Manganese(II) adsorption and oxidation by whole cells and a membrane fraction of Pedomicrobium sp. ACM 3067

Heat treatment of Pedomicrobium sp. ACM 3067 enhanced the adsorption of Mn( II) to whole cells but abolished Mn(II)-oxidising activity. In whole cells, optimal Mn(II)-oxidising activity occurred at pH 7 and 25 degrees C. The a pparent K-m of the Mn(II)-oxidising system for Mn(II) was 26 mu M These dat a confirm that Mn(II) oxidation is an enzymic process in Pedomicrobium sp. ACM 3067. Measurement of Mn(II) oxidation during the growth cycle demonstra ted that the highest activity occulted during early- to mid-exponential pha se and was independent of the presence of Mn in the growth medium. Mn(II)-o xidising activity was localised to the membrane fraction. Transmission elec tron microscopy showed that this fraction consisted of double-layered membr ane vesicles. Positively charged molecules such as poly-L-lysine interfered with the adsorption and oxidation of Mn(II) by whole cells and membranes. Similarly, aminoglycoside antibiotics such as gentamicin sulfate proved to be potent inhibitors of Mn(ll) oxidation. Treatment of cells with the coppe r chelator diethyldithiocarbamate inhibited Mn(II) oxidation. Enzyme activi ty was restored by the addition of Cu(II) ions, but not by Co(II) nor Zn(II ). We conclude that Mn(II) oxidation in Pedomicrobium sp. ACM 3067 is catal ysed by a Cu-dependent enzyme.