Polybrominated diphenyl ethers (PBDEs) can be reductively degraded by microorganisms under anaerobic conditions. However, little is known about the effect of electron donors on microbial communities involved in PBDEs degradation. Here we employed 454 Titanium pyrosequencing to examine the phylogenetic diversity, composition, structure and dynamics of microbial communities from microcosms under the conditions of different electron donor amendments. The community structures in each of the five alternate electron donor enrichments were significantly shifted in comparison with those of the control microcosm. Commonly existing OTUs between the treatment and control consortia increased from 5 to 17 and more than 50% of OTUs increased around 13.7 to 186 times at least in one of the microcosms after 90-days enrichment. Although the microbial communities at different taxonomic levels were significantly changed by different environmental variable groups in redundancy analysis, significant correlations were observed between the microbial communities and PBDE congener profiles. The lesser-brominated PBDE congeners, tri-BDE congener (BDE-32) and hexa-BDE, were identified as the key factors shaping the microbial community structures at OTU level. Some rare populations, including the known dechlorinating bacterium, Dehalobacter, showed significant positive-correlation with the amounts of PBDE congeners in the consortia. The same results were also observed on some unclassified bacteria. These results suggest that PBDEs-degrading microbial communities can be successfully enriched, and their structures and compositions can be manipulated through adjusting the environmental parameters.

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Polybrominated diphenyl ethers (PBDEs) are a class of widely used flame retardants that have been highly accumulated in sediments. It is reported that microorganisms play an important role in the reductive debromination of PBDEs in anaerobic sediments. However, little is known about the effects of electron donors on the microbial community structure and their debromination capacity in PBDE transformation. In this study, alternate carbon substrates were used as electron donors to enrich the PBDE-debrominating microbial consortia to evaluate the effects of electron donors on PBDE microbial debromination. Decabromodiphenyl ether (BDE-209) was found to be the dominant (more than 50%) PBDEs congener in all consortia, and the percentage of BDE-209 was deceased by 12% (methanol), 11% (ethanol), 8% (acetate), 9% (lactate), 5% (pyruvate), and 11% (no electron donors), while the relative abundances of most lesser-brominated PBDEs increased after 90-day incubation compared to the initial profile of PBDEs. Substantial shifts in the microbial community structure among different amendments were observed based on denaturing gradient gel electrophoresis results. Pseudomonas spp. were identified to be the predominant organisms and the abundances of Band R, which was associated with Pseudomonas sp. SCSWA09, was well correlated with the biodegradation rate of BDE-209. Finally, the microbial community structure was highly correlated with the concentration of deca-BDE, octa-BDE and total nitrogen. These results provide insights into in situ bioremediation of environments contaminated by PBDEs and our understanding of microbial ecology associated with PBDE-debromination.