of its large surface area, it is the optimal acceptor for bacterial iron reduction.