[Alternative oxidation pathways in the respiratory chain of Brevibacterium flavum]

A scheme is proposed for the branched respiratory chain in Brevibacterium flavum 22 LD. Three branching sites in the main electron transport pathway are suggested: at the initial stage of NADH2 oxidation (before menaquinone) and at the levels of cytochromes b and c. Up to 40% out of the total oxygen is consumed in the NADH2-dependent alternative oxidative pathway in the presence of 5.10(-3) M cyanide or after the near UV treatment. This bypass differs from the main electron flow with a lower P/O ratio. Exogenous NADH2 catalyses the univalent reduction of oxygen through superoxide production in the bacterial membranes. Alternative oxidation pathways are discussed regarding their regulatory role in the bacterial energy metabolism.