Distribution of cytochrome-like respiration in streptococci.

The electron transport systems of 134 strains of streptococci were studied after aerobic growth on glucose in the presence of haematin, by examining the inhibition of electron transport as well as the cellular site of NADH oxidation. Each strain was placed into one of three possible groups: cytochrome-like NADH oxidase; flavin-like NADH oxidase; or no NADH oxidase. Most (88%) of the strains of Streptococcus faecalis and its variants liquefaciens and zymogenes and a few strains of S. lactis and its variant diacetylactis contained cytochrome-like respiratory systems. Other streptococci including S. faecium fell into one of the other groups but did not contain cytochrome-like NADH oxidases.