Search

This study investigated the occurrence and variation of 11 antibiotics (including four sulfonamides (SAs), four fluoroquinolones (FQs), two tetracyclines (TCs), and one macrolide (ML)) and one SA synergist trimethoprim (TMP) in an artificial drinking water source reservoir in Yangtze River delta of East China. Water samples were collected each month from January to November in 2014 at the water inlet and outlet site of the reservoir. Sulfamethoxazole, sulfadiazine, and norfloxacin were detected with the high frequencies of 100, 92.31, and 97.85%, respectively. The total concentration showed the highest level in winter (229.14 ng/L) and the lowest one in summer (96.11 ng/L). FQs and TCs were the dominant species among all the antibiotics. The total amount of antibiotics detected in this reservoir showed a negative relationship with temperature (R2 = 0.7565) in this area. From the inlet site to outlet site of this reservoir, all SAs as well as TMP showed decline trends in the four seasons, but other antibiotics including FQs, TCs, and MLs increased more or less in different seasons, especially for ciprofloxacin in winter (from 48.82 ng/L at inlet site to 80.36 ng/L at outlet site). Most antibiotics detected in this drinking water source reservoir had no direct health risk for human with different age groups (except ciprofloxacin for the group of 0–3 months), but still showed obvious ecological risk for algae and invertebrate. Among the three target organisms (algae, invertebrate, and fish), algae was the most sensitive for antibiotics, which was followed by invertebrate. Among the target antibiotics, sulfamethoxazole, ciprofloxacin, tetracycline, and oxytetracycline showed high ecological risk for algae (RQs > 1), and oxytetracycline also showed high risk for invertebrate (RQ = 1.34).

3-Hydroxybenzoate 6-hydroxylase, an NADH-dependent flavoprotein, can convert 3-hydroxybenzoate which is an important intermediate in the biodegradation of many aromatic hydrocarbons. 3-Hydroxybenzoate is metabolized by entering the TCA cycle through the gentisate pathway. We found a putative 3HB6H gene from a cluster that potentially encodes for gentisic acid degradation from a halophilic Martelella sp. strain AD-3. The corresponding protein was expressed with an N-terminal His-tag and purified by Ni2+-nitrilotriacetic acid affinity chromatography. The protein showed an overexpressed band of about 46 kDa by SDS–PAGE, and it was also proven that the enzyme contains FAD by absorption spectroscopy and HPLC analysis. The optimal activity of 3HB6H from strain AD-3 was observed in phosphate buffer (pH 8.0) at 37°C without salinity (NaCl) and metal salts. The Km values of 3-hydroxybenzoate 6-hydroxylase were determined to be 72.6 ± 10.1 μM and 104.1 ± 18.2 μM for 400 μM NADH and 3-hydroxybenzoate, respectively. Site-directed mutagenesis showed that residues 305, 306 and 308 are important for FAD binding. In addition, we found that Tyr221 and Gln305 of 3HB6H from strain AD-3 are involved in substrate binding.

Organic chloramines can interfere with the measurement of effective combined chlorine in chlorinated water and are potential intermediate products of highly toxic disinfection by-products (DBPs). In order to know more about the degradation and transformation of organic chloramines, a typical organic chloramine precursor creatinine was selected for investigation and a corresponding individual organic chloramine chlorocreatinine was prepared in this study. The preparation condition of chlorocreatinine by chlorination was established as chlorine/creatinine = 1 M/M, reaction time = 2 h and pH = 7.0. Then the degradation kinetics of chlorocreatinine during further chlorination was studied, and a second-order rate constant of 1.16 (±0.14) M−1 s−1 was obtained at pH 7.0. Solution pH significantly influenced the degradation rate, and the elementary rate constants of chlorocreatinine with HOCl+H+, HOCl, OCl− and chlorocreatinine− with OCl− were calculated as 2.43 (±1.55) × 104 M−2 s−1, 1.05 (±0.09) M−1 s−1, 2.86 (±0.30) M−1 s−1 and 3.09 (±0.24) M−1 s−1, respectively. Besides, it was found that chlorocreatinine could be further converted into several C-DBPs (chloroform and trichloroacetone) and N-DBPs (dichloroacetonitrile (DCAN) and trichloronitromethane (TCNM)) during chlorination. The total yield of DBPs increased obviously with increasing pH, especially for TCNM. In addition, the presence of humic acid in creatinine solution could increase the formation of DCAN obviously during chlorination. Based on the UPLC-Q-TOF-MS analysis, the conversion pathways of chlorocreatinine were proposed. Several kinds of intermediate products were also identified as organic chloramines and some of them could even exist stably during the further chlorination.

