Bar-coded pyrosequencing reveals the responses of PBDE-degrading microbial communities to electron donor amendments

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.     

Microbial Electricity Generation Enhances Decabromodiphenyl Ether (BDE-209) Degradation

Due to environmental persistence and biotoxicity of polybrominated diphenyl ethers (PBDEs), it is urgent to develop potential technologies to remediate PBDEs. Introducing electrodes for microbial electricity generation to stimulate the anaerobic degradation of organic pollutants is highly promising for bioremediation. However, it is still not clear whether the degradation of PBDEs could be promoted by this strategy. In this study, we hypothesized that the degradation of PBDEs (e.g., BDE-209) would be enhanced under microbial electricity generation condition. The functional compositions and structures of microbial communities in closed-circuit microbial fuel cell (c-MFC) and open-circuit microbial fuel cell (o-MFC) systems for BDE-209 degradation were detected by a comprehensive functional gene array, GeoChip 4.0, and linked with PBDE degradations. The results indicated that distinctly different microbial community structures were formed between c-MFCs and o-MFCs, and that lower concentrations of BDE-209 and the resulting lower brominated PBDE products were detected in c-MFCs after 70-day performance. The diversity and abundance of a variety of functional genes in c-MFCs were significantly higher than those in o-MFCs. Most genes involved in chlorinated solvent reductive dechlorination, hydroxylation, methoxylation and aromatic hydrocarbon degradation were highly enriched in c-MFCs and significantly positively correlated with the removal of PBDEs. Various other microbial functional genes for carbon, nitrogen, phosphorus and sulfur cycling, as well as energy transformation process, were also significantly increased in c-MFCs. Together, these results suggest that PBDE degradation could be enhanced by introducing the electrodes for microbial electricity generation and by specifically stimulating microbial functional genes.     

Isolation of Acetobacterium sp. Strain AG,Which Reductively Debrominates Octa- and Pentabrominated Diphenyl Ether Technical Mixtures

Polybrominated diphenyl ethers (PBDEs) are a class of environmental pollutants that have been classified as persistent organic pollutants since 2009. In this study, a sediment-free enrichment culture (culture G) was found to reductively debrominate octa- and penta-BDE technical mixtures to less-brominated congeners (tetra-, tri-, and di-BDEs) via a para-dominant debromination pattern for the former and a strict para debromination pattern for the latter. Culture G could debrominate 96% of 280 nM PBDEs in an octa-BDE mixture to primarily tetra-BDEs in 21 weeks. Continuous transferring of culture G with octa-/penta-BDEs dissolved in n-nonane or trichloroethene (TCE) yielded two strains (Acetobacterium sp. strain AG and Dehalococcoides sp. strain DG) that retained debromination capabilities. In the presence of lactate but without TCE, strain AG could cometabolically debrominate 75% of 275 nM PBDEs in a penta-BDE mixture in 33 days. Strain AG shows 99% identity to its closest relative, Acetobacterium malicum. In contrast to strain AG, strain DG debrominated PBDEs only in the presence of TCE. In addition, 18 out of 19 unknown PBDE debromination products were successfully identified from octa- and penta-BDE mixtures and revealed, for the first time, a comprehensive microbial PBDE debromination pathway. As an acetogenic autotroph that rapidly debrominates octa- and penta-BDE technical mixtures, Acetobacterium sp. strain AG adds to the still-limited understanding of PBDE debromination by microorganisms.     

Characterization of an enrichment culture debrominating tetrabromobisphenol A and optimization of its activity under anaerobic conditions

