Transfer of a miniplasmid determining bacteriocin production and bacteriocin immunity in Streptococcus faecium

Abstract Streptococcus faecium strain 3 produced a bacteriocin (enterococcin Sf3) and contained a homogeneous species of plasmid DNA (pJK3) with an M _r of 3.5 · 10⁶. Plasmid pJK3 was transferable in a filter mating procedure to S. faecium M16. The non-bacteriocinogenic strain M16 was susceptible to enterococcin Sf3 and harboured a non-selftransferable 19.1 MDa plasmid, which was responsible for erythromycin resistance. Transcipient cells of S. faecium M16 contained the 19.1 MDa and the pJK3 plasmid, produced the enterococcin Sf3 and were resistant against the inhibitory action of this bacteriocin.