A hydrogen peroxide resistant mutant ofSpirillum volutanshas NADH peroxidase activity but no increased oxygen tolerance

Abstract

The catalase-negative microaerophile Spirillum volutans is killed rapidly by levels of H₂O₂greater than 10 μM. A mutant isolated by single step mutagenesis with diethyl sulfate was able to survive and grow after exposure to 40 μM H₂O₂and was effective in eliminating H₂O₂added to the medium. Nevertheless, the mutant was no more colerant to O₂than the wild type. The only apparent phenotypic difference between the wild type and the mutant was that the mutant had high NADH peroxidase activity (0.072 IU^.mg^-1) whereas the wild type had no detectable activity (.mg^-1). NADH peroxidase has not previously been reported in gram-negative bacteria or in bacteria having a strictly respiratory type of metabolism.Key words: microaerophile, Spirillum volutans, peroxidase, oxygen tolerance, hydrogen peroxide.