Aerobic and Anaerobic Bacterial Respiration Monitored by Electrodes

Abstract

A technique is described by which O2 and nitrate (or nitrite or chlorate) levels were continuously monitored during bacterial respiration. Paracoccus (Micrococcus) denitrificans and Escherichia coli oxidizing succinate rapidly ceased to reduce nitrate when O2 was available and equally rapidly commenced nitrate reduction when all the O2 was consumed. Membrane vesicles isolated from P. denitrificans reduced O2 and nitrate simultaneously. The respiratory nitrate reductase in intact cells of P. denitrificans appeared to be inaccessible to chlorate present in the reaction medium, and the nitrate reductase is probably orientated on the plasma membrane so that nitrate gains access from the inner (cytosolic) face.