ISOLATION AND CHARACTERIZATION OF A HYDROGEN-PEROXIDE RESISTANT MUTANT OF BACILLUS-SUBTILIS

A mutant of Bacillus subtilis has been isolated by continuous selectio n in increasing concentrations of H2O2. It grew with a doubling time o f 85 min in minimal medium containing 150 mM H2O2, whereas the wild-ty pe parent lysed in 100 mM H2O2. The mutant was also more resistant to organic peroxides than the wild-type. Further resistance to H2O2 could not be induced by pretreatment with low concentrations of the oxidant . The mutant synthesized a number of proteins at a much higher rate th an the wild-type, including constitutive synthesis of all of the prote ins which were induced by H2O2 in the wild-type. Four of these protein s were sequenced; three were identified as catalase and two subunits o f alkyl hydroperoxide reductase. Two proteins whose synthesis was repr essed in the mutant were sequenced, and one was identified as flagelli n. The mutant grew as non-flagellated, partially septate, filaments of cells, and fragments of flagella were seen in the surrounding medium.