Manganese(IV) oxide has strong sorption affinity and oxidizing property for various elements, which govern their fate in the environment. It is well known that Mn(II)-oxidizing bacteria and fungi accelerate Mn(II) oxidation, resulting in the formation of Mn(IV) oxide. Due to strong oxidizing property, Co(II) and Ce(III) can be oxidized to insoluble Co(III) and Ce(IV), respectively, by biogenic Mn(IV) oxide. On the other hand, microbial activities affect the solubility and mobility of radionuclides. Organic ligands secreted from microbial cells can be complexed with Ce(IV) and the tetravalent actinides, Th(IV) and Pu(IV), resulting in their desorption from Mn(IV) oxide. Recently, the distribution coefficient of Ra for biogenic Mn(IV) oxide by Coprinopsis urticicola strain Mn-2 was determined to be 2.8 × 10⁷ mL/g. The reported value is very high enough to remove Ra from Ra-containing mine water in a practical use.

Biogenic Mn(IV) oxide,Radionuclides