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 (<0.0002 IU.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.