Isolation and characterization of a hydrogen peroxide resistant mutant of Bacillus subtilis.

A mutant of Bacillus subtilis has been isolated by continuous selection in increasing concentrations of H2O2. It grew with a doubling time of 85 min in minimal medium containing 150 mM H2O2, whereas the wild-type 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 than the wild-type, including constitutive synthesis of all of the proteins which were induced by H2O2 in the wild-type. Four of these proteins were sequenced; three were identified as catalase and two subunits of alkyl hydroperoxide reductase. Two proteins whose synthesis was repressed in the mutant were sequenced, and one was identified as flagellin. The mutant grew as non-flagellated, partially septate, filaments of cells, and fragments of flagella were seen in the surrounding medium.