Biochemical and genetic evidence for production of enterocins A and B by Enterococcus faecium WHE 81.

Enterococcus faecium WHE 81, isolated from cheese, has been reported to produce a bacteriocin called "enterocin 81" [J. Appl. Microbiol. 85 (1998) 521.]. Purification of "enterocin 81" was carried out using ammonium sulfate precipitation, desalting on ODP-90 reverse-phase column, and purification through SP Sepharose HP cation exchange and C2/C18 reverse-phase chromatographies. The antimicrobial was eluted from the C2/C18 column as four individually active fractions, designated A81, B81, C81 and D81. The purification procedure used proved particularly efficient for the bacteriocin in fraction D81, with a yield of 46%, while only 3.8% the bacteriocin in fraction B81 could be collected. MALDI-TOF mass spectrometry of the bacteriocins in fractions B81 and D81 showed respective masses of 4,833.0 and 5,462.2 Da. Amino acid sequencing of the two peptides revealed two class-II bacteriocins whose sequences were similar to those of enterocin A and enterocin B, respectively. Using proper primers, chromosomal fragments of 212 and 216 bp enclosing bacteriocin structural genes were PCR-amplified. Cloning of the amplicons and their sequencing revealed two genes with sequences identical to the structural genes of enterocins A and B, respectively. It was therefore clearly established that E. faecium WHE 81 produces bacteriocins respectively identical to enterocins A and B. Our results, combined with data from previous reports, suggest that the two bacteriocins may be widespread among enterococcal strains and may play an important role in controlling the growth of pathogens and other undesirable bacteria in certain fermented food products.