The nature of epidermidins, new antibiotics from staphylococci

New antibiotics have been isolated from Staphylococcus epidermidis strains 29297 and 36534. These agents are designated epidermidins A 1 , A 2 , B 1 , B 2 and are peptides with an average molecular weight of 1200–1400 based on three independent methods of estimation. Each fraction contained 11 amino acid residues, eight of which were shared in common. The ratio of L- to D-amino acids was 7:4 for epidermidins A 2 and B 1 , while that for epidermidins A 1 and B 2 was 5:6.The appearance of the same amino acids at the beginning and end of many of the peptide fragments obtained by partial hydrolysis of epidermidin A 1 suggested that this antibiotic was a cyclic peptide. The absence of N- and C-terminal residues supported this finding. The amino acid sequence of epidermidin A 1 was also tentatively deduced and may be written as follows: cyclo-lys-ala-asp-glu-ser-leu-thr-gly-val-gly-arg.