Biotransformations of manganese.

The redox properties of manganese (Mn), make it central to a variety of biological processes and result in significant and often rapid biogeochemical cycling that is mediated by abiotic and biotic oxidation and reduction, biological uptake, and mineral formation. In nature Mn occurs in three different oxidation states, +II, +III, and +IV. Mn(III) and Mn(IV) are found in environmentally prevalent ferromanganese (oxyhydr)oxide minerals, which often occur as layer-type or tunnel-structure minerals. As biotic and abiotic processes both play important roles in the oxidation and reduction of Mn, a major challenge to understanding Mn biotransformations is the differentiation and subsequent quantification of the biotic and abiotic components of the processes. Total manganese concentrations are facilely measured by using the formaldoxime colorimetric technique. In general, two considerations are important for the assays. First, the Mn(II) concentration utilized must not inhibit biological activity. Second, effective abiotic controls must be employed to distinguish biological Mn(II) removal and/or oxidation from the adsorption and autocatalytic oxidation of Mn(II) on Mn oxide surfaces. The assay proceeds with few modifications to the leucoberbelin blue (LBB) and formaldoxime methods and can be scaled to different volumes, Mn concentrations.