Peptidoglycan composition and taxonomy of group D, E, and H streptococci, and Streptococcus mutans

The qualitative and quantitative composition of the peptidoglycan from the cell wall of groups D, E, and H streptococci, and Streptococcus mutans, was determined. In group D, S. faecalis and the closely related species S. liquefaciens and S. zymogenes were separated from S. faecium and the closely related species S. durans on the basis of their peptidoglycan composition. A relationship among S. bovis, S. equinus, and some strains of S. mutans was indicated by the presence in each of a similar peptidoglycan containing threonine. Threonine was released from the S. mutans polymer as a threonine-lysine dipeptide. Hydrolysis of the dipeptide at 100 C for 24 hr in 6 n HC1 was required to break the peptide bond. Motile group D streptococci possessed a peptidoglycan of the same composition as S. faecium. Group E and H strains were also similar in the composition of their peptidoglycan. The results demonstrate that peptidoglycan composition can be used to (i) aid in the division of members of an immunological group into subgroups, and (ii) indicate a relationship between members of the same genus which are not related on an immunological basis.