Dehalogenimonas formicexedens sp nov., a chlorinated alkane-respiring bacterium isolated from contaminated groundwater

Abstract

A strictly anaerobic, Gram-stain-negative, non-spore-forming bacterium designated NSZ-14(T), isolated from contaminated groundwater in Louisiana (USA), was characterized using a polyphasic approach. Strain NSZ-14(T) reductively dehalogenated a variety of polychlorinated aliphatic alkanes, producing ethene from 1,2-dichloroethane, propene from 1,2-dichloropropane, a mixture of cis- and trans-1,2-dichloroethene from 1,1,2,2-tetrachloroethane, vinyl chloride from 1,1,2-trichloroethane and allyl chloride (3-chloro-1-propene) from 1,2,3-trichloropropane. Formate or hydrogen could both serve as electron donors. Dechlorination occurred between pH 5.5 and 7.5 and over a temperature range of 20-37 degrees C. Major cellular fatty acids included C-18:1 omega 9c, C-14:0 and C-16:0. 16S rRNA gene sequence-based phylogenetic analysis indicated that the strain clusters within the class Dehalococcoidia of the phylum Chloroflexi, most closely related to but distinct from type strains of the species Dehalogenimonas alkenigignens (97.63% similarity) and Dehalogenimonas lykanthroporepellens (95.05 %). A complete genome sequence determined for strain NSZ-14(T) revealed a DNA G+C content of 53.96 mol%, which was corroborated by HPLC (54.1 +/- 0.2 mol% G+C). Genome-wide comparisons based on average nucleotide identity by orthology and estimated DNA-DNA hybridization values combined with phenotypic and chemotaxonomic traits and phylogenetic analysis indicate that strain NSZ-14(T) represents a novel species within the genus Dehalogenimonas, for which the name Dehalogenimonas formicexedens sp. nov. is proposed. The type strain is NSZ-14(T) (=HAMBI 3672(T)=JCM 19277(T)=VKM B-3058(T)). An emended description of Dehalogenimonas alkenigignens is also provided.