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 sub-cultured 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 octa-chlorinated 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.
Reductive dechlorination of polychlorinated biphenyls in marine sediments: evidence for the involvement of a Dehaloccoides-like bacterium in the process / G. Zanaroli; A. Balloi; A. Negroni; D. Daffonchio; F. Fava. - STAMPA. - (2009), pp. 224-224. (Intervento presentato al convegno 28th National Meeting tenutosi a Spoleto nel 11-13 Giugno 2009).
Reductive dechlorination of polychlorinated biphenyls in marine sediments: evidence for the involvement of a Dehaloccoides-like bacterium in the process
ZANAROLI, GIULIO;NEGRONI, ANDREA;FAVA, FABIO
2009
Abstract
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 sub-cultured 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 octa-chlorinated 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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
