Project description:The degradation of glycosaminoglycans (GAGs) by intestinal bacteria is critical for their colonization in the human gut and the health of the host. Both Bacteroides and Firmicutes have been reported to degrade GAGs, while the enzymatic details of the latter remain largely unknown. In this study, we isolated a Firmicutes strain, Hungatella hathewayi N2-326, that can catabolize various GAGs. While H. hathewayi N2-326 was less efficient in utilizing chondroitin sulfate A (CSA) and dermatan sulfate (DS) than Bacteroides thetaiotaomicron, a characterized GAG degrader, it outperformed B. thetaiotaomicron in assimilating hyaluronic acid. Unlike B. thetaiotaomicron, H. hathewayi N2-326 could not utilize heparin. The chondroitin lyase activity of H. hathewayi N2-326 was found to be induced by CSA and displayed both cell-associated and extracellular distributions. We further identified and characterized the first chondroitin ABC lyase from Firmicutes. The recombinant H. hathewayi chondroitin ABC lyase was found to be a predominantly exolyase and exhibited higher specific activity than any other characterized chondroitin ABC lyase. Thus, the HH-chondroitin ABC lyase offers a viable commercial option for the production of chondroitin, dermatan, and hyaluronan oligosaccharides and potential medical applications.
Project description:Whole-transcriptome analysis was used to investigate the molecular interplay between three bacterial species that are members of the human gut microbiota. Bacteroides ovatus, Subdoligranulum variabile, and Hungatella hathewayi formed associations in cocultures fed barley β-glucan, a constituent of dietary fiber. B. ovatus depolymerized β-glucan and released, but did not utilize, 3-O-β-cellobiosyl-d-glucose (DP3) and 3-O-β-cellotriosyl-d-glucose (DP4). These oligosaccharides provided growth substrates for S. variabile and H. hathewayi with a preference for DP4 in the case of the latter species. There was increased transcription of a B. ovatus mixed-linkage-β-glucan utilization locus, as well as carbohydrate transporters in S. variabile and H. hathewayi when in batch coculture. Increased transcription of the β-glucan utilization locus did not occur in continuous culture. Evidence for interactions relating to provision of cobalamin, alterations to signaling, and modulation of the "stringent response" (an adaptation to nutrient deprivation) were detected. Overall, we established a bacterial consortium based on barley β-glucan in vitro, which can be used to investigate aspects of the functional blueprint of the human gut microbiota.IMPORTANCE The microbial community, mostly composed of bacterial species, residing in the human gut degrades and ferments polysaccharides derived from plants (dietary fiber) that would not otherwise be digested. In this way, the collective metabolic actions of community members extract additional energy from the human diet. While the variety of bacteria present in the microbial community is well known, the formation of bacterial consortia, and the consequent interactions that result in the digestion of dietary polysaccharides, has not been studied extensively. The importance of our work was the establishment, under laboratory conditions, of a consortium of gut bacteria that formed around a dietary constituent commonly present in cereals. This enabled the metabolic interplay between the bacterial species to be studied. This kind of knowledge is required to construct an interactive, metabolic blueprint of the microbial community that inhabits the human gut.
