Properties of some norvaline-resistant mutants of Bacillus subtilis

DL-Norvaline inhibits growth of wild-type Bacillus subtilis. A number of mutants resistant to growth inhibition by this analogue were isolated and studied. Cross-feeding experiments and paper chromatography of culture supernatants indicated that the mutants excreted leucine and possibly valine and glutamate. Enzymic analysis indicated that the mutants were derepressed for acetohydroxy-acid synthetase and alpha-isopropylmalate synthetase; however, no derepression of threonine deaminase, dihydroxyacid dehydrase or transaminase B was observed.