Project description:Few aerobic hyperthermophiles degrade polysaccharides. We describe the genome-enabled enrichment and isolation of an aerobic hyperthermophile, Fervidibacter sacchari, which was originally ascribed to candidate phylum Fervidibacteria. F. sacchari uses polysaccharides and monosaccharides as sole carbon sources from 65-87.5 °C, and its genome encodes 117 glycoside hydrolases (GHs) spanning 49 GH families, including 31 homologs of understudied GH109, GH177, and GH179 domains. Here, we analyzed the transcriptomes of F. sacchari cells grown on eight different sole carbon and energy sources (beta-glucan, chondroitin sulfate, corn stover, gellan gum, locust bean gum, starch, xanthan gum, and xyloglucan) to link glycoside hydrolase substrate to function, as well as identify potential regulatory mechanisms. These data will provide preliminary characterization of novel carbohydrate-active enzymes at high temperatures.
Project description:Fervidibacter sacchari PD1 cells were grown with beta-glucan, gellan gum, locust bean gum, starch, or xyloglucan as sole carbon/energy sources. Cellular and secreted proteins under each condition were analyzed with DIA proteomics.
Project description:The diets of industrialized countries reflect the increasing use of processed foods, often with the inclusion of novel food additives. Xanthan gum is a complex polysaccharide with unique rheological properties that have established its use as a widespread stabilizer and thickening agent. Xanthan gum’s chemical structure is distinct from the host and dietary polysaccharides that are more commonly expected to transit the gastrointestinal tract, and little is known about its direct interaction with the gut microbiota, which plays a central role in digestion of other dietary fiber polysaccharides. Here, we show that the ability to digest xanthan gum is surprisingly common in industrialized human gut microbiomes and appears contingent on a single uncultured bacterium in the family Ruminococcaceae. Our data reveal that this primary degrader cleaves the xanthan gum backbone before processing the released oligosaccharides using additional enzymes. Surprisingly, some individuals harbor a Bacteroides intestinalis that is incapable of consuming polymeric xanthan gum but grows on oligosaccharide products generated by the Ruminococcaceae. Feeding xanthan gum to germfree mice colonized with a human microbiota containing the uncultured Ruminococcaceae supports the idea that this additive can drive expansion of this primary degrader along with exogenously introduced Bacteroides intestinalis. Our work demonstrates the existence of a potential xanthan gum food chain involving at least two members of different phyla of gut bacteria and provides an initial framework to understand how widespread consumption of a recently introduced food additive influences human microbiomes.
