Fig. 1

Schematic representing possible C. elegans and bacterial-dependent routes of folic acid supplementation. C. elegans depends on E. coli for folate. E. coli synthesizes reduced tetrahydrofolates de novo via the PABA pathway. The synthetic folate supplement, folic acid, is oxidised and must be enzymatically reduced into a tetrahydrofolate before it is bioavailable. E. coli cannot take up intact folic acid, but it can take up the breakdown product, PABA-glu. The inner membrane transporter AbgT transports PABA-glu, where it is cleaved intracellularly by a heterodimeric complex to generate PABA. Free PABA is then used to generate tetrahydrofolates. It is not clear whether this bacterial pathway is significant in the supplementation of an animal by folic acid