The oxidation of manganous ions under acid conditions by an acidophilous actinomycete from acid soil

Abstract

A Stveptomyces sp. capable of oxidizing manganous ions in soil agar to manganese oxide over the pH range 5-6.5 was isolated from an acid (pH 5.0) soil. The organism failed to grow on organic media above pH 6.5 and had a pH optimum for growth of 5-5.5. On acid media its growth was restricted by manganous ions, and these were deposited as the oxide some distance from the colonies. It is suggested that the function of manganese oxidation is to protect the organism from inhibiting levels of manganous ions. The organism produced, under acid conditions (pH 5.0) in the presence or absence of added manganous ions, a water-soluble extracellular substance that could rapidly oxidize manganous ions to manganese oxide. These observations are discussed in relation to the manganese status of acid soils.