Development of a differential medium for bile salt hydrolase-active Lactobacillus spp.
An agar plate assay was developed to detect bile salt hydrolase activity in lactobacilli. On Lactobacillus-selective MRS or Rogosa SL medium supplemented with taurodeoxycholic, taurocholic, or taurochenodeoxycholic acids, bile salt hydrolysis was manifested at two intensities: (i) the formation of precipitate halos around colonies or (ii) the formation of opaque granular white colonies. Sixty-six lactobacilli were tested for bile salt hydrolase activity by both the plate assay and a sensitive radiochemical assay. No false-positive or false-negative results were detected by the plate assay. Based on results of experiments with Eubacterium lentum and Bacteroides species, the plate assay was dependent on two factors: (i) the presence of bile salt hydrolytic activity and (ii) the ability of the organism to sufficiently acidify the medium to protonate free bile acids. The availability of a differential medium for determination of bile salt hydrolase activity will provide a rapid method for determining shifts in a specific functional activity of intestinal Lactobacillus species and provide a rapid screening capability for identifying bile salt hydrolase-deficient mutants. The latter application should allow bile salt hydrolase activity to be used as a marker enzyme in genetic experiments.
Dashkevicz
M P
MP
Department of Growth Biochemistry & Physiology, Merck Sharp & Dohme Research Laboratories, Rahway, New Jersey 07065-0900.
Feighner
S D
SD
D000581:Amidohydrolases / Q000378:metabolism*; D000818:Animals; D002855:Chromatography, Thin Layer; D003470:Culture Media; D006868:Hydrolysis; D007778:Lactobacillus / Q000201:enzymology* / Q000254:growth & development
D003470:Culture Media; D000581:Amidohydrolases; C023154:choloylglycine hydrolase