ABSTRACT:Dehalococcoides
(
Dhc
) has recently gained significant attention in microbial reductive dehalogenation due to its specialized ability to metabolize various halocarbons. While previous reports have documented
Dhc
-mediated dihaloelimination of 1,2-dichloroethane (1,2-DCA), 1,2-dichloropropane (1,2-DCP), and 1,2-dibromoethane, this study reveals an expansion of
Dhc
’s dihaloelimination substrate range. We successfully established PJ
DCA
and PJ
TCA
enrichment cultures from petroleum-contaminated soil, exhibiting dihaloelimination activity toward 1,1,2-trichloroethane (1,1,2-TCA), 1,2,3-trichloropropane (1,2,3-TCP), and 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA)—substrates previously only known to be transformed by other organohalide-respiring bacteria (OHRB). Amplicon sequencing revealed the predominance of
Dhc
as the primary OHRB within the PJ
DCA
and PJ
TCA
cultures, leading to the identification of two novel
Dhc
populations, designated as strains PJ
DCA
and PJ
TCA
, respectively. These strains showed robust growth yields of 4.1 ± 0.4 × 10
7
and 7.6 ± 0.4 × 10
7
cells per μmol Cl
−
released when using 1,2-DCA and 1,1,2-TCA as electron acceptors, respectively. Genomic analysis revealed a reductive dehalogenase (RDase) homologous to the characterized DcpA, an enzyme known for dihaloelimination activity. Proteomic studies confirmed the expression of this DcpA-like RDase during dihaloelimination of 1,2-DCA, 1,1,2-TCA, and 1,2-DCP. This work identifies
Dhc
strains that retain dihaloelimination activity toward classical substrates while expanding this capability to 1,1,2-TCA, 1,2,3-TCP, and 1,1,2,2-TeCA. The discovery of these versatile
Dhc
strains enhances our understanding of microbial dehalogenation potential across diverse geological settings and improves prospects for bioremediation of halogenated alkane contaminants.
IMPORTANCE:
This study identifies
Dehalococcoides
strains capable of dihaloeliminating diverse chlorinated alkanes (1,1,2-TCA, 1,2,3-TCP, 1,1,2,2-TeCA), expanding their bioremediation potential. These compounds are persistent groundwater contaminants with high toxicity. The discovery of
Dhc
populations (PJ
DCA
/PJ
TCA
) with robust growth yields (10
7
cells/μmol Cl
−
) and broad substrate range offers new solutions for detoxifying complex halogenated pollutant mixtures. The identification and proteomic confirmation of DcpA-like RDases (DheA) provide the genetic and functional basis for this expanded dihaloelimination capacity. These findings advance strategies for
in situ
remediation of industrial sites contaminated with C
2
-C
3
halocarbons, reducing ecological and human health risks.