Abstract
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.
Highlights
Polybrominated diphenyl ethers (PBDEs) have been integrated into common household and industrial appliances as flame retardants for more than three decades, and were estimated to be more than 67 million kilograms in annual global market demand [1]
Our results showed that diversities, compositions and structures of PBDE-degrading microbial communities shifted under different electron donor amendments, and such changes were closely related to the controlled environmental parameters
Almost all of the unclassified operational taxonomic units (OTUs) are the rare populations in the microcosms, except three unclassified Sphingobacteriales WCHB1–69 OTUs (5371, 5537 and 6617) and one unclassified Proteiniborus OTU (9046). Within these unclassified OTUs, only two OTUs (OTU5371 and OTU6703) were commonly present in all of the microcosms and around 48% of them were unique in one of the microcosms. These results clearly indicate that during the enrichment process, exogenous electron donor amended and PBDEs would act as two important selection factors, more functional bacteria involved in PBDEs bioremediation could be induced while some indigenous oligotrophic microorganisms could be inhibited, and the PBDE-debrominating bacteria appeared to be distinctly different from those previously reported dechlorinators
Summary
Polybrominated diphenyl ethers (PBDEs) have been integrated into common household and industrial appliances as flame retardants for more than three decades, and were estimated to be more than 67 million kilograms in annual global market demand [1]. As a result of the widespread use, PBDEs residues are found in a wide variety of environment, and their concentrations have increased exponentially [2,3]. Since increasing evidence shows that PBDEs are bioaccumulated and biomagnified, these compounds have been listed as the new Persistent Organic Pollutants (POPs), and their fate and transport in ecosystems have received worldwide attention. Similar to polychlorinated biphenyls (PCBs) in structure and characteristics, PBDEs are hydrophobic, semi-volatile, toxic, resistant to microbial degradation, and strong adsorption on sediments [4]. High concentrations of PBDEs, ranged from 51.3 to 365 ng/g in sediments have been detected in Guiyu of Guangdong Province [5], and the local environment is seriously polluted by these compounds due to open burning and uncontrolled dumpling processes. It is urgent to develop potential remediation technologies to remove, degrade, or immobilize PBDEs in heavy contaminated industrial sites
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