Antibiotics residues in aquatic environments has aroused great public concern since they cannot be effectively removed by conventional biological degradation. Sunlight-driven photo-degradation has been recognized as one of most efficient approach for the antibiotics removal. Herein, we proposed a novel strategy of simultaneous light-harvesting and electron-relay-penetration for the photocatalytic degradation of target antibiotics of ofloxacin (OFL). By incorporating visible-light responded semiconductor CdS nanoparticles into MOF and encapsulating by excellent conductor rGO thin sheets, a series of mesoporous composites of UiO-67/CdS/rGO-x were developed. As a result, the obtained UiO-67/CdS/rGO-1 showed the highest OFL degradation efficiency of 93.4% within 30 min for a 10 ppm OFL solution under the simulated sunlight, in which the turnover frequency (TOF) of 5.44 × 10−3 g(OFL) min−1 g(Cat.)−1 showed an order of magnitude increase over the relevant works. The mechanism study revealed the superoxide radicals O2− and photo-generated hole h+ were the excitons for the photocatalytic oxidation. The equalized Fermi level of UiO-67/CdS heterojunctions was formed to facilitate the electrons relaying, spilling-over, and penetrating through wrapped thin-layered rGO; meanwhile, the selective adsorption of OFL synergistically enhanced the photocatalysis, and hence provided a promising strategy for environmental remediation.

Excessive sulfonamides accumulated in soil and groundwater seriously menace the ecological environment and human health. The performance of a Fenton-like system applying Fe3+ and calcium peroxide (CaO2) in the presence of l-cysteine(l-cys) for sulfadiazine (SDZ) degradation was investigated. Compared with other chelating agents such as citric acid, butyric acid and Ethylenediaminetetraacetic acid, l- cys could effectively promote the SDZ removal in Fe3+/CaO2 system. With the addition of 0.5 mM l-cys, the SDZ degradation increased from 2.14% to 66.53% in 60 min. High concentration of HCO3− inhibited the degradation of SDZ while slightly negative effects on SDZ degradation were observed in the presence of Cl− or humic acid (HA) in l-cys/Fe3+/CaO2 system. Electron paramagnetic resonance (EPR) analysis and radicals scavenge tests affirmed the generation of OH and O2- in l-cys/Fe3+/CaO2 system. Possible degradation pathway of SDZ was speculated and the toxicity of SDZ intermediates was further evaluated. l-cys could enhance the reduction of Fe3+ to Fe2+ and reduced the Fe3+ precipitation due to the l- cys could form stable complexes with Fe3+. l- cys/Fe3+/CaO2 system exhibited high mineralization ability. Overall, these results indicated that l- cys is a promising chelating agent for sulfadiazine wastewater treatment.

Anthracene (40 mg l −1 ) was completely depleted by Martelella sp. strain AD-3 under 3% salinity and a pH of 9.0 after 6 days of incubation. The metabolites were extracted and identified by high-performance liquid chromatography (HPLC) retention times, mass spectrometry, 1 H and 13 C nuclear magnetic resonance spectrometry, and comparison to authentic compounds or literature data. On the basis of the identified metabolites, enzyme activities and the utilization of probable intermediates, anthracene degradation by strain AD-3 is proposed via two distinct routes. In route I, metabolism of anthracene is initiated by the dioxygenation at C-1,2, then proceeds through 6,7-benzocoumarin, 3-hydroxy-2-naphthoic acid, salicylic acid and gentisic acid. In route II, anthracene is metabolized to 9,10-anthraquinone. The results suggest that strain AD-3 possesses efficient anthracene biodegradability in high salinity. To our knowledge, this work presents the first report of anthracene degradation by a halophilic PAH-degrading strain via two routes. The strain AD-3 may be a useful candidate for PAH-contaminated saline-alkali soil bioremediation.

