Rational selection and Characterisation of bile acid (BA) metabolising species of infant origin

Bile acids (BAs), biological detergents for nutrient digestion, are important local and systemic signalling molecules to interact with a variety of cell receptors central to influence host responses. While BAs are synthesized in the liver, the range and diversity of bile acids available to interact with these receptors is dictated by the gut microbiota. Bile salt hydrolase (BSH) activity is one such function, it is commonly represented and highly conserved across all major bacterial phyla in the gut. Studies relating to the importance of such modifications in early life are scarce. This study highlights BA metabolism diversity by functionally isolating BA metabolizing strains and by characterizing specific classes of BSH from the formula-fed transitioning gut. Isolates were identified to species levels, in silico and in vitro characterisation of their BSH genetic content, enzyme activity and substrate specificity. One of these isolates was identified as Lactobacillus acidophilus, a species frequently applied as a probiotic whereas three of these four isolates were identified as Enterococcus avium. This particular species is not well characterized in the literature and to our knowledge this is the first report of BSH activity and assessment for probiotic potential within this class of microbes. This study indicates that microbial BA altering activity appears functionally reduced, in the formula fed infant gut.