Aim: To study the effects of incubation conditions on the microbial community structure and activity of a TBBPA‐debrominating enrichment culture composed of bacterial and archaeal species. Methods and Results: The effects of the methanogen inhibitor 2‐bromoethanesulfonate (BES), of the antibiotic ampicillin, of substrate (tetrabromobisphenol A, TBBPA) omission and availability of different electron donors on microbial community structure and activity were examined under anaerobic conditions. Debromination of TBBPA was blocked in the presence of ampicillin, while long‐term incubation with BES resulted in delayed debromination activity. The results suggest that the bacterial species responsible for the debromination of TBBPA, while archaeal species involved in electron donor metabolism. The enrichment culture lost its debromination activity after cultivation for 9 months without TBBPA, concomitantly with the disappearance of two DNA bands in a denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene fragments corresponding to Pelobacter carbinolicus and Sphaerochaeta sp. TQ1 that were present in the original culture. When butyrate was used as an electron donor, TBBPA debromination activity was attenuated. When acetate was used as the electron donor, no debromination was observed and in addition, there was a decrease in the abundance of the mcrA gene. Conclusions: The results indicate that to maintain a high rate of TBBPA debromination activity, it is essential to preserve the microbial community structure (bacterial and archaeal members) of this culture and supply an electron donor that produces high amounts of hydrogen when fermented. Significance and Impact of the Study: The study provides important information for the management of cultures to be used in bioremediation of TBBPA contaminated sites.     

Loss of the ssrA genome island led to partial debromination in the PBDE respiring Dehalococcoides mccartyi strain GY50

Polybrominated diphenyl ethers (PBDEs), chemicals commonly used as flame‐retardants in consumer products, are emerging persistent organic pollutants that are ubiquitous in the environment. In this study, we report a PBDE‐respiring isolate – Dehalococcoides mccartyi strain GY50, which debrominates the most toxic tetra‐ and penta‐BDE congeners (～1.4 µM) to diphenyl ether within 12 days with hydrogen as the electron donor. The complete genome sequence revealed 26 reductive dehalogenase homologous genes (rdhAs), among which three genes (pbrA1, pbrA2 and pbrA3) were highly expressed during PBDE debromination. After 10 transfers of GY50 with trichloroethene or 2,4,6‐trichlorophenol as the electron acceptor instead of PBDEs, the ssrA‐specific genome island (ssrA‐GI) containing pbrA1 and pbrA2 was deleted from the genome of strain GY50, leading to two variants (strain GY52 with trichloroethene, strain GY55 with 2,4,6‐trichlorophenol) with identically impaired debromination capabilities (debromination of penta‐/tetra‐BDEs ceased at di‐BDE 15). Through analysis of Illumina paired‐end sequencing data, we identified read pairs that probably came from variants that contain ssrA‐GI deletions, indicating their possible presence in the original strain GY50 culture. The two variant strains provide real‐time examples on rapid evolution of organohalide‐respiring organisms. As PBDE‐respiring organisms, GY50‐like strains may serve as key players in detoxifying PBDEs in contaminated environments.     

Identification and biodegradation efficiency of a newly isolated 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) aerobic degrading bacterial strain

Polybrominated diphenyl ethers (PBDEs) are bioaccumulative, toxic and persistent, globally distributed organic chemicals in environment. However, very little is known for their aerobic biodegradation. In this research, 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) was selected as a model congener of PBDEs to study its aerobic biodegradation. A new BDE-47 degrading strain BFR01 identified as Pseudomonas stutzeri was isolated from polluted soil in a former brominated flame retardant production corporation. Stain BFR01 could utilize BDE-47 as a sole source of carbon and energy, and transformed 97.94% of BDE-47 in two weeks; the biodegradation of BDE-47 fitted well with the first-order kinetics, with the first-order kinetics constant of 0.32 d⁻¹. The biodegradation efficiency of stain BFR01 was higher than other reported PBDEs aerobic degrading bacteria. The biodegradation efficiency achieved maximum at pH 7.0 and 40 °C. The presence of additional carbon sources could enhance the biodegradation efficiency of BDE-47 by 1–6%. Furthermore, no lower brominated diphenyl ethers or biphenyl were detected, suggesting that the pathway of BDE-47 biodegradation by strain BFR01 might not be debromination with lower brominated diphenyl ethers as products. This is the first report of aerobic degradation of BDE-47 by P. stutzeri.     

