Genetic analysis of a bile salt hydrolase inBifidobacterium animalissubsp.lactisKL612

Abstract

Aims: To clone, sequence and characterize a new bile salt hydrolase from a bile tolerant strain of Bifidobacterium animalis ssp. lactis KL612, and further analysis of the bsh promoter and an operon‐like structure containing the bsh gene in the genus Bifidobacterium. Methods and Results: A new type of bile salt hydrolase from a bile tolerant strain of Bifidobacterium was cloned, completely sequenced and characterized. The putative bsh promoter sequence was analysed by primer extension to determine the transcriptional start point by applying the genomic walking‐PCR, an operon‐like structure containing the bsh gene and two more open reading frames located within a complete set ranging from a promoter to a transcription terminator sequence is reported for the first time in the genus Bifidobacterium. The polycistronic bsh transcript was revealed by reverse transcriptase‐PCR (RT‐PCR) as well as by Northern hybridization. Conclusions: Most of bile tolerant strains of bifidobacteria showed a similar genetic organization around the bsh gene. This finding suggests that bile tolerance of those strains is possibly because of the bile salt hydrolase and some transporter proteins, which are functionally related to each other to respond efficiently to the stress from bile salts. Significance and Impact of the Study: Knowledge gained through BSH research would provide further insight into the survival of probiotics in the gastrointestinal tract and some physiological functions of this enzyme in relation to the host as well as the enzyme‐producing bacteria.

Probiotic Bile Salt Hydrolase: Current Developments and Perspectives

“…It has also been observed that pancreatin supported Bifidobacterium possesses natural tolerance to survive in the gastrointestinal tract and resist against the antimicrobial property of bile acids [34]. Bile salt tolerance of some microorganisms is possibly due to the presence of BSH and some transporter proteins, which are functionally related to each other to respond efficiently to the stress from bile salts [35]. Microbial traits, which would be expected to be appropriate for survival in the human gut, must be proficient to pathogens for bile resistance [36].…”

Discovering Novel Bile Protection Systems in Bifidobacterium breve UCC2003 through Functional Genomics

“…Bile exposure represents a key challenge for bacterial survival within the GIT, since bile salts are potent antimicrobial, detergent-like substances that, among other adverse effects, disrupt cell membranes, provoke oxidative damage and cause protein misfolding (2). Bile protection mechanisms employed by enteric bacteria remain poorly understood, although various bile-modifying enzymes (13) and bile transporters (32) have been described.…”

“…Moreover, transcription of betA was shown to be bile inducible (10). In addition, bifidobacterial bile-modifying enzymes have been described (9,13), although their precise contribution to bile tolerance is still obscure.…”

Other Organism‐Based Processes and Products

“…L. acidophilus is also reported to take up cholesterol during growth and this makes it unavailable for absorption into the blood stream, via several ways, namely, absorption of cholesterol to the cellular surface and incorporation of cholesterol into the phospholipid tails, upper phospholipids, and polar heads of the cellular membrane phospholipid bilayer (Lye, et al, 2010). The detailed genetic organization of BSHs from Bifidobacterium strains (Kim et al, 2004;Kim and Lee, 2008), bile salt biotransformations by human intestinal bacteria (Ridlon et al, 2006), and the presence of the bsh gene have also been reported. Most of the in vivo trials conducted thus far have focused heavily on verifying the hypocholesterolemic effects of probiotics, rather than the mechanisms involved.…”