Increase in arginine and citrulline production by 6-azauracil-resistant mutants of Bacillus subtilis.

In the arginine producer AHr-5, an L-arginine hydroxamate-resistant mutant of Bacillus subtilis, accumulation of N8-acetyl-L-ornithine increased as the level of L-arginine accumulation increased in the medium containing L-glutamic acid. Ornithine carbamoyltransferase of this strain was genetically derepressed. These results suggested that carbamoylphosphate might be deficient in vivo. With the intention to increase endogenous carbamoylphosphate, pyrimidine analogs inhibiting growth were selected and the mutants resistant to these compounds were derived from the AHr-5 mutant. Of the resistant mutants derived, the 6-azauracil-resistant mutant AAr-9 produced 28 mg of L-arginine per ml, which corresponded to more than twofold the amount produced by the parent strain. Derivation of an arginine-requiring mutant from the double-resistant mutant AAr-9 provides a new advantageous method for the production of L-citrulline. The increase in arginine and citrulline production is discussed.