Accurate Prediction of Rat Acute Oral Toxicity and Reference Dose for Thousands of Polycyclic Aromatic Hydrocarbon Derivatives Based on Chemometric QSAR and Machine Learning.

Acute oral toxicity is currently not available for most polycyclic aromatic hydrocarbons (PAHs), especially their derivatives, because it is cost-prohibitive to experimentally determine all of them. Here, quantitative structure-activity relationship (QSAR) models using machine learning (ML) for predicting the toxicity of PAH derivatives were developed, based on oral toxicity data points of 788 individual substances of rats. Both the individual ML algorithm gradient boosting regression trees (GBRT) and the stacking ML algorithm (extreme gradient boosting + GBRT + random forest regression) provided the best prediction results with satisfactory determination coefficients for both cross-validation and the test set. It was found that those PAH derivatives with fewer polar hydrogens, more large-sized atoms, more branches, and lower polarizability have higher toxicity. Software based on the optimal ML-QSAR model was successfully developed to expand the application potential of the developed model, obtaining reliable prediction of pLD50 values and reference doses for 6893 external PAH derivatives. Among these chemicals, 472 were identified as moderately or highly toxic; 10 out of them had clear environment detection or use records. The findings provide valuable insights into the toxicity of PAHs and their derivatives, offering a standard platform for effectively evaluating chemical toxicity using ML-QSAR models.

Biosynthesis of magnetosome-nanobody complex in Magnetospirillum gryphiswaldense MSR-1 and a magnetosome-nanobody-based enzyme-linked immunosorbent assay for the detection of tetrabromobisphenol A in water.

In this study, two mutant strains, TBC and TBC+, able to biosynthesize a novel functional magnetosome-nanobody (Nb), were derived from the magnetotactic bacteria Magnetospirillum gryphiswaldense MSR-1. The magnetosome-Nbs biosynthesized by TBC+ containing multi-copies of the Nb gene had a higher binding ability to an environmental pollutant, tetrabromobisphenol A (TBBPA), than those biosynthesized by TBC containing only one copy of the Nb gene. The magnetosome-Nbs from TBC+ can effectively bind to TBBPA in solutions with high capacity without being affected by a broad range of NaCl and methanol concentrations as well as pH. Therefore, a magnetosome-Nb-based enzyme-linked immunosorbent assay (ELISA) was developed and optimized for the detection of TBBPA, yielding a half-maximum signal inhibition concentration of 0.23 ng/mL and a limit of detection of 0.025 ng/mL. The assay was used to detect TBBPA in spiked river water samples, giving average recoveries between 90 and 120% and coefficients of variation of 2.5-6.3%. The magnetosome-Nb complex could be reused 4 times in ELISA without affecting the performance of the assay. Our results demonstrate the potential of magnetosome-Nbs produced by TBC+ as cost-effective and environment-friendly reagents for immunoassays to detect small molecules in environmental waters.

Neuroprotection of isoorientin against microglia activation induced by lipopolysaccharide via regulating GSK3ß, NF-κb and Nrf2/HO-1 pathways.

Background: Isoorientin (ISO), a flavone C-glycoside, is a glycogen synthase kinase 3ß (GSK3ß) substrate-competitive inhibitor. ISO has potential in treatment of Alzheimer's disease (AD). An excessive activation of GSK3ß can lead to neuroinflammation causing neuronal damage. Microglia cells, as resident immune cells of the central nervous system, mediate neuroinflammation. Here, we studied the effects of ISO on microglial activation to alleviate neuroinflammation.Methods: Effects of ISO were observed upon the stimulation of mouse microglia BV2 or SIM-A9 cells by lipopolysaccharide (LPS). Lithium chloride (LiCl) was the positive control as a GSK3ß inhibitor. The release of TNF-α and NO were analyzed by ELISA and Griess assays, while expressions of COX-2, Iba-1, BDNF, GSK3ß, NF-κB p65, IκB, Nrf2 and HO-1 were detected by Western blotting. In the co-culture model of SIM-A9 cells and differentiated SH-SY5Y human neuroblastoma cells, effects of ISO on microglia-mediated neuronal damage were evaluated with the MTS assay.Results: ISO significantly inhibited the production of TNF-α (p < 0.01), NO (p < 0.001) and the expression of COX-2 (p < 0.01) and Iba-1 (p < 0.05) induced by LPS, and increased BDNF. The cell viability of SH-SY5Y was inhibited by LPS in the co-culture, which was prevented by ISO pretreatment. ISO increased the expression of p-GSK3ß (Ser9), IκB and HO-1 in the cytoplasm, decreased NF-κB p65 and increased Nrf2 in the nucleus compared with the LPS group.Conclusion: ISO attenuated the activation of microglia through regulating the GSK3ß, NF-κB and Nrf2/HO-1 signaling pathways to exert neuroprotection.

