Oxygen caused an increase in the amount of superoxide dismutase in Escherichia coli B but not in Bacillus subtilis. E. coli B cells, induced by growth under 100% O(2), were much more resistant to the lethal effects of 20 atm of O(2) than were cells which contained the low uninduced level of this enzyme. In contrast, B. subtilis, which could not respond to O(2) by increasing its content of super...