METALS AND METALLOIDS, TRANSFORMATION BY MICROORGANISMS

Microbes possess a variety of properties that can effect changes in metal speciation, toxicity and mobility, as well as mineral formation or mineral dissolution or deterioration. Such mechanisms are important components of natural biogeochemical cycles for metals as well as associated elements in biomass, soil, rocks and minerals, e.g. sulfur and phosphorus, and metalloids, actinides and metal radionuclides. Apart from being important in natural biosphere processes, metal and mineral transformations can have beneficial or detrimental consequences in a human context. Bioremediation refers to the biological clean-up of organic and inorganic pollution with bacteria and fungi being the most important organisms in this context. In contrast, metal and mineral transformations by microbes may result in spoilage and destruction of natural and synthetic materials, rock and mineral-based building materials, acid mine drainage and associated metal pollution, biocorrosion of metals, and adverse effects on radionuclide speciation, mobility and containment. This article outlines some of the ways in which bacteria and fungi interact with and transform metals and minerals together with indications of their environmental and applied significance.