A bacteriocin-mediated antagonism by Enterococcus faecium BC25 against ruminal Streptococcus bovis

A bacteriocin-like activity produced by Enterococcus faecium BC25, isolated from the rumen of a cow, was partially purified and characterized. The act ive substance was prepared by ammonium sulfate and chloroform/methanol prec ipitation of culture supernatant. The bacteriocin was a protein of molecula r mass 17.5 kDa. Activity was inactivated by trypsin and proteinase K. The bacteriocin BC25 inhibited growth of amylolytic ruminal strains of Streptoc occus bovis, including S. bovis AO 24/85. Results showed that bacteriocine substance BC25 has a bacteriostatic effect when present in concentrations e xceeding 125 AU/ml. Agar overlays and batch culture growth experiments prov ed that E. faecium BC25 was producing bacteriocin that inhibited the growth of S. bovis.