Cytochrome Formation, Oxygen-induced Proton Extrusion and Respiratory Activity in Streptococcus faecalis var. zymogenes Grown in the Presence of Haematin

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Abstract
S. faecalis var. zymogenes was grown in O2-limited continuous culture in a lactate/tryptone/yeast extract medium containing 7.5 .mu.g hematin ml-1. Low temperature difference spectra of whole organisms and washed membranes showed 2 peaks in the cytochrome b region, at 558 nm and 562 nm, and a peak at 627 nm indicative of a d-type cytochrome. A CO-binding cytochrome was also present in the hematin-grown bacteria. These cytochromes were not detected in bacteria grown without hematin. The hematin-grown bacteria produced proton pulses in a weakly buffered medium when pulsed with O2-saturated buffer. The average .fwdarw. H+/O ratio of such pulses was 1.4 and they were abolished by carbonyl cyanide m-chlorophenylhydrazone (CCCP). The hematin-grown bacteria had a high activity of particulate NADH oxidase, at least 10 times that of bacteria grown without hematin. They also had a high lactate QO2 which was strongly inhibited by CCCP and gramicidin but bacteria grown without hematin had a very low lactate QO2 largely insensitive to the uncoupling agents. The glucose QO2 was similar in bacteria grown in the presence or absence of hematin but was stimulated by uncoupling agents in hematin-grown organisms and slightly inhibited by these agents in organisms grown without hematin. These results confirm earlier findings of the ability of S. faecalis to form a functional cytochrome system in the cell membrane when supplied with hematin and show that electron transport to O2 by such a system is coupled to proton translocation.