Abstract
Probiotic bacteria exopolysaccharides (EPS) have been recognized as molecules that regulate immune development and have anti-inflammation and anticancer effects. Yet, these bioactivities are of interspecies diversity; thus, examining the gene clusters of EPS and biosynthesis pathways are essential for selecting the better application of specific EPS. In this study, we isolated a new Bifidobacterium strain, named B. breve lw01. A complete genome of B. breve lw01 was sequenced revealing a circular 2,313,172 bp chromosome. Furthermore, a deep excavation of genome sequence from different database based on the comparison-selected results was performed to explore the gene cluster responsible for EPS synthesis. We found that B. breve lw01 harbors a new EPS-encoding cluster with 14 predicted genes, which could be divided into three groups according to the biosynthesis pathway hypothesis. Using tertiary purification, high purity EPS were obtained. EPS is composed of rhamnose (Rha), arabinose (Ara), galactose (Gal), glucose (Glc), and mannose (Man) in a molar ratio of 0.35:0.44:1.38:0.67:1.65. With reference to its bioactivity, it showed to possess anticancer activity against Head and Neck Squamous Cell Carcinoma cell line by regulating cell cycle arrest and cell apoptosis promotion. To sum up, this study examined the biosynthesis and bioactivity of EPS using a new isolated B. breve strain, which could be used to clarify its further application in functional food or drug industry.
Highlights
MATERIALS AND METHODSMicrobial EPS are carbohydrate polymers surrounding the envelope of most bacteria
A total of 653 strains bacteria were isolated from the infant fecal samples
EPS obtained from probiotic bacteria Bifidobacterium have been gaining increasing attention, mainly due to their role in immune system and gut microbiota modulation
Summary
Microbial EPS are carbohydrate polymers surrounding the envelope of most bacteria. The bacterial EPS has initially gained lots of attention from researchers for its effect on biofilm or capsular polysaccharides formation that act as virulence factors in infectious diseases (Gonzalez-Escobedo et al, 2011; Yamanaka et al, 2011). For better application of specific bifido-EPS, gene clusters, chemical composition and its hypothetical biosynthesis pathways prediction need to be carefully examined. After genome sequencing and in silico analysis, a new EPS cluster and the hypothetical synthesis pathway were discovered. This study provided genetic information on EPS cluster from new isolated EPSproducing Bifidobacterium, connecting it with biosynthesis pathway and exploring its anti-tumor activities. Genomic DNA Isolation, Sequencing and Analysis of EPS Cluster in Bifidobacterium. The genomes and EPS cluster information available in the GenBank database were used for the comparative analysis among B. breve lw and several Bifidobacterium strains. Distilled water was applied to keep the pH of the ion exchange column neutral, eluted with 0.1, 0.2, 0.3, 0.4, and 0.5 M NaCl. The loading volume was 1 mL and the flow rate was 1 mL/min. A P-value < 0.05 was considered statistically significant
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