Versatility in Corrinoid Salvaging and Remodeling Pathways Supports Corrinoid-Dependent Metabolism in Dehalococcoides mccartyi

Abstract

ABSTRACTCorrinoids are cobalt-containing molecules that function as enzyme cofactors in a wide variety of organisms but are produced solely by a subset of prokaryotes. Specific corrinoids are identified by the structure of their axial ligands. The lower axial ligand of a corrinoid can be a benzimidazole, purine, or phenolic compound. Though it is known that many organisms obtain corrinoids from the environment, the variety of corrinoids that can serve as cofactors for any one organism is largely unstudied. Here, we examine the range of corrinoids that function as cofactors for corrinoid-dependent metabolism inDehalococcoides mccartyistrain 195.Dehalococcoidesbacteria play an important role in the bioremediation of chlorinated solvents in the environment because of their unique ability to convert the common groundwater contaminants perchloroethene and trichloroethene to the innocuous end product ethene. All isolatedD. mccartyistrains require exogenous corrinoids such as vitamin B12for growth. However, like many other corrinoid-dependent bacteria, none of the well-characterizedD. mccartyistrains has been shown to be capable of synthesizing corrinoidsde novo. In this study, we investigate the ability ofD. mccartyistrain 195 to use specific corrinoids, as well as its ability to modify imported corrinoids to a functional form. We show that strain 195 can use only specific corrinoids containing benzimidazole lower ligands but is capable of remodeling other corrinoids by lower ligand replacement when provided a functional benzimidazole base. This study of corrinoid utilization and modification byD. mccartyiprovides insight into the array of strategies that microorganisms employ in acquiring essential nutrients from the environment.