Reductive Debromination of Polybrominated Diphenyl Ethers by Anaerobic Bacteria from Soils and Sediments

Polybrominated diphenyl ethers (PBDEs) have attracted attention recently due to their proven adverse effects on animals and their increasing concentrations in various environmental media and biota. To gain insight into the fate of PBDEs, microcosms established with soils and sediments from 28 locations were investigated to determine their debromination potential with an octa-brominated diphenyl ether (octa-BDE) mixture consisting of hexa- to nona-BDEs. Debromination occurred in microcosms containing samples from 20 of the 28 locations when they were spiked with octa-BDE dissolved in the solvent trichloroethene (TCE), which is a potential cosubstrate for stimulating PBDE debromination, and in microcosms containing samples from 11 of the 28 locations when they were spiked with octa-BDE dissolved in nonane. Debromination products ranging from hexa- to mono-BDEs were generated within 2 months. Notably, the toxic tetra-BDEs accounted for 50% of the total product. In sediment-free culture C-N-7* amended with the octa-BDE mixture and nonane (containing 45 nM nona-BDE, 181 nM octa-BDEs, 294 nM hepta-BDE, and 19 nM hexa-BDE) there was extensive debromination of the parent compounds, which produced hexa-BDE (56 nM), penta-BDEs (124 nM), and tetra-BDEs (150 nM) within 42 days, possibly by a metabolic process. A 16S rRNA gene-based analysis revealed that Dehalococcoides species were present in 11 of 14 active microcosms. However, unknown debrominating species in some of the microcosms debrominated the octa-BDE mixture in the absence of other added halogenated electron acceptors (such as TCE). These findings provide information that is useful for assessing microbial reductive debromination of higher brominated PBDEs to less-brominated congeners, a possible source of the more toxic congeners (e.g., penta- and tetra-BDEs) detected in the environment.Since they were first developed in the 1960s, polybrominated diphenyl ethers (PBDEs) have been used as flame retardant additives in an array of common household and industrial appliances. As a result of their widespread use, PBDEs have become ubiquitous environmental contaminants, and increasing levels have been detected in the air, soil, and water (5, 12). In a recent study, Leung et al. reported the highest PBDE concentrations in soil samples (2.7 to ∼4.3 ppb) and combusted residues (33.0 to ∼97.4 ppb) that were collected in Guiyu, Guangdong Province, China (18). More worrisome is the fact that increasing concentrations of PBDEs have also been detected in marine mammals, birds, fishes, and human tissues (3, 14, 20, 30), and 63 ppm of PBDEs in bird eggs is the highest level ever found in biota (23). The PBDE concentrations in both environmental samples and biota have been increasing exponentially, with a doubling time of 4 to 6 years (5, 12). Although the PBDEs comprise 209 different congeners designated 1 to 209, the PBDE congeners most often detected in biota (e.g., human tissues) include tetra-brominated diphenyl ether (tetra-BDE) (congener 47), penta-BDEs (congeners 99 and 100), and hexa-BDEs (congeners 153 and 154), which may have originated directly from a commercially available penta-BDE technical mixture or indirectly via breakdown of an octa- or deca-BDE technical mixture (10, 12). PBDEs began to receive worldwide scientific and public attention when a temporal study performed from 1972 to 1997 revealed increasing concentrations of PBDEs in Swedish human breast milk (19). Toxicological studies of rodents using a commercial penta-BDE mixture (including tetra-, penta- and hexa-BDEs) and congeners in a commercial octa-BDE mixture (such as hepta-BDE [congener 183] and octa-BDE [congener 203]) revealed developmental neurotoxicity, reproductive toxicity, liver toxicity, and disruption of thyroid hormone levels (24, 26, 29).To date, studies of PBDEs have focused mainly on detection of these compounds in the environment and their potential adverse health effects; only a few studies have reported microbial debromination of PBDEs (7, 10, 22, 25). Recently, He et al. demonstrated debromination of a technical octa-BDE mixture by pure isolates of Dehalococcoides species, which generated hepta- to di-BDEs after 6 months of incubation (10). Additionally, microbes belonging to the genera Dehalobacter and Desulfitobacterium were also found to be able to debrominate individual PBDE congeners present in commercial octa-BDE mixtures (10, 22). However, the debromination of PBDEs in both studies required the presence of a primary electron acceptor (e.g., chloroethenes or chlorophenols); in other words, debromination occurred cometabolically.In addition to debromination of PBDEs by pure cultures, a previous study demonstrated that in anaerobic sludge 5% of added deca-BDE (congener 209) was debrominated to nona- and octa-BDEs (total amount of product, 0.5 nmol) after 238 days of incubation (7). Moreover, another study showed that deca-BDE was debrominated to products ranging from nona-BDEs to hexa-BDEs in 3.5 years with anaerobic sediments as the inocula (25). These findings suggest that microbial reductive debromination of highly brominated congeners, such as deca-, nona-, octa-, and hepta-BDEs, may contribute to formation of less-brominated PBDEs in the environment, which are potentially more toxic (e.g., tetra- and penta-BDEs). Additionally, debromination of less-brominated PBDE congeners, such as di-BDE, to mono-BDE and diphenyl ether was demonstrated in a fixed-film plug flow biological reactor (21). Besides microbial debromination, highly brominated PBDEs were also found to be transformed to lower congeners via photodegradation or in vivo metabolism in aquatic and terrestrial animals (1, 16).This study was initiated to obtain information about the distribution of microorganisms capable of debrominating highly brominated PBDE congeners to more toxic daughter products or the final product diphenyl ether by assessing microcosm samples collected from various locations. Debromination of an octa-BDE mixture was evaluated in the presence of the potential energy-generating cosubstrate trichloroethene (TCE) (PBDEs dissolved in TCE) or in the presence of the relatively inert solvent nonane (PBDEs dissolved in nonane). The latter experiment provided, for the first time, information about the possible microbes living on the energy generated from the debromination of an octa-BDE mixture in the absence of any cosubstrate, such as TCE or another primer compound. Initial insights into the key debrominating microbes were obtained by using genus-specific 16S rRNA gene-based techniques.     

