The effect of bile salts on survival and morphology of a potential probiotic strain Lactobacillus acidophilus M92

Bile tolerance is an important criterion in the selection of microbial strains for probiotic use. The survival and morphological changes of a potential probiotic strain, Lactobacillus acidophilus M92, in the presence of bile salts were examined. Lactobacillus acidophilus M92 has shown a satisfactory degree of tolerance against oxgall and individual bile salts tested, especially to taurocholate. The higher resistance of L. acidophilus M92 against taurine-conjugated bile salts relative to deconjugated and glycine-conjugated bile salts was attributed to its reaction to the stronger acidity of the former. Furthermore, bile salt hydrolase (BSH) was active when L. acidophilus M92 was grown in the presence of sodium taurocholate. The rate of BSH activity was highest at the exponential growth phase. It was hypothesised that BSH activity may be important for the bile salt resistance of this strain. The colonial and cellular morphology may also be a valuable parameter in the selection of bile salt-resistant Lactobacillus strains for probiotic use. Smooth (S) and rough (R) colonies, appeared in the original L. acidophilus M92 bacterial culture and demonstrated a different degree of bile tolerance. Rough colonies were more sensitive to bile salts than smooth ones. The R colony cells assumed a round form, probably induced by gaps in the cell wall caused by the cytotoxicity of glycodeoxycholate.