Disrupting either one uptake hydrogenase or the six-subunits energy-conserving hydrogenase selleck in Desulfitobacterium dehalogenans led to loss of the ability to grow using lactate or formate as electron donor and 3-chloro-4-hydroxyphenylacetate as electron acceptor, indicating that hydrogenases may play an important role in the electron transport chain to RD catalytic subunits, even when hydrogen is not used as the initial electron donor [55]. The role of the six-subunit hydrogenase complexes are still poorly understood. It has been speculated that they play a role in generating low potential electrons for OHR by reverse electron flow. However, this was considered as unlikely in one study where Dehalococcoides mccartyi strain 195 was cultivated in the presence of varying concentrations of hydrogen [56].

The exact role of the different hydrogenases in Dehalobacter restrictus strain PER-K23 still needs further studies. The genome also encodes an intact Wood-Ljungdahl pathway (Dehre_0130-0155 and 2348-2351). The presence of a whole or partial Wood-Ljungdahl pathway has been observed in other OHRB. The closely related Desulfitobacterium hafniense strains Y51 and DCB-2 both contain genes predicted to encode a full Wood-Ljungdahl pathway, and strain DCB-2 has been shown to fix CO2 [43,44]. The more distantly related Dehalococcoides mccartyi strains have been shown to contain partial Wood-Ljungdahl pathways, but its exact role in the metabolism of these organisms remains unclear [57,58]. The genome of D.

restrictus contains 72 genes annotated as encoding transposases or inactive derivatives thereof, whereas it only contains few phage-associated genes despite the lack of a CRISPR phage immunity system. Cells of Dehalobacter restrictus strain PER-K23 are motile [1]. The genome contains genes for synthesis of flagella and several genes predicted to be involved in chemotaxis. The role of chemotaxis in OHRB is currently understudied. Chemotactic behavior towards metals has been described for Geobacter, some members of this genus have been shown to be OHRB. Chemotactic behavior towards organohalides has, however, not been described for Geobacter spp [59-61]. Conclusion The presence of an unexpectedly large number of putative RDH encoding genes suggests a far larger potential for use in bioremediation than previously anticipated, especially if Dehalobacter restrictus strain PER-K23 is attracted by organohalides in a chemotactic manner. The complete genome sequence of Dehalobacter restrictus strain PER-K23, the type strain of the genus Dehalobacter, represents a significant leap Dacomitinib towards understanding the physiology, ecology and evolution of this specialized organohalide respiring group of bacteria.