Search

The amino acid composition and amino acid sequence of the murein (peptidoglycan) of 10 strains of planococci were studied. It is shown that the peptide subunit consists of muramyl-l-alanyl-gamma-d-glutamyl-l-lysyl-d -alanine. The cross-linking of two adjacent peptide subunits is mediated by d-glutamic acid which is bound to the epsilon-amino group of lysine by its gamma-carboxyl group and to the carboxyl group of d-alanine of an adjacent peptide subunit by its amino group. About 20 to 25% of the peptide subunits are not cross-linked. The murein structure of the different species and strains of Micrococcus, Staphylococcus, and Sarcina are compared. It is evident that the murein structure is a very good criterion for grouping the micrococci. In addition, some of these groups are fairly well defined by physiological properties as well as by their guanine + cytosine content of the deoxyribonucleic acid e.g., Micrococcus, Staphylococcus, Planococcus, Sarcina ureae. Other groups, represented by a single or a few strains only, such as M. varians NTCC 7281, M. radiodurans, M. freudenreichii ATCC 407, and M. luteus ATCC 398, need further investigation.