Bioremediation of co-contamination by polycyclic aromatic hydrocarbons (PAHs) and arsenite (As (III)) may be a cost-effective alternative to conventional chemical removal methods. In this study, a heterotrophic bacterial consortium capable of simultaneously degrading PAHs and oxidizing As (III) has been isolated. After 48 h of incubation, the bacterial consortium removed 71.4% of PHE and transformed 96.2% of As (III) to arsenate (As (V)) in liquid culture containing 200 mg l−1 of PHE and 60 mg l−1 of As (III) under aerobic conditions. A 16S rDNA library was constructed from the consortium to identify the dominant bacteria, which were Pseudomonas, Pusillimonas, Alcaligenes and Achromobacter spp. DGGE profiles showed considerable differences in community structure as the ratio of PHE and As (III) changed. When both PHE and As (III) were present, bacteria from the γ-Proteobacteria group (Pseudomonas) and β-Proteobacteria group (Achromobacter and Alcaligenes) were abundant. However, when only PHE was present, Pseudomonas and Achromobacter spp. were dominant, and when only As (III) was present, Pseudomonas and Alcaligenes spp. were the dominant species. The use of the dually functioning bacterial consortium provides a potential application for efficient biotransformation of PAHs and arsenite co-contamination systems.

Waste electrical and electronic equipment (e-waste) is now the fastest growing waste stream in the world. It is reported that polybrominated diphenyl ethers (PBDEs) and heavy metals were main contaminants in e-waste recycling site. Among these contaminants BDE-209 and Cu were widespread, yet their combined effect on soil enzyme activities and microbial community structure are not well understood. In this study, the ecotoxicological effects of both combined and single pollution of BDE-209 and Cu at different concentration levels were studied under laboratory conditions. The activities of soil catalase, urease and saccharase were sensitive to BDE-209 and Cu pollution. Although the enzyme activities varied over time, the concentration effects were obvious. Statistical analyses revealed that, at the same incubation time, as the concentration of BDE-209 or Cu increased, the enzyme activities were decreased. Combined effects of both BDE-209 and Cu were different from that of BDE-209 or Cu alone. Enzyme activities data were essentially based on the multiple regression technique. The results showed that the action and interaction between BDE-209 and Cu were strongly dependent on the exposure time, as the combined effects of BDE-209 and Cu were either synergistic or antagonistic at different incubation times. Soil catalase and saccharase were more comfortable used as indicators of BDE-209 and Cu combined pollution, as the variation trends were similar to the single contaminant treatments, and the responses were quick and significant. Denaturing Gradient Gel Electrophoresis (DGGE) analysis of bacterial 16S rDNA gene showed that BDE-209 and Cu pollution altered the bacterial community structure by promoting changes in species composition and species richness. The existence of BDE-209 and Cu in soils reduced the microbial diversity, and the concentration effects were obvious. Overall, microbial diversity in the combined treatments were lower than the single ones, and when the concentration of BDE-209 and Cu increased, and the Shannon–Weaver index decreased, which indicated the combined effect of BDE-209 and Cu on the microbial community structure was synergistic. Our results further the understanding of the toxic effects of BDE-209 and Cu on soil enzyme activities and microbial community structure, and suggest the need for more in-depth analysis to increase progressively the understanding of the toxicological mechanisms involved.

The ecotoxicological effects of decabromodiphenyl ether (BDE209) and cadmium (Cd) contamination on soil culturable microbial population, enzyme activity and bacterial community structure were investigated. Results of the indoor incubation test runs performed on many series of control and contaminated soil samples have demonstrated some notable toxic effects due to long term exposure to either or both contaminants. The two contaminants produced notable yet different toxic effects on the test microbes; the population of the exposed species generally declined according to certain dose–response relationships. The soil culturable microbial population and enzyme activity data show that the sensitivity to one or both contaminants followed the order of: bacteria>fungi>actinomycete and urease>saccharase, respectively. The interaction between BDE209 and Cd was dependent on both the exposure dose and time and that the joint toxic effects were synergistic, antagonistic or additive. The PCR-DGGE analysis data of species composition and richness suggest the synergistic combined effects on bacterial community structure during the 30 d exposure. Pseudomonas tuomuerensis strain CCM 7280 and Pseudomonas alcaliphila strain AL15-21 were enriched, indicating these species might be major functional populations and highly tolerant. Such observations have provided the useful information of potential ecotoxicological effects of BDE209 and Cd contamination in the environment.

