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 stra ins for probiotic use. The survival and morphological changes of a potentia l 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, espec ially to taurocholate. The higher resistance of L. acidophilus M92 against taurine-conjugated bile salts relative to deconjugated and glycine-conjugat ed bile salts was attributed to its reaction to the stronger acidity of the former. Furthermore, bile salt hydrolase (BSH) was active when L. acidophi lus M92 was grown in the presence of sodium taurocholate. The rate of BSH a ctivity was highest at the exponential growth phase. It was hypothesised th at BSH activity may be important for the bile salt resistance of this strai n. The colonial and cellular morphology may also be a valuable parameter in the selection of bile salt-resistant Lactobacillus strains for probiotic u se. Smooth (S) and rough (R) colonies, appeared in the original L. acidophi lus M92 bacterial culture and demonstrated a different degree of bile toler ance. Rough colonies were more sensitive to bile salts than smooth ones. Th e R colony cells assumed a round form, probably induced by gaps in the cell wall caused by the cytotoxicity of glycodeoxycholate.