Purification and Characterization of two bacteriocins from Streptococcus faecium

Two bacteriocins were found in the supernatant fluid and in an extract of Streptococcus faecium strain EI. The small soluble enterocin EIA represented more than 90% of the total activity in the supernatant fluid, and was purified 400-fold by ammonium sulphate fractionation, gel filtration on Sephadex G-75 and chromatography on DEAE-cellulose. Enterocin EIB, with a particle weight greater than 4 x 10(6), was the predominant type in the extract. It was released in appreciable quantities after breakage of the bacteria and was purified 100-fold by differential centrifugation, chromatography on Sepharose 4B and density gradient ultracentrifugation. Enterocin EIA, a basic substance with a molecular weight of about 10000, was resistant to heat and was attacked by trypsin, whereas enterocin EIB was less thermostable and insensitive to proteolytic enzymes. The activity of enterocin EIB was unchanged by treatment with DNAase. Sensitivity to enterocin action was confined to certain strains of various enterococcus species, Streptococcus salivarius and Listeria monocytogenes; all the other Gram-positive and Gram-negative bacteria tested for sensitivity were unaffected by either enterocin.