Updated project metadata. 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.