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

Abstract

Streptococcus faecalis var. zyrnogenes was grown in oxygen-limited continuous culture in a lactate/tryptone/yeast extract medium containing 7·5 μg haematin ml-l. Low temperature difference spectra of whole organisms and washed membranes showed two 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 haematin-grown bacteria. These cytochromes were not detected in bacteria grown without haematin. The haematin- grown bacteria produced proton pulses in a weakly buffered medium when pulsed with oxygen-saturated buffer. The average →H+/O ratio of such pulses was 1·4 and they were abolished by carbonyl cyanide m-chlorophenylhydrazone (CCCP). The haematin-grown bacteria had a high activity of particulate NADH oxidase, at least 10 times that of bacteria grown without haematin. They also had a high lactate Q 02 which was strongly inhibited by CCCP and gramicidin whereas bacteria grown without haematin had a very low lactate Q 02 largely insensitive to the uncoupling agents. The glucose Q 02 was similar in bacteria grown in the presence or absence of haematin but was stimulated by uncoupling agents in haematin- grown organisms and slightly inhibited by these agents in organisms grown without haematin. These results confirm earlier findings of the ability of S. faecalis to form a functional cytochrome system in the cell membrane when supplied with haematin and show that electron transport to oxygen by such a system is coupled to proton translocation.