Elevated nitrate enriches microbial functional genes for potential bioremediation of complexly contaminated sediments

Nitrate is an important nutrient and electron acceptor for microorganisms, having a key role in nitrogen (N) cycling and electron transfer in anoxic sediments. High-nitrate inputs into sediments could have a significant effect on N cycling and its associated microbial processes. However, few studies have been focused on the effect of nitrate addition on the functional diversity, composition, structure and dynamics of sediment microbial communities in contaminated aquatic ecosystems with persistent organic pollutants (POPs). Here we analyzed sediment microbial communities from a field-scale in situ bioremediation site, a creek in Pearl River Delta containing a variety of contaminants including polybrominated diphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs), before and after nitrate injection using a comprehensive functional gene array (GeoChip 4.0). Our results showed that the sediment microbial community functional composition and structure were markedly altered, and that functional genes involved in N-, carbon (C)-, sulfur (S)-and phosphorus (P)- cycling processes were highly enriched after nitrate injection, especially those microorganisms with diverse metabolic capabilities, leading to potential in situ bioremediation of the contaminated sediment, such as PBDE and PAH reduction/degradation. This study provides new insights into our understanding of sediment microbial community responses to nitrate addition, suggesting that indigenous microorganisms could be successfully stimulated for in situ bioremediation of POPs in contaminated sediments with nitrate addition.     

Biomonitoring of polybrominated diphenyl ether (PBDE) pollution: a field study

Polybrominated diphenyl ethers (PBDEs) and cytochrome P450 enzyme activities were investigated in European eels (Anguilla anguilla) collected from seven sites in a coastal lagoon in the north-western Mediterranean Sea, Orbetello lagoon (Italy). Twelve PBDE congeners were measured in muscle and two CYP1A enzyme activities, 7-ethoxyresorufin-O-deethylase (EROD) and benzo(a)pyrene monooxygenase (BP(a)PMO), were investigated in liver microsomal fraction in order to obtain insights into the health of the lagoon environment. PBDE muscle levels were low and the most abundant congeners were 2,2',4,4'-tetrabromodiphenylether (BDE-47), 2,2',4,4',5,5'-hexaBDE (BDE-153) and 2,2',4,5'-tetraBDE (BDE-49). EROD and B(a)PMO activities were also low and no differences were observed between eels from different sites. Multivariate analysis (PCA) did not indicate correlations between PBDEs and either P450 activities.     

