About this Research Topic
Organohalides are organic molecules in which carbons are linked by covalent bonds to halogens, e.g. perchloroethene (PCE), hexachlorobenzene, polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). Those compounds were massively produced for agricultural or industrial use in the form of solvents, fungicides, dielectric fluids and flame retardants, and their improper handling resulted in worldwide contamination in subsurface environments, primarily in anoxic groundwater, soil and sediment. in situ bioremediation employing organohalide-respiring bacteria represents a sustainable, economic solution for the removal of organohalide pollutants, which has been widely used with great success for remediation of chlorinated ethenes.
The organohalide-respiring bacteria utilize several sets of functional enzymes to couple electron transfer from H2 and organic compounds (electron donors) to halogen removal from organohalides (electron acceptors). The key enzyme catalyzing the above-described process is a reductive dehalogenase (RDase). Although the microbial reductive dehalogenation has been discovered many years ago, advances in characterizing major organohalide-respiring bacteria and in analyzing crystal structures of reductive dehalogenases were made recently. Those progresses provide critical insights into microbial reductive dehalogenation, and bring us to a new stage to realize that there are many puzzles to solve in the mechanistic understanding and in the application of organohalide respiration in bioremediation. Therefore, we propose this Research Topic for Frontiers in Microbiology and solicit manuscripts related to the following aspects:
(1) Organohalide-respiring bacteria: in addition to known major players (e.g. Dehalococ-coides, Dehalogenemonas, Dehalobacter and Desulfitobacterium ) in microbial reductive dehalogenation, organohalide-respiring bacteria of new lineages continuously emerge and show distinct dehalogenation specificities. Information on organohalide-respiring bacteria of new lineages or with novel dechlorination capabilities is particularly welcome.
(2) RDase gene and electron transport chain: several genes encoding RDases for catalyzing halogen removal from chloroethenes, chlorophenols, chlorobenzenes and PCBs have been identified and characterized in Dehalococcoides, Dehalogenemonas, Dehalobacter and Desulfitobacterium, however, RDase genes for PBDEs and many other organohalides, as well as their environmental distribution, remain elusive. In addition, electron transport chains employed for organohalide respiration in Dehalococcoides and Desulfitobacterium are different, and many gaps exist in understanding the process and participating en-zymes.
(3) Dehalogenating microbial communities – their phylogeny & function: organohalide-respiring bacteria need to work closely with other microorganisms to achieve efficient halogen removal. An optimized dehalogenating microbial community holds the key for successful bioremediation of organohalide pollutants. Therefore, it is critical to under-stand the phylogenetic and functional diversity, as well as the intrinsic network of dehalogenating microbial communities.
(4) Organohalide bioremediation: given the complexity of successful bioremediation, it would be interesting to have information on new techniques or processes coupling orga-nohalide-respiring bacteria with the operation in bioreactors (or other bioremediation mimicing systems) to tackle problems in organohalide bioremediation.
This Research Topic welcomes original results related to above-described subtopics, as well as articles addressing the latest trends in mechanistic and application aspects of organohalide respiration.
Keywords: organohalide, dehalogenation, respiration, electron transport, Dehalococcoides
Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.