Degradation of riboflavin by alimentary bacteria of the ruminant and man: production of 7,8-dimethyl-10-carboxymethylisoalloxazine

Abstract

I . A new product of the bacterial degradation of riboflavin has been isolated from fermentations in vitro of mixtures of either rumen bacteria or caecal bacteria with excess of the vitamin.2 . This product has been identified as ~,8-dimethyl-ro-carboxymethylisoalloxazine and has also been shown to occur in the urine of ruminants and man.3. The bacterial formation of this compound is cornparedwith the bacterial formation of other isoalloxazines previously identified in similar incubation mixtures, and is discussed in relation to the factors influencing the mode of degradation of riboflavin.

Rare variants of the FMN riboswitch class in Clostridium difficile and other bacteria exhibit altered ligand specificity

“…genes downstream from the variant FMN RNAs remain unknown, and thus provide limited clues regarding the identity of the cognate ligand. Because many C. difficile strains already carry a gene for a putative riboflavin importer whose expression is controlled by an FMN riboswitch, we hypothesized that some bacteria might use variant FMN RNAs to control the expression of efflux pumps to alleviate the deleterious buildup of toxic FMN breakdown products (Fall and Petering 1956;West and Owen 1973). This would be analogous to the observed use of guanidine riboswitches for controlling the production of multidrug efflux pumps (Nelson et al 2017;Kermani et al 2018).…”

“…FMN and flavin adenine dinucleotide (FAD) are ordinarily used as redox cofactors for flavoenzymes involved in various aspects of cellular metabolism (Fischer and Bacher 2005). However, due to the high photoreactivity of these compounds, they can degrade into various toxic byproducts such as lumiflavin and lumichrome (Fall and Petering 1956;West and Owen 1973;Choe et al 2005). Some bacterial and archaeal cells protect themselves from these phototoxic products with riboflavin-binding proteins called dodecins that act to both store riboflavin and prevent its undesirable breakdown (Grininger et al 2006(Grininger et al , 2009.…”

Vitamin absorption in thein vivointestine of normal and infected (Hymenolepis diminuta: Cestoda) rats

“…Further, the inter-relationship between vitamins and intestinal bacterial flora is complex. Thiamine may be synthesized by the intestinal bacteria and absorbed by the intestine following coprophagy; similarly folic acid, which can also be absorbed directly (Klipstein and Samloff, 1966;Hoffbrand et al, 1971): riboflavin is degraded by the coliform bacteria (West and Owen, 1973).…”