Diversity of dehalorespiring bacteria and selective enrichment of aryl halides-dechlorinating consortium from sedimentary environment near an oil refinery

This study demonstrated the potential for reductive dechlorination of aryl halides in a sedimentary environment by naturally occurring bacteria. A laboratory sediment microcosm and highly enriched, stable dechlorinating cultures were established using hydrogen as electron donor and 2,3-dichlorophenol (2,3DCP), monochlorophenol (MCP) and dichlorobenzene (DCB) as electron acceptors. 16S rRNA gene sequencing of dominant DGGE bands assigned detected phylotypes in chlorophenols (CPs) amended sediment microcosms to the genera Anaerospora, Pseudomonas, Desulfitobacterium, Clostridium, Mycobacterium, and Peptoclostridium, beside uncultured marine Bacterioplankton, Halochromatium and Sedimentibacter. Chlorobenzene (CB) amended sediments showed the same community in addition to Bacillus sp. Major operational taxonomic units (OTUs) in CPs enrichment cultures were assigned to Anaerospora hongkongensis, Pseudomonas stutzeri, Pseudomonas pseudoalcaligenes, Clostridium sp., Desulfitobacterium dichioroeliminans, beside unidentified marine bacterioplankton. Enrichment on DCB resulted in predominance of the same populations in addition to Peptoclostridium sp. and Dehalococcoides mccartyi. Dechlorination in enrichment cultures was mainly assigned to Desulfitobacterium and Dehalococcoides, which are both known for their ability to couple dechlorination to growth in a halorespiration way. Enrichment cultures containing Desulfitobacterium showed ortho dechlorination activity of 2,3DCP to 2 chlorophenol (2CP) and 3 chlorophenol (3CP). These results provided compelling evidence that sedimentary environments in the vicinity of oil refineries do harbor dehalorespiring bacteria capable of reductive dechlorination of various aryl halides pollutants.