Effect of oxygen on the growth of Clostridium butyricum (type species of the genus Clostridium), and the distribution of enzymes for oxygen and for active oxygen species in Clostridia

Clostridia are well-known obligatory anaerobic bacteria which cannot utiliz e oxygen, or otherwise die in oxygenated environments. Clostridium butyricu m, the type species of the genus Clostridium, possesses the ability to cons ume oxygen in amounts proportional to the size of the inoculum. Oxygen cons umption was observed when NADH and NADPH were added to the cell extract of this strain. NADH oxidase and NADPH oxidase activities were also detected i n all of the tested strains of the genus Clostridium. C. butyricum ceased g rowing while consuming oxygen in the medium. After consumption of all the d issolved oxygen, C. butyricum resumed growth at a rate equivalent to its an aerobic growth rate, suggesting that no oxidative damage based on oxygen re duction occurs in vivo. As scavengers for active oxygen species, the activi ties of NADH/NADPH peroxidase and SOD were detected in C. butyricum. Furthe rmore, the activities of these enzymes are distributed widely in the genus Clostridium.