REDUCTION OF FERRIC HYDROXIDE BY STRAINS OF BACILLUS POLYMYXA

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Abstract
When a suspension of clay particles is incubated in 0.5% glucose soln., an enrichment culture of B. polymyxa develops which reduces ferric oxides very rapidly. The organism can be isolated by streaking such an enrichment culture over the surface of a glucose-clay suspension medium containing 2% agar and incubating anaerobically for one week at 30[degree]C. Colonies of the species sought appear blue. Cultures isolated in this way reduce up to 150 mg. of iron during 24 hrs.'' incubation. In the presence of glucose, resting cells actively reduce dialyzed ferric hydroxide at pH 7.2. The fermentation of glucose is accelerated in the presence of ferric hydroxide and the ratio of CO2 to H2 produced is considerably increased.