Several studies detected PCB dechlorination activities in freshwater sediments under methanogenic conditions; however, bacteria of the phylum Chloroflexi have been recently identified as PCB dechlorinators in sediment-free cultures enriched from freshwater sediments in mineral medium. In this work we investigated the PCB dechlorinating microbial community of a contaminated marine sediment of the Venice lagoon (VL) enriched under laboratory geobiochemical conditions close to those occurring in situ. Native microflora was subcultured in slurry microcosms of VL sterile sediment suspended in sterile site water in the presence spiked PCBs (Aroclor 1254, 1 g/kg dry sediment). A marked dechlorination activity was detected towards penta- through octachlorinated biphenyls that were bioconverted by more than 70% into di-, tri- and tetra-chlorinated congeners after 30 weeks of incubation according to the dechlorination pattern H'. The addition of H2 and short chain organic acids increased sulfate-reducing and methanogenic activities, but finally resulted in a decrease of the dechlorination rate. When the same agents were applied together with vancomycin or ampicillin, higher dechlorination rates were observed, along with a remarkable inhibition of sulfate-reducing activity. Finally, the highest increase in the dechlorination rate was detected when vancomycin or ampicillin were singly added to the culture. DGGE analysis of 16S rRNA genes detected three bacteria belonging to Chloroflexi. However, only a Dehaloccoccoides-like microorganism, having high sequence similarity with the putative PCB dechlorinating bacterium m-1, was detected in all the actively PCB dechlorinating cultures while was absent in all the corresponding PCB-free controls. These findings suggest that a Dehalococcoides-like bacterium is involved in PCB dechlorination in the marine sediments of the Venice lagoon.
|Titolo:||Reductive dechlorination of polychlorinated biphenyls in marine sediments: evidence for the involvement of a dehaloccoides- like bacterium in the process|
DAFFONCHIO, DANIELE GIUSEPPE (Ultimo)
|Settore Scientifico Disciplinare:||Settore AGR/16 - Microbiologia Agraria|
|Data di pubblicazione:||set-2009|
|Digital Object Identifier (DOI):||10.1016/j.nbt.2009.06.375|
|Appare nelle tipologie:||01 - Articolo su periodico|