Ligninase-Mediated Removal of Natural and Synthetic Estrogens from Water: I. Reaction Behaviors

Our experiments revealed that a few natural and synthetic estrogens can be effectively transformed through reactions that are mediated by lignin peroxidase (LiP), an extracellular enzyme that is produced by a white rot fungus Phanerochaete chrysosporium and is widely present in the natural environment. We systematically assessed the reaction efficiencies at varying important conditions and identified the reaction products using mass spectrometry. In particular, we compared the reaction behaviors for systems variously containing natural organic matter and/or veratryl alcohol, a secondary metabolite that P. chrysosporium produces along with LiP in nature to play a role in mediating LiP activity. On the basis of the observed reaction behaviors and the molecular characteristics of the substrates and the enzyme, we postulate that the active binding site for estrogens is located within the LiP heme cavity, whereas that for veratryl alcohol is on the enzyme surface. Our study suggests that the processes mediated by LiP and other naturally occurring enzymes of similar nature may influence the environmental transformation and fate of estrogen contaminants. The findings in this study provide useful information for understanding LiP-mediated estrogen reactions and for potential development of novel enzymatic method to control estrogen contamination

Understanding Ligninase-Mediated Reactions of Endocrine Disrupting Chemicals in Water: Reaction Rates and Quantitative Structure–Activity Relationships

We have verified in our previous work that lignin peroxidase (LiP) mediates effective removal of selected natural and synthetic estrogens. The efficiency of these reactions was greatly enhanced in the presence of veratryl alcohol (VA), a chemical that is produced along with LiP by certain white rot fungi, for example, Phanerochaete chrysosporium. In this study, we systematically evaluated the kinetic behaviors of LiP-mediated reactions for six endocrine disrupting compounds (EDCs), that is, steroid estrogens and their structural analogs, in both the presence and absence of VA. Resulting kinetic parameters were then correlated with structural features of LiP/substrate binding complexes, as quantified using molecular simulation, to create quantitative structure–activity relationship (QSAR) equations. These equations suggest that binding distance between a substrate’s phenolic proton and δN of HIS47′s imidazole ring plays an important role in modulating substrate reactivity toward LiP in both the presence and absence of VA. This information provides insight into an important enzymatic reaction process that occurs in the natural environment affecting EDC transformation, a process that may be used in engineered systems to achieve EDC removal from water

Correlations of Gut Microbial Community Shift with Hepatic Damage and Growth Inhibition of <i>Carassius auratus</i> Induced by Pentachlorophenol Exposure

Goldfish (<i>Carassius auratus</i>) were exposed to 0–100 μg/L pentachlorophenol (PCP) for 28 days to investigate the correlations of fish gut microbial community shift with the induced toxicological effects. PCP exposure caused accumulation of PCP in the fish intestinal tract in a time- and dose-dependent manner, while hepatic PCP reached the maximal level after a 21 day exposure. Under the relatively higher PCP stress, the fish body weight and liver weight were reduced and hepatic CAT and SOD activities were inhibited, demonstrating negative correlations with the PCP levels in liver and gut content (<i>R</i> < −0.5 and <i>P</i> < 0.05 each). Pyrosequencing of the 16S rRNA gene indicated that PCP exposure increased the abundance of Bacteroidetes in the fish gut. Within the Bacteroidetes phylum, the <i>Bacteroides</i> genus had the highest abundance, which was significantly correlated with PCP exposure dosage and duration (<i>R</i> > 0.5 and <i>P</i> < 0.05 each). Bioinformatic analysis revealed that <i>Bacteroides</i> showed quantitatively negative correlations with <i>Chryseobacterium</i>, <i>Microbacterium</i>, <i>Arthrobacter</i>, and <i>Legionella</i> in the fish gut, and the Bacteroidetes abundance, <i>Bacteroides</i> abundance, and Firmicutes/Bacteroidetes ratio played crucial roles in the reduction of body weight and liver weight under PCP stress. The results may extend our knowledge regarding the roles of gut microbiota in ecotoxicology

Transformation and Removal of Tetrabromobisphenol A from Water in the Presence of Natural Organic Matter via Laccase-Catalyzed Reactions: Reaction Rates, Products, and Pathways

The widespread occurrence of the brominated flame retardant tetrabromobisphenol A (TBBPA) makes it a possible source of concern. Our experiments suggest that TBBPA can be effectively transformed by the naturally occurring laccase enzyme from <i>Trametes versicolor</i>. These reactions follow second-order kinetics, whereby apparent removal rate is a function of both substrate and enzyme concentrations. For reactions at different initial concentrations and with or without natural organic matter (NOM), reaction products are identified using liquid or gas chromatography with mass spectrometry. Detailed reaction pathways are proposed. It is postulated that two TBBPA radicals resulting from a laccase-mediated reaction are coupled together via interaction of an oxygen atom on one radical and a propyl-substituted aromatic carbon atom on the other. A 2,6-dibromo-4-isopropylphenol carbocation is then eliminated from the radical dimer. All but one of the detected products arise from either substitution or proton elimination of the 2,6-dibromo-4-isopropylphenol carbocation. Three additional products are identified for reactions in the presence of NOM, which suggests that reaction occurs between NOM and TBBPA radical. Data from acute immobilization tests with <i>Daphnia</i> confirm that TBBPA toxicity is effectively eliminated by laccase-catalyzed TBBPA removal. These findings are useful for understanding laccase-mediated TBBPA reactions and could eventually lead to development of novel methods to control TBBPA contamination

