Abstract
Bile acid (BA) signatures are altered in many disease states. BA metabolism is an important microbial function to assist gut colonization and persistence, as well as microbial survival during gastro intestinal (GI) transit and it is an important criteria for potential probiotic bacteria. Microbes that express bile salt hydrolase (BSH), gateway BA modifying enzymes, are considered to have an advantage in the gut. This property is reported as selectively limited to gut-associated microbes. Food-associated microbes have the potential to confer health benefits to the human consumer. Here, we report that food associated Lactobacillus plantarum strains are capable of BA metabolism, they can withstand BA associated stress and propagate, a recognised important characteristic for GIT survival. Furthermore, we report that these food associated Lactobacillus plantarum strains have the selective ability to alter BA signatures in favour of receptor activation that would be beneficial to humans. Indeed, all of the strains examined showed a clear preference to alter human glycol-conjugated BAs, although clear strain-dependent modifications were also evident. This study demonstrates that BA metabolism by food-borne non-pathogenic bacteria is beneficial to both microbe and man and it identifies an evolutionary-conserved characteristic, previously considered unique to gut residents, among food-associated non-pathogenic isolates.
Highlights
Bile acid (BA) signatures are altered in many disease states
Intestinal bacteria have a major role in bile salt metabolism[11,12] mainly through microbial bile salt hydrolase (BSH) enzymes that catalyse bile salts deconjugation by hydrolysis of the amide bond to release the glycine/taurine moiety from the steroid nucleus[9,13,14]
At tested concentrations below 1.8%, microbial viability was unaltered (Fig. 1a and SI Figure S1a) for the majority of strains, significant reductions in viability were recorded with type strains Lb. plantarum ATCC14917, CF1 and LT99 isolated from pickled cabbage, sourdough, raw-milk cheeses respectively
Summary
Bile acid (BA) signatures are altered in many disease states. BA metabolism is an important microbial function to assist gut colonization and persistence, as well as microbial survival during gastro intestinal (GI) transit and it is an important criteria for potential probiotic bacteria. Intestinal bacteria have a major role in bile salt metabolism[11,12] mainly through microbial bile salt hydrolase (BSH) enzymes that catalyse bile salts deconjugation by hydrolysis of the amide bond to release the glycine/taurine moiety from the steroid nucleus[9,13,14] This function is recognised as the crucial gateway reaction in BA biotransformation[9,14], www.nature.com/scientificreports regenerating primary free BA CA and CDCA, to facilitate microbial formation of secondary bile acid deoxycholic acid (DCA) from CA, lithocholic acid (LCA) and ursodeoxycholic acid (UDCA) from CDCA as well as a range of intermediates (reviewed by Long et al, 2017). Lactobacillus isolated from fermented milk show a preference for glyco conjugated bile acids, some overlap for tauro deconjugation ( TDCA) was detected for a number of strains[44]
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