CYTIDINE PRODUCTION BY MUTANTS OF BACILLUS-SUBTILIS

Cytidine-producing mutants were derived from Bacillus subtilis No. 122. Strain CD-300, a cytidine deaminase deficient derivative of strain No. 122, accumulated 0.1 mg/ml cytidine in the culture broth. Growth of CD-300 was inhibited by 6-azauracil and 5-fluorocytidine. The inhibition by 6-azauracil was reversed by added uracil, and that by 5-fluorocytidine was by cytidine. 6-Azauracil-resistant mutants were derived from CD-300. Most of the mutants accumulated both uracil and uridine. A representative strain, No. 229, accumulated 6.2 mg/ml uracil and 1.0 mg/ml uridine in the culture. Subsequently, 5-fluorocytidine-resistant mutants were derived from No. 229. Among them, strain No. 344, which was resistant to 500 mu g/ml 5-fluorocytidine, accumulated 10.4 mg/ml cytidine in the culture broth.