Sulfonamide-Resistant Bacteria and Their Resistance Genes in Soils Fertilized with Manures from Jiangsu Province, Southeastern China

<div><p>Antibiotic-resistant bacteria and genes are recognized as new environmental pollutants that warrant special concern. There were few reports on veterinary antibiotic-resistant bacteria and genes in China. This work systematically analyzed the prevalence and distribution of sulfonamide resistance genes in soils from the environments around poultry and livestock farms in Jiangsu Province, Southeastern China. The results showed that the animal manure application made the spread and abundance of antibiotic resistance genes (ARGs) increasingly in the soil. The frequency of sulfonamide resistance genes was <i>sul</i>1 > <i>sul</i>2 > <i>sul</i>3 in pig-manured soil DNA and <i>sul</i>2 > <i>sul</i>1 > <i>sul</i>3 in chicken-manured soil DNA. Further analysis suggested that the frequency distribution of the <i>sul</i> genes in the genomic DNA and plasmids of the SR isolates from manured soil was <i>sul2</i> > <i>sul1</i> > <i>sul3</i> overall (<i>p</i><0.05). The combination of <i>sul</i>1 and <i>sul</i>2 was the most frequent, and the co-existence of <i>sul1</i> and <i>sul3</i> was not found either in the genomic DNA or plasmids. The sample type, animal type and sampling time can influence the prevalence and distribution pattern of sulfonamide resistance genes. The present study also indicated that <i>Bacillus, Pseudomonas</i> and <i>Shigella</i> were the most prevalent <i>sul</i>-positive genera in the soil, suggesting a potential human health risk. The above results could be important in the evaluation of antibiotic-resistant bacteria and genes from manure as sources of agricultural soil pollution; the results also demonstrate the necessity and urgency of the regulation and supervision of veterinary antibiotics in China.</p></div

Prioritization of Veterinary Medicines in China's Environment

<div><p>ABSTRACT</p><p>Large amounts of veterinary medicines are widely used as therapeutic drugs and feed additives (growth promoters) in China, the environmental presence of which possibly poses challenges to the environment and human health. Therefore, it is important to list the veterinary medicines that are considered to be of relatively high priority in China for environmental management. In this study, a three-stage prioritization scheme was applied to veterinary medicines in China. In Stage I, exposure assessment was conducted based on usage amounts and the possibility of entering the environment. In Stage II, the ecotoxicity and human health effects of compounds having a high potential to enter the environment were assessed. In Stage III, considering both the results of Stages I and II, veterinary medicines were assigned into four priority classifications. Using the approach, 38 compounds were assigned to “H,” 7 compounds to “M,” 2 compounds to “L,” and 22 compounds to “VL.” Among the top-ranked compounds, antibiotics, endoparasiticides, and aquacultural medicines accounted for 57.9%, 28.9%, and 10.5%, respectively. Insecticides used widely in China's aquaculture need to be taken into account due to their high priority rank. This is the first study on the prioritization of veterinary pharmaceuticals in China.</p></div

Determination of Phosphite in a Eutrophic Freshwater Lake by Suppressed Conductivity Ion Chromatography

The establishment of a sensitive and specific method for the detection of reduced phosphorus (P) is crucial for understanding P cycle. This paper presents the quantitative evidence of phosphite (P, +3) from the freshwater matrix correspondent to the typically eutrophic Lake Taihu in China. By ion chromatography coupled with gradient elution procedure, efficient separation of micromolar levels of phosphite is possible in the presence of millimolar levels of interfering ions, such as chloride, sulfate, and hydrogen carbonate in freshwater lakes. Optimal suppressed ion chromatography conditions include the use of 500 μL injection volumes and an AS11 HC analytical column heated to 30 °C. The method detection limit of 0.002 μM for phosphite was successfully applied for phosphite determination in natural water samples with recoveries ranging from 90.7 ± 3.2% to 108 ± 1.5%. Phosphite in the freshwater matrix was also verified using a two-dimensional capillary ion chromatography and ion chromatography coupled with mass spectrometry. Results confirmed the presence of phosphite in Lake Taihu ranging from 0.01 ± 0.01 to 0.17 ± 0.01 μM, which correlated to 1–10% of the phosphate. Phosphite is an important component of P and may influence biogeochemical P cycle in lakes

Numbers of cultivable bacteria.

<p>(M = Manure, F = Forest, NA = non-arable fied, P = Pig, C = Chicken, W = winter, V = vegetable garden soil, A = agricultural soil; *p≤0.05, **p≤0.01, n = 3; NS, not significant).</p

Relative quantity of sulfonamides resistant genes in soils with and without manure treatment.

<p>Relative quantity of sulfonamides resistant genes in soils with and without manure treatment.</p