Abstract
BackgroundProbiotics have been used to regulate the gut microbiota and physiology in various contexts, but their precise mechanisms of action remain unclear.ResultsBy population genomic analysis of 418 Bifidobacterium longum strains, including 143 newly sequenced in this study, three geographically distinct gene pools/populations, BLAsia1, BLAsia2, and BLothers, were identified. Genes involved in cell wall biosynthesis, particularly peptidoglycan biosynthesis, varied considerably among the core genomes of the different populations, but accessory genes that contributed to the carbohydrate metabolism were significantly distinct. Although active transmission was observed inter-host, inter-country, inter-city, intra-community, and intra-family, a single B. longum clone seemed to reside within each individual. A significant negative association was observed between host age and relative abundance of B. longum, while there was a strong positive association between host age and strain genotype [e.g., single nucleotide polymorphisms in the arginine biosynthesis pathway]. Further animal experiments performed with the B. longum isolates via using a d-galactose-induced aging mouse model supported these associations, in which B. longum strains with different genotypes in arginine biosynthesis pathway showed divergent abilities on protecting against host aging possibly via their different abilities to modify the metabolism of gut microbes.ConclusionsThis is the first known example of research on the evolutionary history and transmission of this probiotic species. Our results propose a new mechanistic insight for promoting host longevity via the informed use of specific probiotics or molecules.C6zECjXNEMtWDBtQ97tKDmVideo abstract
Highlights
Probiotics have been used to regulate the gut microbiota and physiology in various contexts, but their precise mechanisms of action remain unclear
Effect of environmental factors on the human gut microbiota and bifidobacteria some studies have focused on the characteristics of the human gut microbiota at the genus, species, and even strain levels [65,66,67,68,69], the distribution of gut bacterial genera and Bifidobacterium species, and their relationships with host factors remain largely unknown for Chinese populations
Using a conceptual framework based on evolution and the pathogen transmission theory, we showed that B. longum had formed at least three geographically related populations and established the active transmission of B. longum strains across different types of hosts and according to geography and proximity
Summary
Probiotics have been used to regulate the gut microbiota and physiology in various contexts, but their precise mechanisms of action remain unclear. Intestinal commensal microbes make critical contributions to human health, and many elicit beneficial effects on the host. Bifidobacterium species are pioneer colonizers of the gut and have been associated with various health-promoting effects [1], the precise modes of action remain largely unknown. Longum), which belongs to the human core microbiome [8]. This species accounts for a higher proportion of Bifidobacterium species in the gut regardless of host age [1], is distributed broadly across the human lifespan [9], and is among a small subset of gut commensals that can colonize the gut for years [10]. B. longum is a potentially important organism with which to evaluate host– microbe coevolution in the gut
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