Effect of methyl viologen and oxygen concentration on thermophilic bacteria.

The level of superoxide dismutase, catalase, and peroxidase was determined in obligately thermophilic bacteria after growth either in the presence of methyl viologen (paraquat) or exposed to an increased atmospheric oxygen concentration. In general, the superoxide dismutase level in these organisms was not altered by paraquat addition and had a varied response to oxygenation. Incorporation of paraquat in the growth medium resulted in minimally three-fold higher levels of catalase. The peroxidase level varied as a response to oxygen stress whereas cellular catalase levels were generally higher.