The effect of nutrients on the growth and manganese oxidation of fungi and bacteria

Background/Question/Methods

Metal-laden acidic mine drainage from abandoned mines contributes immensely to pollution of watersheds throughout the Appalachian region. Metals, such as manganese, can be removed via passive treatment systems, in which microbiological activity has been shown to catalyze the attenuation of these metals, especially manganese. Diverse fungi and bacteria are able to oxidize manganese although the reasons for biological manganese oxidation and what factors influence it are not well known. In this study, we grew four fungal species (Plectosphaerella cucumerina, Acremonium strictum, Pyrenochaeta sp. and Stagonospora sp.) and three bacterial strains (Falls 11, AST1-a1AYC and AST2-a2AYBbac) on solid and liquid media, respectively, containing Mn²⁺ and different concentrations of three carbon and two nitrogen sources and observed rates of growth and manganese oxidation in order to investigate the role of nutrition in these phenomena.

Results/Conclusions

While the bacterial isolates exhibited little, if any, growth and absolutely no manganese oxidation, the fungal species exhibited a wide array of growth and oxidation rates. Plectosphaerella cucumerina had the highest rates of growth and Acremonium strictum oxidized manganese in more media than the other fungi, but overall the results were highly varied. P. cucumerina was found, however, to raise the pH of its surroundings in order to facilitate the oxidation of manganese. We concluded that different species of fungi and bacteria have different nutritional requirements for successful growth and manganese oxidation, and it is possible that fungi and bacteria have evolved different pathways by which to oxidize manganese.