Microbial community shift with decabromodiphenyl ether (BDE 209) in sediments of the Pearl River estuary, China

To compare the effect of decabromodiphenyl ether (BDE 209) on microbial community from the Pearl River estuary, the microbial community at three in situ sites and the responses of microbial community to BDE-209 stressor were investigated. Denaturing gradient gel electrophoresis analysis of 16S rRNA gene showed that microbial community at site A2 has less diversity than sites A1 and A3. Physicochemical parameters (NH₄-N, salinity and SiO₃-Si) could significantly impact the microbial community composition in this estuary. In laboratory-incubated experiments, results indicated high concentration of BDE 209 (100 mg/kg) could increase the microbial diversity at sites A1 and A2, whereas reduced the microbial diversity at site A3. The unweighted pair group method with arithmetic means cluster analysis and principal component analysis demonstrated that the community structure changes at sites A1 and A2 were driven by the BDE 209 concentration, whereas at site A3 they depended on the incubation time. Thirty-five days after the addition of 100 mg/kg BDE 209, Firmicutes were found to be the dominant bacteria at sites A1 and A2. These data suggest the BDE 209 may have different effects on the microbial community in the Pearl River estuary.     

Pollutant Dehalogenation Capability May Depend on the Trophic Evolutionary History of the Organism: PBDEs in Freshwater Food Webs

Organohalogen compounds are some of the most notorious persistent pollutants disturbing the Earth biosphere. Although human-made, these chemicals are not completely alien to living systems. A large number of natural organohalogens, part of the secondary metabolism, are involved in chemical trophic interactions. Surprisingly, the relationship between organisms' trophic position and synthetic organohalogen biotransformation capability has not been investigated. We studied the case for polybromodiphenyl ethers (PBDE), a group of flame-retardants of widespread use in the recent years, in aquatic food webs from remote mountain lakes. These relatively simple ecosystems only receive pollution by atmospheric transport. A large predominance of the PBDE congener currently in use in Europe, BDE-209, largely dominated the PBDE composition of the basal resources of the food web. In contrast, primary consumers (herbivores and detritivores) showed a low proportion of BDE-209, and dominance of several less brominated congeners (e.g. BDE-100, BDE47). Secondary consumers (predators) showed large biomagnification of BDE-209 compare to other congeners. Finally, top predator fish characterized by low total PBDE concentrations. Examination of the bromine stable isotopic composition indicates that primary consumers showed higher PBDE biotransformation capability than secondary consumers. We suggest that the evolutionary response of primary consumers to feeding deterrents would have pre-adapted them for PBDE biotransformation. The observed few exceptions, some insect taxa, can be interpreted in the light of the trophic history of the evolutionary lineage of the organisms. Bromine isotopic composition in fish indicates that low PBDE values are due to not only biotransformation but also to some other process likely related to transport. Our finding illustrates that organohalogen compounds may strongly disturb ecosystems even at low concentrations, since the species lacking or having scarce biotransformation capability may be selectively more exposed to these halogenated hydrophobic semi-volatile organic pollutants due to their high bioaccumulation potential.     

Pleurozium schreberi as an ecological indicator of polybrominated diphenyl ethers (PBDEs) in a heavily industrialized urban area

Polybrominated diphenyl ethers (PBDEs) are toxic contaminants with a persistent character and adverse effects on humans and wildlife. Therefore, the deposition of these chemicals in vegetation must be carefully controlled. Our objective was to determine PBDE concentrations (BDEs 28, 47, 66, 85, 99, 100, 153, 154, 183 and 209) in Pleurozium schreberi collected in a heavily industrialized urban agglomeration. High PBDE concentrations in the moss confirm the presence of active sources of atmospheric pollution in an area tested. The distribution of these xenobiotics was related to the vegetation cover being lower in sites surrounded by forests which indicates that PBDEs may have a tendency to be trapped from the air by tree leaves and needles. Congener profiles in P. schreberi were dominated by BDE 209 which was for 79% (in case of the coke smelter) to 95% (in case of the chemical plant) part of the total PBDE burden in this moss. The principal component and classification analysis classifying the concentration of PBDEs in P. schreberi allowed us to distinguish the pattern of these compounds characteristic for the origin of pollution. P. schreberi may be used as a bioindicator for PBDEs in areas contaminated with these chemicals.     

