Relationship between bile salt hydrolase activity, changes in the internal pH and tolerance to bile acids in lactic acid bacteria

Abstract

To evaluate bile salt hydrolase activities, changes in the internal pH and cell survival to bile acids in lactic acid bacteria to establish the relationship between these parameters.

Genetic Characterization and Gene Expression of Bile Salt Hydrolase (bsh ) from Lactobacillus reuteri CRL 1098, a Probiotic Strain

“…The highest affinity observed by the glycoconjugated substrates is consistent with our previous results [39,38], as well as for numerous choloylglycine hydrolase enzymes described in the literature [19], which could be related to the higher toxicity of glycine-conjugated BA respect to taurine-conjugated BA [6]. Although the precise mechanism is unknown, the capability to hydrolyze BA may contribute to the survival and persistence of bacterial strains in the intestinal tract, as was previously suggested by many authors [19,39,1]. Since deconjugated BAs display reduced solubility compared to their conjugated counterparts, especially at lower pH values, BA hydrolysis may lead to precipitation of the BA and thus may reduce the damage caused by these compounds.…”

Intestinal transport and metabolism of bile acids

“…Indeed, another prevailing hypothesis is that the gut bacteria metabolize bile acids to thwart this host defense, thereby gaining an advantage over competing microbes ( 157,163 ). Mechanisms responsible for the antimicrobial actions of bile acids have been investigated and include direct interaction with cell membranes ( 164 ), with protonated unconjugated bile acid species having more potent effects than conjugated species ( 161,165 ), acidifi cation of the cytoplasm ( 166 ), and induction of DNA damage ( 161 ). A detergent role for mixed micelles of conjugated bile acids and dietary long chain fatty acids derived from the digestive process has also been proposed to explain the antimicrobial actions of endogenous and exogenously administered conjugated bile acids ( 159 ).…”

The Lactobacillus casei Group: History and Health Related Applications

“…BSH activity has been found in L. casei but is not always present ( Gilliland and Speck, 1977 ; Zhang et al, 2009 ; Wang et al, 2011 ). There is conflicting evidence whether or not BSH increases tolerance to bile salts with many studies finding a correlation ( Moser and Savage, 2001 ; Wang et al, 2011 ) while many others have failed to find correlation between BSH activity and bile tolerance ( Begley et al, 2005 ; Bustos et al, 2012 ).…”