Project description:Bacteria of the genera Xylanibacter and Segatella are one of the most dominant groups in the rumen microbiota. They are characterized by the ability to utilize different hemicelluloses and pectin of plant cell-wall as well as plant energy storage polysaccharides. The degradation is possible with the use of cell envelope bound multiprotein apparatuses coded in polysaccharide utilization loci (PULs), which have been shown to be substrate specific. The knowledge of PUL presence in rumen Xylanibacter and Segatella based on bioinformatic analyses is already established and transcriptomic and genetic approaches confirmed predicted PULs for a limited number of substrates. In this study, we transcriptomically identified additional different PULs in Xylanibacter ruminicola KHP1 and Segatella bryantii TF1-3. We also identified substrate preferences and found that specific growth rate and extent of growth impacted the choice of substrates preferentially used for degradation. These preferred substrates were used by both strains simultaneously as judged by their PUL upregulation. Lastly, β-glucan and xyloglucan were used by these strains in the absence of bioinformatically and transcriptomically identifiable PUL systems.
Project description:Xylanibacter ruminicola is an abundant rumen bacterium that produces propionate in a cobalamin-dependent manner. However, the effect of cobalamin supplementation on the expression of propionate pathway enzymes has yet to be investigated. To assess this, comparative transcriptomics and proteomics was carried out on X. ruminicola KHP1 cultures grown in defined media in the presence and absence of cobalamin. Cobalamin supplementation did not affect expression of most propionate pathway proteins, with the only differentially abundant pathway enzyme being the cobalamin-dependent methylmalonyl-CoA mutase, which showed a minor upregulation in the presence of cobalamin. Our results demonstrate expression of the propionate pathway regardless of cobalamin availability, suggesting that cobalamin-dependent induction of propionate production by X. ruminicola is controlled post-translationally.
