Assessment of bile salt effects on s-layer production, slp gene expression and some physicochemical properties of Lactobacillus acidophilus ATCC 4356.

In many conditions, bacterial surface properties are changed as a result of variation in growth medium and conditions. This study examined the influence of bile salt concentrations (0-0.1%) on colony morphotype, hydrophobicity, H2O2 concentration, S-layer protein production and slpA gene expression in Lactobacillus acidophilus ATCC 4356. It was observed that two types of colonies (R and S) were in the control group and the stress condition. When the bile level increased in the medium, the amount of S type was more than the R. A stepwise increment in the bile concentration resulted in a stepwise decline in the maximum growth rate. The results showed that hydrophobicity was increased in 0.01%-0.02% bile but it was decreased in 0.1% bile. Treatment by bile (0.01%- 0.1%) profoundly decreased H2O2 formation. S-layer protein and slpA gene expression was also altered by stress condition. S-protein expression was increased in stress condition. slpA gene expression increased in 0.01%-0.05% bile and it decreased in 0.1% bile. However, we found that different of bile salt concentrations influence on morphology and some surface properties of L. acidophilus ATCC 4356. These changes were very different in the 0.1% bile. It appears that the bacteria respond abruptly to 0.1% bile.