Terminal oxidases of Azoarcus sp. BH72, a strictly respiratory diazotroph

The nitrogen-fixing, grass-associated bacterium Azoarcus sp. BH72 was characterized with respect to its terminal oxidases. Inhibitory respiratory analysis revealed the presence of at least one cytochrome c oxidase and one quinol oxidase. The cytochrome c oxidase was preferably used by the cells under aerobic, whereas the quinol oxidase seemed to be dominant under microaerobic, nitrogen-fixing conditions. Differential spectroscopy and heme analysis of the membrane preparations indicated that the cytochrome c oxidase is probably of the cb type.