Bacterial communities and nitrogen transformation genes in streambank legacy sediments and implications for biogeochemical processing

Streambank legacy sediments may be important sources of sediment and nutrients from Mid-Atlantic watersheds. However, little is known about the nutrient processing roles of microorganisms that inhabit legacy sediments, let alone their composition, diversity, and distributions. In this study, we sampled 15 streambanks at multiple depths throughout four watersheds in the Mid-Atlantic Region of the USA. High throughput sequencing of 16S ribosomal RNA genes indicated that streambank microbial community composition varied within site depth and across contemporary land uses. Collectively, the most abundant microbial taxa in legacy sediments included Acidobacteria (25–45%), Proteobacteria (15–40%), Nitrospirae (2–10%), Chloroflexi (1–5%), and Actinobacteria (1–10%). Bacterial community composition was distinct between agriculture and urban sites as well as suburban and urban sites. There was significant variation in community composition between the top (1–25%), upper-middle (26–50%), and bottom layers (76–100%) of sediments, while the relative abundances differed between layers for only Acidobacteria and Proteobacteria. Several streambank chemistry variables (metals, %TC, and %TN) had weak positive correlations with community composition. Compared to ammonia-oxidizing bacteria, nitrifying archaea were more predominant. This study provides the first insights into detailed microbial composition of legacy sediments and identifies environmental drivers for community structure and nitrogen processing. Future studies should consider exploring the role of this unique microbial environment for nutrient processing and leaching from legacy sediments and its implications for watershed water quality.

     

Induction of Adipocyte Differentiation by Polybrominated Diphenyl Ethers (PBDEs) in 3T3-L1 Cells

Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardants that were extensively used in commercial products. PBDEs are ubiquitous environmental contaminants that are both lipophilic and bioaccumulative. Effects of PBDEs on adipogenesis were studied in the 3T3-L1 preadipocyte cell model in the presence and absence of a known adipogenic agent, dexamethasone (DEX). A PBDE mixture designed to mimic body burden of North Americans was tested, in addition to the technical mixture DE-71 and the individual congener BDE-47. The mixture, DE-71, and BDE-47 all induced adipocyte differentiation as assessed by markers for terminal differentiation [fatty acid binding protein 4 (aP2) and perilipin] and lipid accumulation. Characterization of the differentiation process in response to PBDEs indicated that adipogenesis induced by a minimally effective dose of DEX was enhanced by these PBDEs. Moreover, C/EBPα, PPARγ, and LXRα were induced late in the differentiation process. Taken together, these data indicate that adipocyte differentiation is induced by PBDEs; they act in the absence of glucocorticoid and enhance glucocorticoid-mediated adipogenesis.     

深型复合垂直流人工湿地对模拟污水处理厂尾水中PBDEs的去除研究

研究以四溴联苯醚(BDE-47)为目标污染物,构建了两套深型复合垂直流人工湿地小试系统(IVCW,总基质层高=180 cm)。在固定水力停留时间(HRT=3d)和水力负荷(0.3 m/d)条件下,分析测定其对BDE-47(进水浓度=25μg/L)的分段去除率,并探讨PBDEs加入对IVCW系统常规净化效果与基质微生物的影响。批实验结果表明,运行3个月后, IVCW对模拟污水中BDE-47去除率达到99.9%。与对照组相比, BDE-47处理组对氨氮的去除率由72.3%提高至82.9%,但对硝态氮的去除率显著下降,由53.0%降至28.1%,化学需氧量(COD)去除率由88.1%降至82.3%。IVCW各单元基质中BDE-47的残留量沿水流方向逐渐递减,在距离入流最近的下行流上层单元中BDE-47含量最高(约0.01μg/g);但BDE-47的加入导致基质微生物脱氢酶活性明显降低。微生物特征脂肪酸分析结果表明,实验组与对照组下行流单元微生物群落组成差异明显,分别以具有耐受型较强的微生物如革兰氏阳性厌氧菌和快速生长的好氧型革兰氏阴性菌为主。探究IVCW对BDE-47的去除潜力及迁移转化规律...     

