Abstract
Members of the genus Lactobacillus are commonly found at the gastrointestinal tract and other mucosal surfaces of humans. This genus includes various species with a great number of potentially probiotic bacteria. Other often-used probiotic species belong to Bifidobacterium, a genus almost exclusively associated with the gut. As probiotics must survive and be metabolically active at their target sites, namely host mucosal surfaces, consumption of host-produced glycans is a key factor for their survival and activity. The ability to metabolize glycans such as human milk oligosaccharides (HMOs), glycosaminoglycans and the glycan moieties of glycoproteins and glycolipids found at the mucosal surfaces grants a competitive advantage to lactobacilli and bifidobacteria. The analyses of the great number of sequenced genomes from these bacteria have revealed that many of them encode a wide assortment of genes involved in the metabolism and transport of carbohydrates, including several glycoside hydrolases required for metabolizing the carbohydrate moieties of mucins and HMOs. Here, the current knowledge on the genetic mechanisms, known catabolic pathways and biochemical properties of enzymes involved in the utilization of host-produced glycans by lactobacilli and bifidobacteria will be summarized.
Highlights
Microbes colonize every available body surface area where they establish symbiotic relationships among themselves and with the host
An understanding of the mechanisms utilized by these microorganisms to survive in the gut will help to understand their exact role that they play in health and disease development
Colonization of the gut by probiotic or commensal members of these genera relies on their saccharolytic capacity as revealed by the remarkable carbohydrate gene repertoires found in their genomes
Summary
Microbes colonize every available body surface area where they establish symbiotic relationships among themselves and with the host. As a result of this effort, solid evidence has been obtained demonstrating that gut microbiota exerts major effects on human physiology, from metabolism (Li et al, 2008) to behavior (Ezenwa et al, 2012) Alterations of this microbial community may have significant effects on the host health (Cho and Blaser, 2012; Claesson et al, 2012) and have been related to a number of diseases such as metabolic disorders (Sonnenburg and Backhed, 2016), inflammatory diseases (Blander et al, 2017), diabetes (Membrez et al, 2008; Vaarala et al, 2008) and coeliac disease (Collado et al, 2007), among others
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