A transferable plasmid associated with AS-48 production in Enterococcus faecalis.

Enterococcus faecalis S-48 produces a peptide antibiotic, AS-48, and a bacteriocin, Bc-48. We have isolated mutants that lack these inhibitory characteristics. Further analysis of the mutants indicates that a plasmid of 56 kilobases (pMB2) may harbor the genes for AS-48. In conjugation experiments, pMB2 has been transferred into a plasmid-free OG1X strain of E. faecalis. The OG1X(pMB2) transconjugant produces the antibiotic AS-48 in solid medium, and the MIC of AS-48 for this strain is the same as that of the donor strain.