Respiratory biogenesis during the cell cycle of aerobically grown Escherichia coli K 12. The accumulation and ligand binding of cytochrome o.

A quantitative assay is described for the measurement of cytochrome o in intact cells of E. coli. The procedure involves flash photolysis of the CO-liganded, reduced enzyme in the absence of O2 at temperatures (approx. -100 degrees C) at which the rate of recombination of CO is immeasurably slow. Other CO-binding pigments known to be present, particularly cytochrome d, are excluded from the photodissociation spectrum under these conditions. Measurement of the content of cytochrome o in bacteria separated into size (and thus age) classes by zonal centrifugation shows that the cytochrome accumulates continuously, probably exponentially, throughout the cell cycle and thus constitutes a constant proportion of cell protein during the cycle. The velocity of recombination of CO with cytochrome o at -65 degrees C is invariant over the cell cycle.