MANGANOUS ION OXIDATION AT PH VALUES BELOW 5.0 BY CELL-FREE SUBSTANCES FROM STREPTOMYCES-SP CULTURES

Liquid cultures of a soil Streptomyces sp. produced extra-cellular, non-dialysable substances which when mixed with 0.5 mM manganese sulphate precipitated manganese oxide. Quantitative studies on the rate of manganese oxidation showed that these substances were unique since their optimum pH for oxidation was about pH 5.0 and they were unable to oxidize manganese at pH 6.5-7.5. Oxidation was also completely inhibited at pH 4.0 but not at pH 4.5. The active substances were only detected in liquid cultures that were at least 4 weeks old. These cultures also contained lower molecular weight substances that inhibited oxidation but these were readily removed by dialysis or ultra-filtration. © 1979.