Molecular mechanisms underpinning host O-glycan metabolism by human gut symbionts

Van Bakel, Wouter (2023) Molecular mechanisms underpinning host O-glycan metabolism by human gut symbionts. Doctoral thesis, University of East Anglia.

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Ruminococcus gnavus is considered as a prevalent member of the ‘normal’ gut microbiota found in 90% of people and its ability to degrade mucin glycans is strain dependent. R. gnavus shows a disproportionate representation in several diseases. Previously, the capacity of R. gnavus ATCC 29149 glycoside hydrolases (GHs) to cleave fucose and sialic acid epitopes from mucin glycans has been demonstrated as an important colonisation factor. Here, we showed that R. gnavus ATCC 29149 RgGH98 releases blood group A trisaccharide (BgAtri) from mucin glycans, enabling R. gnavus E1 strain, which is not able to grow on mucin, to grow on RgGH98-treated mucin. Both R. gnavus ATCC 29149 and E1 strain could benefit from the released BgAtri and from access to the underlying mucin glycans. To analyse the full complement of GHs involved in mucin glycan degradation, we performed RNA sequencing (RNAseq) analysis of R. gnavus ATCC 29149 grown on mucin glycans. 12 GHs were chosen for further analysis, the activity of three fucosidases on mucin glycans was confirmed. In addition, two GH13 enzymes were analysed; RgGH13-1 and RgGH13-2 were found to be able to hydrolyse a1-4 and a1-6 links in pullulan, respectively. These enzymes may be implicated in glycogen metabolism. Using stable isotope probing (SIP), we investigated the capacity of gut microbes (from human faecal microbiota) to utilise Neu5Ac and 2,7-anhydro-Neu5Ac. Collinsella aerofaciens and Dorea longicatena were found to be highly induced in the presence of Neu5Ac while no large difference in the faecal microbiota was observed upon 2,7-anhydro-Neu5Ac supplementation. Together these data demonstrate that the mucin glycan foraging strategy of R. gnavus ATCC 29149 is based on the removal and utilisation of mucin glycan epitopes like fucose, Neu5Ac and BgA, and identified new enzymes and pathways that may be involved in R. gnavus adaptation to the mucus niche.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Chris White
Date Deposited: 19 Dec 2023 11:38
Last Modified: 19 Dec 2023 11:38


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