Isolation of novel bacteria within the Chloroflexi capable of reductive dechlorination of 1,2,3‐trichloropropane

Abstract

Two strictly anaerobic bacterial strains were isolated from contaminated groundwater at a Superfund site located near Baton Rouge, LA, USA. These strains represent the first isolates reported to reductively dehalogenate 1,2,3-trichloropropane. Allyl chloride (3-chloro-1-propene), which is chemically unstable, was produced from 1,2,3-trichloropropane, and it was hydrolysed abiotically to allyl alcohol and also reacted with the sulfide- and cysteine-reducing agents in the medium to form various allyl sulfides. Both isolates also dehalogenated a variety of other vicinally chlorinated alkanes (1,2-dichloropropane, 1,2-dichloroethane, 1,1,2-trichloroethane, 1,1,2,2- tetrachloroethane) via dichloroelimination reactions. A quantitative real-time PCR (qPCR) approach targeting 16S rRNA genes indicated that both strains couple reductive dechlorination to cell growth. Growth was not observed in the absence of hydrogen (H2) as an electron donor and a polychlorinated alkane as an electron acceptor. Alkanes containing only a single chlorine substituent (1-chloropropane, 2-chloropropane), chlorinated alkenes (tetrachlorothene, trichlorothene, cisdichloroethene, trans-dichloroethene, vinyl chloride) and chlorinated benzenes (1-chlorobenzene and 1,2- dichlorobenzene) were not dechlorinated. Phylogenetic analysis based on 16S rRNA gene sequence data showed these isolates to represent a new lineage within the Chloroflexi. Their closest previously cultured relatives are 'Dehalococcoides' strains, with 16S rRNA gene sequence similarities of only 90%.

Guided cobalamin biosynthesis supports Dehalococcoides mccartyi reductive dechlorination activity

“…Limited dechlorination activity of Dehalococcoides and related corrinoid-auxotroph, organohalide-respiring Chloroflexi (e.g. Dehalogenimonas [38,39], 'Dehalobium' [40]) is regarded as a major constraint to achieve detoxification at sites contaminated with chlorinated contaminants. Hence, elucidating the nutritional requirements and ecophysiologies of organohalide-respiring Chloroflexi in natural and contaminated environments will help develop predictive understanding and new strategies for stimulating in situ reductive dechlorination activity.…”

Sedimentological imprint on subseafloor microbial communities in Western Mediterranean Sea Quaternary sediments

“…These sequences were most closely related to clones obtained from marine subsurface sediments of Pacific Ocean margin (Inagaki et al, 2006), Gulf of Mexico (Nunoura et al, 2009) and from tidal flat sediments from the Wadden Sea (Wilms et al, 2006) (over 95 % sequence similarity). The closest cultured relative to our sequences was the bacterium Dehalogenimonas lykanthroporepellens strain BL-DC-9, with a sequence similarity of 89 %, a strain capable of reductively dehalogenating 1,2,3-trichloropropane (Yan et al, 2009). Details for sequence similarities of excised DGGE bands are available as Supplement information (Fig.…”

Dehalogenimonas lykanthroporepellens gen. nov., sp. nov., a reductively dehalogenating bacterium isolated from chlorinated solvent-contaminated groundwater

“…Two novel anaerobic bacterial strains that cluster within the phylum Chloroflexi, designated BL-DC-8 and BL- T , were recently demonstrated to be able to reductively dehalogenate a variety of polychlorinated alkanes (Yan et al, 2009). These represent the first strains isolated in pure culture to be able anaerobically to reductively dehalogenate 1,2,3-trichloropropane.…”

“…Scanning electron microscopy was performed as described by Yan et al (2009). For transmission electron microscopy, cells were collected and fixed in the same manner as for scanning electron microscopy.…”

“…Cells for analysis of cellular fatty acids were grown in anaerobic basal medium prepared as described by Yan et al (2009) except that the sodium sulfide solution was replaced with titanium citrate solution (Zehnder & Wuhrmann, 1976) as a reducing agent at a final concentration of 1.0 mM Ti(III) and 2.0 mM citrate. The medium was supplemented with 5 mM sodium acetate and 0.5 mM 1,1,2-trichloroethane, and provided with hydrogen gas (10 %, v/v) in the headspace.…”