Aims To investigate the phenanthrene-degrading abilities of the halophilic Martelella species AD-3 under different conditions and to propose a possible metabolic pathway. Methods and Results Using HPLC and GC-MS analyses, the phenanthrene-degrading properties of the halophilic strain AD-3 and its metabolites were analysed. This isolate efficiently degraded phenanthrene under multiple conditions characterized by different concentrations of phenanthrene (100–400 mg l−1), a broad range of salinities (0·1–15%) and varying pHs (6·0–10·0). Phenanthrene (200 mg l−1) was completely depleted under 3% salinity and a pH of 9·0 within 6 days. The potential toxicity of phenanthrene and its generated metabolites towards the bacterium Vibrio fischeri was significantly reduced 10 days after the bioassay. On the basis of the identified metabolites, enzyme activities and the utilization of probable intermediates, phenanthrene degradation by strain AD-3 was proposed in two distinct routes. In route I, metabolism of phenanthrene was initiated by the dioxygenation at C-3,4 via 1-hydroxy-2-naphthoic acid, 1-naphthol, salicylic acid and gentisic acid. In route II, phenanthrene was metabolized to 9-phenanthrol and 9,10-phenanthrenequinone. Further study indicated that strain AD-3 exhibited a wide spectrum of substrate utilization including other polycyclic aromatic hydrocarbons (PAHs). Conclusions The results suggest that strain AD-3 possesses a high phenanthrene biodegradability and that the degradation occurs via two routes that remarkably reduce toxicity. Significance and Impact of the Study To the best of our knowledge, this work presents the first report of phenanthrene degradation by a halophilic PAH-degrading strain via two routes. In the future, the use of halophilic strain AD-3 provides a potential application for efficient PAH-contaminated hypersaline field remediation.

Previous reports showed that Escherichia coli (E. coli) undergone an electrochemical activation process can catalyze glucose oxidation in microbial fuel cell (MFC) in the absence of extraneous mediators [T. Zhang, C.Z. Cui, S.L. Chen, X.P. Ai, H.X. Yang, P. Shen, Z.R. Peng, Chem. Commun. (2006) 2257; T. Zhang, Y.L. Zeng, S.L. Chen, X.P. Ai, H.X. Yang, Electrochem. Commun. 9 (2007) 349]. This paper investigates the electron transfer mechanism associated with the direct bioelectrocatalysis of electroactivated E. coli in MFC. It is shown that covering the electrode surface with a filter membrane with pore smaller than the size of E. coli cells hardly changes the fuel cell discharge behaviors and the voltammetric responses in the culture of electroactivated E. coli, indicating that the electron transfer between the electrode and E. coli cells is carried out by soluble compounds in the culture. The GC–MS results indicate that these compounds are excreted by E. coli in MFC, i.e., they are exploitable metabolites. Keywords: Microbial fuel cell, Escherichia coli, Extracellular electron transfer, Bioelectrocatalysis, Metabolites as electron mediators

Martelella sp. strain AD-3, a moderate halophilic bacterium, was isolated from a petroleum-contaminated soil with high salinity in China. Here, we report the complete genome of strain AD-3, which contains one circular chromosome and two circular plasmids. An array of genes related to metabolism of polycyclic aromatic hydrocarbons and halophilic mechanism in this bacterium was identified by the whole genome analysis.

Halophilic Martelella strain AD-3, isolated from highly saline petroleum-contaminated soil, can efficiently degrade polycyclic aromatic hydrocarbons (PAHs), such as phenanthrene and anthracene, in 3–5% salinity. Gentisic acid is a key intermediate in the microbial degradation of PAH compounds. However, there is little information on PAH degradation by moderately halophilic bacteria. In this study, a 1,077-bp long gene encoding gentisate 1,2-dioxygenase (GDO) from a halophilic Martelella strain AD-3 was cloned, sequenced and expressed in Escherichia coli. The recombinant enzyme GDO was purified and characterized in detail. By using the 18O isotope experiment and LC-MS analysis, the sources of the two oxygen atoms added onto maleylpyruvate were identified as H2O and O2, respectively. The Km and kcat values for gentisic acid were determined to be 26.64 μM and 161.29 s−1, respectively. In addition, optimal GDO activity was observed at 30 °C, pH 7.0 and at 12% salinity. Site-directed mutagenesis demonstrated the importance of four highly conserved His residues at positions 155, 157, 167 and 169 for enzyme activity. This finding provides new insights into mechanism and variety of gentisate 1,2-dioxygenase for PAH degradation in high saline conditions.

Martelella sp. strain AD-3, enriched from a petroleum-contaminated site with high salinity, can efficiently degrade polycyclic aromatic hydrocarbons. Here, we report the 4.75-Mb genome sequence of strain AD-3 with its genetic feature of helping to remediate environmental organic pollutants.

