Biotin deficiency in Nigrospora oryzae

Nigrospora oryzae is reported to be partially deficient for biotin. The external requirement for the vitamin is shown to be conditioned by the nitrogen source. The deficiency for biotin is apparent when urea or nitrate is used to supply the nitrogen. The organism is found to be more dependent on an external supply of biotin in media where autoclaved urea is the source of nitrogen than where nitrate or sterilefiltered urea is that source. Aspartic acid is found to induce a complete sparing action for biotin requirement should the nitrogen source be nitrate. Malt and yeast extracts are reported to supply probable unidentified growth promoting substances other than biotin.