Partial purification and characterization of manganese-oxidizing factors of Pseudomonas fluorescens GB-1

The Mn2+-oxidizing bacterium Pseudomonas fluorescens GB-1 deposits Mn oxide around the cell. During growth of a culture, the Mn2+-oxidizing activity of the cells first appeared in the early stationary growth phase. It depended on the O-2 concentration in the culture during the late logarithmic growth phase. Maximal activity was observed at an oxygen concentration of 26% saturation. The activity could be recovered in cell extracts and was proportional to the protein concentration in the cell extracts. The specific activity was increased 125-fold by ammonium sulfate precipitation followed by reversed-phase and gel filtration column chromatographies. The activity of the partly purified Mn2+-oxidizing preparation had a pH optimum of circa 7 and a temperature optimum of 35 degrees C and was lost by heating. The Mn2+-oxidizing activity was sensitive to NaN3 and HgCl2. It was inhibited by KCN, EDTA, Tris, and o-phenanthroline. Although most data indicated the involvement of protein in Mn2+ oxidation, the activity was slightly stimulated by sodium dodecyl sulfate at a low concentration and by treatment with pronase and V8 protease. By polyacrylamide gel electrophoresis, two Mn2+-oxidizing factors with estimated molecular weights of 180,000 and 250,000 were detected.