Cytochrome content in Azospirillum brasilense Sp 7 grown under aerobic and denitrifying conditions

Abstract

Azospirillum brasilense Sp 7 was grown in batch cultures with O2, [Formula: see text], [Formula: see text], or N2O as final electron acceptor. There were marked differences in cytochrome composition depending on the O2 status of the culture and the electron acceptor utilized. Highly aerated cultures showed no [Formula: see text] reduction and the cytochrome composition (a soluble c-type and particulate aa3, b, and c cytochromes) was not affected by the presence of[Formula: see text]. Under low aeration, in the presence of [Formula: see text], nitrate reductase activity occurred and there was a significant increase in the soluble and particulate cytochromes. Particulate cytochrome b-556 was observed only under high aeration and the cytochrome aa3, observed under both high and low aeration, decreased as the O2 concentration decreased. A particulate CO-binding cytochrome of type o was observed in the cells grown under high aeration. Cytochrome cd nitrite reductase was observed only in the soluble fraction of [Formula: see text]-grown cultures, which also contained the highest concentrations of the soluble cytochrome c-548 and the particulate c-551. N2O-grown cultures showed b-560 and c-551 cytochromes in the particulate and the c-548 cytochrome in the soluble fraction.