Lead (Pb) and decabromodiphenyl ether (BDE209) are the main contaminants at e-waste recycling sites, and their potential toxicological effects on terrestrial organisms have received extensive attention. However, the impact on earthworms of exposure to the two chemicals remains almost unknown. Therefore, indoor incubation tests were performed on control and contaminated soil samples to determine the Pb accumulations and toxic effects by earthworms in the presence of BDE209 for the first time. The results have demonstrated that BDE209 presence can affect Pb bioaccumulation efficiency compared with exposure to Pb alone. The Pb contents in earthworms had a highly positive correlation with the Pb concentrations in soils. For different Pb doses, almost contrary response trends were found for Pb uptake examined separately on day 7 or 28, and dose-effect relationships were clearly observed in the presence of BDE209. After 7 days of exposure, the earthworm bodies receiving 1-mg kg(-1) BDE209 dose showed significantly lower Pb contents (average = 175.85 mg kg(-1)) and bioaccumulation factor (average = 0.574) than those receiving non-BDE209 treatments (217.39 mg kg(-1) and 1.209, respectively). As the incubation time extended, the influence of BDE209 presence on Pb uptake gradually declined. Additionally, either single or combined exposure to both chemicals can affect the protein synthesis in earthworms (p 0.01), while different levels of BDE209 addition barely caused visible differences. The results of these observations have provided a basic understanding on the potential toxicological effects of joint Pb and BDE209 exposure on terrestrial invertebrates.

To identify the relationship between salicylate 5-hydroxylase activity and the degradation rate of phenanthrene by moderately halophilic Martelella sp. AD-3, and to investigate their enzymatic characteristics.The products resulted from degradation of salicylic acid using the crude enzyme produced by AD-3 was analyzed using HPLC analysis, and salicylate 5-hydroxylase activities at different conditions was calculated according to the change of NADH absorbance at 340 nm.The salicylate 5-hydroxylase activity was higher during log-phase and early stationary phase of AD-3, and the enzyme activity was in consistent with phenanthrene degradation rate. The enzyme production was induced by phenanthrene and salicylic acid. The highest enzyme activity, 132.8 nmol/(min x mg), from strain AD-3 was obtained under the phenanthrene concentration of 200 mg/L, 3% salinity and a pH of 9.0. The optimum conditions for degradation of salicylic acid using this enzyme were 30 degrees C , pH 7.5, and salinity 3%. The V(max) and K(m) for the enzyme were 200 nmol/(min x mg) and 8.7 micromol/L, respectively.The salicylate 5-hydroxylase was produced in the degradation of phenanthrene in AD-3. The enzyme activity was related to phenanthrene degradation rate.

In this paper, we study H-infinity performance for the switched systems with continuous-time and discrete-time subsystems. By using common quadratic Lyapunov function technology and LMI approach, the sufficient condition is given in form of LMI for the problem that such switched systems are stabilization with H ∞ disturbance attenuation level γ via arbitrary switching. Finally, a numerical example is given to validate our results.

In this paper, we address the problem of robust stabilization and disturbance rejection for a class of hybrid linear systems subject to exponential uncertainties. By using Taylor series approximation and convex polytope technique, the exponentially uncertain hybrid linear system is transformed into an equivalent hybrid polytopic model subject to norm bounded uncertainty. For such equivalent hybrid linear model, we design its switching strategy and associated state feedback controllers so that such model is asymptotically stable with H∞ disturbance attenuation based on multiple Lyapunov function technology and linear matrix inequality (LMI) approach.

Oxcarbazepine (OXC) is widely used nowadays due to its similar therapeutic effects of carbamazepine (CBZ) but with fewer side effects. The prescribed consumption of OXC has increased significantly in some countries, and its environmental pollutions have become a major concern. This paper firstly reported the degradation of OXC by heat-activated persulfate. Effects of temperature, dosage of persulfate and pH on the oxidation of OXC were examined. OXC degradation followed a pseudo-first-order decay model. The rate of OXC oxidation rose with the increase of persulfate (2.0 mM to 6.0 mM) and pH (5.0 to 9.0). OXC can be oxidised almost completely within 10 min by persulfate (4.0 mM, pH 9.0, 50°C). HO·was the major active free radical, 9-oxo-9, 10-dihydroacridine-4-carbaldehyde and 9, 10-dihydroacridine-9-carbaldehyde were the major intermediates of OXC degradation by heat-activated persulfate. The heat-activated persulfate demonstrating high potential for the degradation of OXC, is a promising technique for its removal.

A mediatorless microbial fuel cell based on the direct biocatalysis of Escherichia coli shows significantly enhanced performance by using bacteria electrochemically-evolved in fuel cell environments through a natural selection process and a carbon/PTFE composite anode with an optimized PTFE content.