9.B.327. The 1 or 2 component Reductive Dehalogenases (RDase) Family
Bioremediation of toxic organohalogens resulted in the identification of organohalide-respiring bacteria harbouring reductive dehalogenases (RDases). RDases consist of the catalytic subunit (RdhA, encoded by rdhA) that has a single N-terminal TMS, and a small putative membrane anchor (RdhB, encoded by rdhB with 3 TMSs) that locates the A subunit to the outside of the cytoplasmic membrane. An rdhA gene has been found in an uncultured δ-proteobacterial genome that was not accompanied by an rdhB gene, but it contained TMSs at its N-terminus. It is likely a hybrid of RdhA and RdhB, directly connected to the membrane with TMSs. Hybrid putative rdh genes are present in the genomes of pure cultures and uncultured members of Bacteriodetes and Delta-proteobacteria, but also in the genomes of the candidate divisions. The encoded hybrid putative RDases have the cytoplasmic or exoplasmic C-terminal localization and cluster phylogenetically separately from the existing RDase groups (Atashgahi 2019).