Abstract
The changes occurring in the respiratory enzymes of anaerobically grown Escherichia coli strain B and E. coli 15 T(-)A(-)U(-)bar during exposure to oxygen were studied. Reduced nicotinamide adenine dinucleotide (NADH) oxidase activity reached its peak soon after O(2) exposure; cytochrome content and succinate oxidase activity increased more slowly, and these increases paralleled each other. The activities of isocitrate and malate dehydrogenases also increased, but the increase was less than that of the succinate and NADH oxidases; exposure to O(2) had no effect on the succinate and NADH dehydrogenase activities. On the other hand, the glycolytic activity decreased slowly after O(2) exposure. The incorporation of (32)P into acid-soluble organic phosphate esters paralleled the respiratory rate during the first 60 min after O(2) exposure, but continued to increase after the respiration reached a plateau. The sensitivity of (32)P incorporation to the uncoupler carbonyl cyanide m-chlorophenylhydrazone also increased with time. The observed relationship between the development of the respiratory chain and the energy-conserving mechanism during O(2) exposure is discussed. Synthesis of the respiratory enzymes upon exposure to oxygen was dependent on concomitant protein and ribonucleic acid synthesis but not on deoxyribonucleic acid synthesis.