Toxic effects of the insecticide tolfenpyrad on zebrafish embryos: Cardiac toxicity and mitochondrial damage.

Tolfenpyrad, a highly effective and broad-spectrum insecticide and acaricide extensively utilized in agriculture, presents a potential hazard to nontarget organisms. This study was designed to explore the toxic mechanisms of tolfenpyrad on zebrafish embryos. Between 24 and 96 h after exposure of the fertilized embryos to tolfenpyrad at concentrations ranging from 0.001 to 0.016 mg/L (96 h-LC50 = 0.017 mg/L), lethal effects were apparent, accompanied with notable anomalies including pericardial edema, increased pericardial area, diminished heart rate, and an elongated distance between the venous sinus and the arterial bulb. Tolfenpyrad elicited noteworthy alterations in the expression of genes pertinent to cardiac development and apoptosis, with the most pronounced changes observed in the cardiac development-related genes of bone morphogenetic protein 2b (bmp2b) and p53 upregulated modulator of apoptosis (puma). The findings underscore that tolfenpyrad induces severe cardiac toxicity and mitochondrial damage in zebrafish embryos. This data is imperative for a comprehensive assessment of tolfenpyrad risks to aquatic ecosystems, particularly considering the limited knowledge regarding its detrimental impact on aquatic vertebrates.

Development, Evaluation, and Application of Machine Learning Models for Accurate Prediction of Root Uptake of Per- and Polyfluoroalkyl Substances.

Machine learning (ML) models were developed for understanding the root uptake of per- and polyfluoroalkyl substances (PFASs) under complex PFAS-crop-soil interactions. Three hundred root concentration factor (RCF) data points and 26 features associated with PFAS structures, crop properties, soil properties, and cultivation conditions were used for the model development. The optimal ML model, obtained by stratified sampling, Bayesian optimization, and 5-fold cross-validation, was explained by permutation feature importance, individual conditional expectation plot, and 3D interaction plot. The results showed that soil organic carbon contents, pH, chemical logP, soil PFAS concentration, root protein contents, and exposure time greatly affected the root uptake of PFASs with 0.43, 0.25, 0.10, 0.05, 0.05, and 0.05 of relative importance, respectively. Furthermore, these factors presented the key threshold ranges in favor of the PFAS uptake. Carbon-chain length was identified as the critical molecular structure affecting root uptake of PFASs with 0.12 of relative importance, based on the extended connectivity fingerprints. A user-friendly model was established with symbolic regression for accurately predicting RCF values of the PFASs (including branched PFAS isomerides). The present study provides a novel approach for profound insight into the uptake of PFASs by crops under complex PFAS-crop-soil interactions, aiming to ensure food safety and human health.

Mechanism and Association between Microbial Nitrogen Transformation in Rhizosphere and Accumulation of Ciprofloxacin in Choysum (Brassica parachinensis).

Rhizosphere microbiota are an important factor impacting plant uptake of pollutants. However, little is known about how microbial nitrogen (N) transformation in the rhizosphere affects the uptake and accumulation of antibiotics in plants. Here, we determined recruitment of N transformation functional bacteria upon ciprofloxacin (CIP) exposure, by comparing differences in assembly processes of both rhizospheric bacterial communities and N transformation between two choysum (Brassica parachinensis) varieties differing in CIP accumulation. The low accumulation variety (LAV) of CIP recruited more host bacteria (e.g., Nitrospiria and Nitrolancea) carrying nitrification genes (mainly nxrA) but fewer host bacteria carrying denitrification genes, especially narG, relative to the high accumulation variety (HAV) of CIP. The nxrA and narG abundance in the LAV rhizosphere were, respectively, 1.6-7.8 fold higher and 1.4-3.4 fold lower than those in the HAV rhizosphere. Considering that nitrate can decrease CIP uptake into choysum through competing for the proton motive force and energy, such specific bacteria recruitment in LAV favored the production and utilization of nitrate in its rhizosphere, thus limiting its CIP accumulation with 1.6-2.4 fold lower than the HAV. The findings give insight into the mechanism underlying low pollutant accumulation, filling the knowledge gap regarding the profound effects of rhizosphere microflora and N transformation processes on antibiotic accumulation in crops.

Isoorientin Affects Markers of Alzheimer's Disease via Effects on the Oral and Gut Microbiota in APP/PS1 Mice.

