Interspecies metabolite transfer in a co-culture of Dehalococcoides and Sulfurospirillum leads to rapid and complete tetrachloroethene dechlorination

Microbial communities involving dehalogenating bacteria assist in bioremediation of areas contaminated with chlorinated hydrocarbons. To understand molecular interactions between dehalogenating bacteria, we co-cultured two bacterial species dechlorinating chloroethenes: Sulfurospirillum multivorans , dechlorinating tetrachloroethene (PCE) to cis-1,2-dichloroethene (cDCE) and Dehalococcoides mccartyi strains BTF08 or 195, transforming PCE via cDCE to ethene. The interaction of these bacteria cultivated with lactate as electron donor and PCE as electron acceptor was investigated using growth studies, metabolite analysis, microscopy, isotope fractionation and proteomics. Co-cultures exhibited more than 3-fold higher PCE to ethene dechlorination rates than D. mccartyi pure cultures. S. multivorans provided hydrogen, acetate and the reductive dehalogenase cobamide cofactor to D. mccartyi . While D. mccartyi 195 dechlorinated cDCE in the presence of norpseudo-B12 produced by S. multivorans , cDCE dechlorination by D. mccartyi BTF08 depended on the supply of 5,6-dimethylbenzimidazole for producing functional cobamides. Co-cultures were characterized by the formation of aggregates and electron microscopy revealed an extracellular matrix enabling cell-to-cell contact. D. mccartyi showed an unusual barrel-like morphology, probably dependent on down-regulation of cell division gene expression, as observed in the co-culture proteome. Only the reductive dehalogenases PteA and VcrA were found in the proteomes of D. mccartyi BTF08 during dehalogenation of PCE to ethene.