Novel aerobic 1,2-DCA degrading consortia from a contaminated aquifer for enhanced bioremediation purposes

Abstract

Anthropized environments are a source of unexplored microbial diversity and functions that can contribute to address emergent environmental threats in a sustainable way. 1,2-dichloroethane (1,2-DCA) is a toxic groundwater contaminant that can be aerobically and anaerobically biodegraded by specialized bacteria. The main aerobic catabolic pathways is hydrolytic dechlorination, mediated by the key enzyme DhlA. The aim of this study was to isolate and characterize novel degrading bacteria from an unexplored 1,2-DCA contaminated aquifer to exploit for enhanced bioremediation purposes. Enrichment cultures from groundwater samples were set up on mineral medium amended with 1,2-DCA as sole carbon source. The degradation abilities of enriched consortia were tested by Cl- release assay and Gas Chromatography-Mass Spectrometry. The consortia were PCR screened for the dhlA gene. The consortia composition was studied by Ion Torrent 16S rRNA gene sequencing. Whole genome sequencing was performed by Nanopore technology. Four stable 1,2-DCA-dechlorinating consortia with similar composition were obtained. All consortia consisted of known aerobic 1,2 DCA-degrading genus Ancylobacter and other genera with unclear role. The consortia degraded up to 1000 ppm 1,2-DCA in three days. The dhlA gene, identical to that of all other known aerobic 1,2-DCA degraders, and other genes involved in 1,2-DCA hydrolytic dechlorination were found and located on Ancylobacter chromosome in all consortia. The consortia can efficiently degrade 1,2-DCA to a concentration that was not tested yet for other known 1,2-DCA hydrolytic degraders. The dhlA gene, located on plasmids in other known 1,2-DCA degraders, was located on a chromosome and it was confirmed to be highly conserved and likely acquired by horizontal gene transfer. The consortia can be exploited in bioremediation as a nature-based solution relying on the sustainable use of biodiversity.