BACKGROUND: There is growing evidence of strong associations between the pathogenesis of Alzheimer's disease (AD) and dysbiotic oral and gut microbiota. Recent studies demonstrated that isoorientin (ISO) is anti-inflammatory and alleviates markers of AD, which were hypothesized to be mediated by the oral and gut microbiota. OBJECTIVES: We studied the effects of oral administration of ISO on AD-related markers and the oral and gut microbiota in mice. METHODS: Eight-month-old amyloid precursor protein/presenilin-1 (AP) transgenic male mice were randomly allocated to 3 groups of 15 mice each: vehicle (AP) alone or with a low dose of ISO (AP + ISO-L; 25 mg/kg) or a high dose of ISO (AP + ISO-H; 50 mg/kg). Age-matched wild-type (WT) C57BL/6 male littermates were used as controls. The 4 groups were treated intragastrically with ISO or sterilized ultrapure water for 2 months. AD-related markers in the brain, serum, colon, and liver were analyzed with immunohistochemical and histochemical staining, Western blotting, and ELISA. Oral and gut microbiotas were analyzed using 16S ribosomal RNA gene sequencing. RESULTS: The high-dose ISO treatment significantly decreased amyloid beta 42-positive deposition by 38.1% and 45.2% in the cortex and hippocampus, respectively, of AP mice (P < 0.05). Compared with the AP group, both ISO treatments reduced brain phospho-Tau, phosphor-p65, phosphor-inhibitor of NF-κB, and brain and serum LPS and TNF-α by 17.9%-72.5% and increased brain and serum IL-4 and IL-10 by 130%-210% in the AP + ISO-L and AP + ISO-H groups (P < 0.05). Abundances of 26, 25, and 23 microbial taxa in oral, fecal and cecal samples, respectively, were increased in both the AP + ISO-L and AP + ISO-H groups relative to the AP group [linear discriminant analysis (LDA) >3.0; P < 0.05]. Gram-negative bacteria, Alteromonas, Campylobacterales, and uncultured Bacteroidales bacterium were positively correlated (rho = 0.28-0.59; P < 0.05) with the LPS levels and responses of inflammatory cytokines. CONCLUSIONS: The microbiota-gut-brain axis is a potential mechanism by which ISO reduces AD-related markers in AP mice.

Construction of a novel fluorescent nanocarrier with double hollow shells for pH-controlled release of imidacloprid and its distribution and transport in bok choy.

Nanotechnology has been widely used in the field of pesticides. Integration of nano-pesticides and carbon dot fluorescence can fully utilize the potential for high admission of pesticides on leaves and convenience observation of its distribution and transport in the tissues. In the present study, a fluorescent mesoporous nanosilica with double hollow shells for loading imidacloprid (Im@FL-MSNs) was designed and synthesized. The physical and chemical properties of the imidacloprid nanocarriers were characterized by transmission electron microscopy (TEM), FT-IR spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and N2 adsorption/desorption. When the mass ratio of FL MSNs to imidacloprid is 6:5, Im@FL-MSNs exhibits good fluorescence properties, high loading efficiency (∼30%), great slow-release performance as well as pH controllability. Besides, Im@FL-MSNs can improve the ability of imidacloprid to adhere on the leaf surface of bok choy (Initial contact angled is greater than 80°ï¼‰. Importantly, Im@FL-MSNs did not reduce the biological activity of imidacloprid (LC50 (95% CI) = 1.43 mg/L). It was able to visually study the absorption and distribution of imidacloprid in bok choy plants, and provide theoretical and technical guidance for pesticide reduction.

Dihydromyricetin Imbues Antiadipogenic Effects on 3T3-L1 Cells via Direct Interactions with 78-kDa Glucose-Regulated Protein.

