Cloning of the bile salt hydrolase (bsh) gene from Enterococcus faecium FAIR-E 345 and chromosomal location of bsh genes in food enterococci.

Enterococcus faecium strain FAIR-E 345 isolated from food was shown to possess bile salt hydrolase (Bsh) activity in a plate screening assay and by high-performance liquid chromatography analysis. The bsh gene was cloned and sequenced. DNA sequence analysis revealed that it encoded a protein of 324 amino acids, with pI 4.877. A bsh gene probe was prepared from the cloned bsh gene and was used for probing plasmid and total genomic DNA of Bsh-positive enterococci isolated from food to determine the genomic location of their bsh genes. This probe was able to detect the bsh gene among total genomic DNA preparations but not from plasmid preparations of 10 plasmid-bearing Enterococcus strains. However, the probe could detect the bsh gene from total genomic DNA preparations of 12 Enterococcus strains that did not contain detectable plasmid DNA. In no cases did the probe hybridize with plasmid DNA preparations, suggesting that the bsh gene among enterococci is probably generally chromosomally encoded. This presumptive chromosomal location of bsh genes among food enterococci suggests that transfer of this trait by conjugative plasmids is unlikely. Bile acids are synthesized de novo from cholesterol and are conjugated in the liver to either taurine or glycine via an amide bond at the carboxyl C-24 position (21). The conjugates are secreted into the intestine, where the amino acids may be released from the conjugated bile acid by bacterial conjugated bile salt hydrolases (Bsh) (6, 15, 21). Bsh activity has been described for members of several bacterial genera, including Listeria, Bifidobacterium, Clostridium, Bacteroides, Lactobacillus,and Enterococcus (1‐3, 9, 10).