Dehalogenimonas, a genus within the phylum Chloroflexota, belongs to the class Dehalococcoidia. Its members are strict anaerobic, obligate organohalide-respiring bacteria that derive energy from reductive dehalogenation reactions mediated by reductive dehalogenases. Dehalogenimonas identified to date can only use halogenated alkanes as electron acceptors and perform organohalide respiration through dichloroelimination reactions.
Focusing on "Microbial Ecology of Contaminated Environments," a research team from the Institute of Applied Ecology of the Chinese Academy of Sciences, in collaboration with researchers from the University of Tennessee, USA, has discovered and enriched a novel Dehalogenimonas strain capable of using various chlorinated alkenes, including vinyl chloride, for growth. This strain was isolated from grape pomace (GP) compost samples.
Using techniques such as metagenomics and metaproteomics, the researchers identified the gene responsible for vinyl chloride reductive dehalogenase, and named the strain 'Candidatus Dehalogenimonas etheniformans' strain GP. Previous studies had identified only certain strains of Dehalococcoides capable of respiratory metabolism for dechlorination of vinyl chloride, a known human carcinogen.
The researchers classified strain GP as a new species within the genus Dehalogenimonas, and the discovery of the strain GP expands the microbial resources available for the remediation of environments contaminated with organochlorine compounds.
To gain a comprehensive understanding of the evolutionary status, physiological and biochemical characteristics, and environmental remediation potential of strain GP, the researchers isolated strain GP under strict anaerobic culture conditions and conducted a comprehensive classification and identification study using whole-genome sequencing, comparative genomics analysis, phenotypic characterization, and physicochemical property analysis.
Compared to other known organohalide-respiring bacteria, genome of strain GP contains the highest number of homologous genes encoding reductive dehalogenases. Phylogenetic analysis based on the 16S rRNA gene and genomic sequences supports the conclusion that strain GP represents a new species within the genus Dehalogenimonas.
Physicochemical identification experiments revealed that strain GP shares certain similarities with reported strains of the genus Dehalogenimonas in terms of phenotypic characteristics, phospholipid fatty acid composition, and optimal growth conditions. However, it exhibits distinct differences in electron acceptor utilization. Strain GP efficiently dechlorinates various chlorinated ethenes, including vinyl chloride, and 1,2-dichloroethane via hydrogenolysis, resulting in the complete dechlorination to non-toxic ethene.
This study improves our understanding of the physiological and evolutionary characteristics of Dehalogenimonas members, providing theoretical support and strain resources for the bioremediation of halogenated hydrocarbon-contaminated sites.
The strain GP has been deposited at the China General Microbiological Culture Collection Center and the Biological Resource Center of the National Institute of Advanced Industrial Science and Technology of Japan.
The differential interference contrast microscopy, scanning electron microscopy, and cryo-electron tomography high-resolution images of strain GP. (Image by YANG Yi)
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