Electron-induced reductive debromination of 2,3,4-tribromodiphenyl ether: a computational study

To better understand the mechanism of the electron induced elimination of the bromide anion, we examined at the B3LYP/6-31+G(d) level electron capture by 2,3,4-tribromodiphenyl ether (BDE-21) followed by the release of the bromide anion and a radical. Both the geometry and energy of the BDE-21 neutral and its possible anionic states were studied. A significant relationship was found between the total energy and the length of the C-Br bonds by the analysis of the potential energy surface for the anionic states. Debromination preference for the bromine substituted positions was theoretically evaluated as meta-Br?>?ortho-Br?>?para-Br. The reaction profiles of the electron-induced debromination of BDE-21 demonstrated that, in general, the presence of a solvent makes the electron induced reductive debromination of BDE-21 significantly more advantageous, and the stabilization effect of the solvent on the reaction intermediates would make the electron attachment and dissociation relatively effective in comparison with the results from the gas-phase calculations.     

Culturable and metagenomic approaches of wheat bran and wheat straw phyllosphere’s highlight new lignocellulolytic microorganisms

The phyllosphere, defined as the aerial parts of plants, is one of the most prevalent microbial habitats on earth. The microorganisms present on the phyllosphere can have several interactions with the plant. The phyllosphere represents then a unique niche where microorganisms have evolved through time in that stressful environment and may have acquired the ability to degrade lignocellulosic plant cell walls in order to survive to oligotrophic conditions. The dynamic lignocellulolytic potential of two phyllospheric microbial consortia (wheat straw and wheat bran) has been studied. The microbial diversity rapidly changed between the native phyllospheres and the final degrading microbial consortia after 48 h of culture. Indeed, the initial microbial consortia was dominated by the Ralstonia (35·8%) and Micrococcus (75·2%) genera for the wheat bran and wheat straw whereas they were dominated by Candidatus phytoplasma (59%) and Acinetobacter (31·8%) in the final degrading microbial consortia respectively. Culturable experiments leading to the isolation of several new lignocellulolytic isolates (belonging to Moraxella and Atlantibacter genera) and metagenomic reconstruction of the microbial consortia highlighted the existence of an unpredicted microbial diversity involved in lignocellulose fractionation but also the existence of new pathways in known genera (presence of CE2 for Acinetobacter, several AAs for Pseudomonas and several GHs for Bacillus in different metagenomes-assembled genomes). The phyllosphere from agricultural co-products represents then a new niche as a lignocellulolytic degrading ecosystem.     

Response of 1,2-dichloroethane-adapted microbial communities to ex-situ biostimulation of polluted groundwater

The microbial community of a groundwater system contaminated by 1,2-dichloroethane (1,2-DCA), a toxic and persistent chlorinated hydrocarbon, has been investigated for its response to biostimulation finalized to 1,2-DCA removal by reductive dehalogenation. The microbial population profile of samples from different wells in the aquifer and from microcosms enriched in the laboratory with different organic electron donors was analyzed by ARISA (Amplified Ribosomal Intergenic Spacer Analysis) and DGGE (Denaturing Gradient Gel Electrophoresis) of 16S rRNA genes. 1,2-DCA was completely removed with release of ethene from most of the microcosms supplemented with lactate, acetate plus formate, while cheese whey supported 1,2-DCA dehalogenation only after a lag period. Microbial species richness deduced from ARISA profiles of the microbial community before and after electron donor amendments indicated that the response of the community to biostimulation was heterogeneous and depended on the well from which groundwater was sampled. Sequencing of 16S rRNA genes separated by DGGE indicated the presence of bacteria previously associated with soils and groundwater polluted by halogenated hydrocarbons or present in consortia active in the removal of these compounds. A PCR assay specific for Desulfitobacterium sp. showed the enrichment of this genus in some of the microcosms. The dehalogenation potential of the microbial community was confirmed by the amplification of dehalogenase-related sequences from the most active microcosms. Cloning and sequencing of PCR products indicated the presence in the metagenome of the bacterial community of a new dehalogenase potentially involved in 1,2-DCA reductive dechlorination.     

