Electron transfer from acetate to the surface of MnO2 particles by a marine bacterium

Abstract

Intact cells of marine pseudomonad strain BIII 88, grown in the presence of added MnSO4 (induced cells), reduced MnO2 aerobically and anaerobically with acetate. They did not reduce limonite (FeOOH) with acetate. Spectrophotometric evidence of respiratory pigments in the cell envelope and inhibition of MnO2 reduction by antimycin A and NQNO indicated that a respiratory process was involved. Stimulation of MnO2 reduction by the oxidative phosphorylation uncouplers CCCP and 2,4-DNP indicated energy conservation during the reduction. Intact cells of strain BIII 88 grown in the absence of added manganese (non-induced cells) showed marginal MnO2-reducing activity. Cell envelope fractions from induced cells prepared with a French press exhibited higher specific MnO2-reducing activity on average than those prepared by sonication. Cell envelope fractions from induced cells contained more manganese than cell envelope fractions from non-induced cells. Recombined cell fractions from induced cells were more active than recombined cell fractions from non-induced cells. MnO2 reducing activity was correlated with manganese content in cell envelope fractions. Cell envelope fractions from two cultures that do not reduce. MnO2 contained less manganese in their cell envelope fractions than similar fractions from non-induced strain BIII 88. Manganese in the cell envelope of strain BIII 88 appears to play a role in the transfer of reducing power from respiration on acetate across the cell envelope to the surface of MnO2 particles.