Electron Transfer Coupled to Mn(II) Oxidation in Two Deep-Sea Pacific Ocean Isolates

The abilities of a number of different bacteria to couple the oxidation of manganous manganese to the generation of useful energy have been reviewed (Ehrlich, 1978). The oxidation of manganese is believed to occur via the action of a Mn(II)-oxidoreductase, which catalyzes the transfer of electrons from manganese to the electron transport system of the cell. The electron transport system involved in this transfer of electrons has not been thoroughly explained. However, in the case of the soil bacterium Leptothrix discophora, it was found that cell-free, manganese oxidizing particles contained both b-type and c-type cytochromes, as well as a cytochrome oxidase (Hogan, 1973). Manganese oxidation by these particles was completely inhibited by 10−5 M KCN and 10−4 M NaN₃. The inhibition by CN− and N₃− and the results of spectral studies indicated the involvement of a cytochrome oxidase in Mn(II) oxidation. The involvement of the b-type or c-type cytochromes was not shown.