Automated solid-phase extraction for the determination of polybrominated diphenyl ethers and polychlorinated biphenyls in serum--application on archived Norwegian samples from 1977 to 2003

An analytical method comprised of automated solid-phase extraction and determination using gas chromatography mass spectrometry (single quadrupole) has been developed for the determination of 12 polybrominated diphenyl ethers (PBDEs), 26 polychlorinated biphenyls (PCBs), two organochlorine compounds (OCs) (hexachlorobenzene and octachlorostyrene) and two brominated phenols (pentabromophenol, and tetrabromobisphenol-A (TBBP-A)). The analytes were extracted using a sorbent of polystyrene-divinylbenzene and an additional clean-up was performed on a sulphuric acid-silica column to remove lipids. The method has been validated by spiking horse serum at five levels. The mean accuracy given as recovery relative to internal standards was 95%, 99%, 93% and 109% for the PBDEs PCBs, OCs and brominated phenols, respectively. The mean repeatability given as RSDs was respectively 6.9%, 8.7%, 7.5% and 15%. Estimated limits of detection (S/N=3) were in the range 0.2-1.8 pg/g serum for the PBDEs and phenols, and from 0.1 pg/g to 56 pg/g serum for the PCBs and OCs. The validated method has been used to investigate the levels of PBDEs and PCBs in 21 pooled serum samples from the general Norwegian population. In serum from men (age 40-50 years) the sum of seven PBDE congeners (IUPAC No. 28, 47, 99, 100, 153, 154 and 183) increased from 1977 (0.5 ng/g lipids) to 1998 (4.8 ng/g lipids). From 1999 to 2003 the concentration of PBDEs seems to have stabilised. On the other hand, the sum of five PCBs (IUPAC No. 101, 118, 138, 153 and 180) in these samples decreased steadily from 1977 (666 ng/g lipids) to 2003 (176 ng/g lipids). Tetrabromobisphenol-A and BDE-209 were detected in almost all samples, but no similar temporal trends to that seen for the PBDEs were observed for these compounds, which might be due to the short half-lives of these brominated flame retardants (FR) in humans.     

Microbial communities from Arctic marine sediments respond slowly to methane addition during ex situ enrichments

Anaerobic methanotrophic archaea (ANME) consume methane in marine sediments, limiting its release to the water column, but their responses to changes in methane and sulfate supplies remain poorly constrained. To address how methane exposure may affect microbial communities and methane- and sulfur-cycling gene abundances in Arctic marine sediments, we collected sediments from offshore Svalbard that represent geochemical horizons where anaerobic methanotrophy is expected to be active, previously active, and long-inactive based on reaction-transport biogeochemical modelling of porewater sulfate profiles. Sediment slurries were incubated at in situ temperature and pressure with different added methane concentrations. Sediments from an active area of seepage began to reduce sulfate in a methane-dependent manner within months, preceding increased relative abundances of anaerobic methanotrophs ANME-1 within communities. In previously active and long-inactive sediments, sulfur-cycling Deltaproteobacteria became more dominant after 30 days, though these communities showed no evidence of methanotrophy after nearly 8 months of enrichment. Overall, enrichment conditions, but not methane, broadly altered microbial community structure across different enrichment times and sediment types. These results suggest that active ANME populations may require years to develop, and consequently microbial community composition may affect methanotrophic responses to potential large-scale seafloor methane releases in ways that provide insight for future modelling studies.