The Structure of manganese oxide formed by the fungus Acremonium sp. strain KR21-2

Manganese oxides are observed to form by the oxidation of aqueous solutions of Mn(II) catalyzed by the action of microorganisms. In contrast to the widely studied material produced by bacteria, manganese oxide phases produced by the action of fungi have received only limited attention.A detailed study of the MnO_x material produced by the action of the fungus Acremonium KR21-2, utilizing X-ray diffraction, XANES, EXAFS and transmission electron microscopy is reported. The MnO_x material is produced as small crystalline particles which adopt a todorokite-like tunnel structure, in striking contrast to previously reported microbial MnO_x materials which adopt layered birnessite-type structures. ICPMS measurements reveal there are no templating metal ions present in the fungally mediated MnO_x material, in contrast to analogous bacterially mediated material, suggesting these cations play a critical role in determining the structure of the material precipitated. A phylogenetic analysis places KR21-2 with other Acremonium species in the Hypocreales.