Dual diaminopimelate biosynthesis pathways in Bacteroides fragilis and Clostridium thermocellum

► Locus tags Bf3481 and Cthe_0922 encode authentic forms of diaminopimelate dehydrogenase. ► Bf3481 defines a previously uncharacterized diaminopimelate dehydrogenase (Ddh). ► Ddh frequently occurs in the same genome as another diaminopimelate pathway. ► Ddh has a restricted phylogenomic distribution. ► Hypothesis: Ddh evolved recently as an ancillary diaminopimelate biosynthesis mechanism.