Bifidobacterium longum LBUX23 Isolated from Feces of a Newborn; Potential Probiotic Properties and Genomic Characterization

Abstract

Bifidobacterium longum is considered a microorganism with probiotic potential, which has been extensively studied, but these probiotic effects are strain dependent. This work aims to characterize the probiotic potential, based on the biochemical and genomic functionality, of B. longum LBUX23, isolated from neonates’ feces. B. longum LBUX23 contains one circular genome of 2,287,838 bp with a G+C content of 60.05%, no plasmids, no CRISPR-Cas operon, possesses 56 tRNAs, 9 rRNAs, 1 tmRNA and 1776 coding sequences (CDSs). It has chromosomally encoded resistance genes to ampicillin and dicloxacillin, non-hemolytic activity, and moderate inhibition of Escherichia coli ATCC 25922 and to some emergent pathogen’s clinical strains. B. longum LBUX23 was able to utilize lactose, sucrose, fructooligosaccharides (FOS), and lactulose. The maximum peak of bacterial growth was observed in sucrose and FOS at 6 h; in lactose and lactulose, it was shown at 8 h. B. longum LBUX23 can survive in gastrointestinal conditions (pH 4 to 7). A decrease in survival (96.5 and 93.8%) was observed at pH 3 and 3.5 during 120 min. argC, argH, and dapA genes could be involved in this tolerance. B. longum LBUX23 can also survive under primary and secondary glyco- or tauro-conjugated bile salts, and a mixture of bile salts due to the high extracellular bile salt hydrolase (BSH) activity (67.3 %), in taurocholic acid followed by taurodeoxycholic acid (48.5%), glycocholic acid (47.1%), oxgall (44.3%), and glycodeoxycholic acid (29.7%) probably due to the presence of the cbh and gnlE genes which form an operon (start: 119573 and end: 123812). Low BSH activity was determined intracellularly (<7%), particularly in glycocholic acid; no intracellular activity was shown. B. longum LBUX23 showed antioxidant effects in DPPH radical, mainly in intact cells (27.4%). In the case of hydroxyl radical scavenging capacity, cell debris showed the highest reduction (72.5%). In the cell-free extract, superoxide anion radical scavenging capacity was higher (90.5%). The genome of B. longum LBUX23 contains PNPOx, AhpC, Bcp, trxA, and trxB genes, which could be involved in this activity. Regarding adherence, it showed adherence up to 5% to Caco-2 cells. B. longum LBUX23 showed in vitro potential probiotic properties, mainly in BSH activity and antioxidant capacity, which indicates that it could be a good candidate for antioxidant or anti-cholesterol tests using in vivo models.

Cholesterol lowering in diet-induced hypercholesterolemic mice using Lactobacillus bile salt hydrolases with different substrate specificities

“…Previous studies have reported that many Bifidobacterium and Lactobacillus strains are known to produce BSH. 31,32…”

Milk and Its Derivatives as Sources of Components and Microorganisms with Health-Promoting Properties: Probiotics and Bioactive Peptides

“…Survival in the low-pH environment of the gut is also important as a technological property, especially in the food sector, considering that yogurt and fermented milks are the most used carriers for probiotics administration. Despite the importance of efflux pumps and changes in the cell envelope [270][271][272], genomic analysis supported the identification of argC, argH, and dapA, as acid-tolerance-associated genes, which may play an essential role in high acid tolerance [273,274] in the probiotic Bifidobacterium longum NCIM 5672; (iii) antagonism against pathogens through production of antimicrobial compounds and short-chain lactic and fatty acids [275] with anti-inflammatory properties, gut barrier protection, and immunomodulation [276]. The bacteriocins are proteinaceous compounds that are able to damage the outer membrane of pathogenic bacteria, act as a protective barrier against biofilm development and have also been linked to probiotic immunomodulatory, anticancer, antioxidant, antibacterial, and cholesterol-lowering activities [277].…”