BACKGROUND: Obesity is among the most serious public health problems worldwide, with few safe pharmaceutical interventions. Natural products have become an important source of potential anti-obesity therapeutics. Dihydromyricetin (DHM) exerts antidiabetic effects. The biochemical target of DHM, however, has been unknown. It is crucial to identify the biochemical target of DHM for elucidating its physiological function and therapeutic value. OBJECTIVES: The objective of this study was to identify the biochemical target of DHM. METHODS: An abundant antiadipogenic flavanonol was extracted from the herbal plant Ampelopsis grossedentata through bioassay-guided fractionation and characterized with high-resolution LC-MS and 1H and 13C nuclear magnetic resonance. Antiadipogenic experiments were done with mouse 3T3-L1 preadipocytes. A biochemical target of the chemical of interest was identified with drug affinity responsive target stability assay. Direct interactions between the chemical of interest and the protein target in vitro were predicted with molecular docking and subsequently confirmed with surface plasmon resonance. Expression levels of peroxisome proliferator-activated receptor γ (PPARγ), which is associated with 78-kDa glucose-regulated protein (GRP78), were measured with real-time qPCR. RESULTS: DHM was isolated, purified, and structurally characterized. Cellular studies showed that DHM notably reduced intracellular oil droplet formation in 3T3-L1 cells with a median effective concentration of 294 µM (i.e., 94 µg/mL). DHM targeted the ATP binding site of GRP78, which is associated with adipogenesis. An equilibrium dissociation constant between DHM and GRP78 was 21.8 µM. In 3T3-L1 cells upon treatment with DHM at 50 µM (i.e., 16 µg/mL), the expression level of PPARγ was downregulated to 53.9% of the solvent vehicle control's level. CONCLUSIONS: DHM targets GRP78 in vitro. DHM is able to reduce lipid droplet formation in 3T3-L1 cells through a mode of action that is plausibly associated with direct interactions between GRP78 and DHM, which is a step forward in determining potential applications of DHM as an anti-obesity agent.

Comparison of three palm tree peroxidases expressed by Escherichia coli: Uniqueness of African oil palm peroxidase.

Palm tree peroxidase has greater catalytic activity, stability and broad application prospects in comparison with horseradish peroxidase. However, slow growth, ecological destruction and high costs prohibit isolation of native peroxidases directly from palm trees. Bioreactor production of palm tree peroxidases would therefore be preferred to overcome such production limitations. Comparison of different recombinant glycan-free palm tree peroxidases would allow understanding the criticality of total glycans to the functions and characteristics. In the present study, African oil palm tree peroxidase expressed by Escherichia coli showed similar stability and 30-100-fold greater activity than that of recombinant royal palm tree peroxidases, but both of their comprehensive indexes were superior to the commercial, native horseradish peroxidase. Recombinant Chamaerops excelsa peroxidase showed no activity possibly due to incorrect protein folding. The results confirmed that recombinant expression by E. coli is potentially an effective means to obtain a mass of palm peroxidases with high activity and stability.

Variety-Selective Rhizospheric Activation, Uptake, and Subcellular Distribution of Perfluorooctanesulfonate (PFOS) in Lettuce (Lactuca sativa L.).

Perfluorooctanesulfonate (PFOS) as an accumulative emerging persistent organic pollutant in crops poses severe threats to human health. Lettuce varieties that accumulate a lower amount of PFOS (low-accumulating crop variety, LACV) have been identified, but the regarding mechanisms remain unsolved. Here, rhizospheric activation, uptake, translocation, and compartmentalization of PFOS in LACV were investigated in comparison with those of high-accumulating crop variety (HACV) in terms of rhizospheric forms, transporters, and subcellular distributions of PFOS. The enhanced PFOS desorption from the rhizosphere soils by dissolved organic matter from root exudates was observed with weaker effect in LACV than in HACV. PFOS root uptake was controlled by a transporter-mediated passive process in which low activities of aquaporins and rapid-type anion channels were corrected with low expression levels of PIPs (PIP1-1 and PIP2-2) and ALMTs (ALMT10 and ALMT13) genes in LACV roots. Higher PFOS proportions in root cell walls and trophoplasts caused lower root-to-shoot transport in LACV. The ability to cope with PFOS toxicity to shoot cells was poorer in LACV relative to HACV since PFOS proportions were higher in chloroplasts but lower in vacuoles. Our findings provide novel insights into PFOS accumulation in lettuce and further understanding of multiprocess mechanisms of LACV.

Development of a nanobody-based ELISA for the detection of the insecticides cyantraniliprole and chlorantraniliprole in soil and the vegetable bok choy.

Cyantraniliprole and chlorantraniliprole are anthranilic diamide insecticides acting on ryanodine receptors. In this study, two camel-derived nanobodies (Nbs, named C1 and C2) recognizing cyantraniliprole as well as chlorantraniliprole were generated. C1-based enzyme-linked immunosorbent assays (ELISAs) for the detection of the two insecticides were developed. The half-maximum signal inhibition concentrations (IC50) of cyantraniliprole and chlorantraniliprole by ELISA were 1.2 and 1.5 ng mL-1, respectively. This assay was employed to detect these two insecticides in soil and vegetables. The average recoveries of cyantraniliprole from both bok choy (Brassica chinensis L.) and soil samples were 90-129%, while those of chlorantraniliprole were in a range of 89-120%. The insecticide residues in soil and bok choy, which were collected from plots sprayed with cyantraniliprole and chlorantraniliprole, were simultaneously detected by the resulting ELISA and a high-performance liquid chromatography (HPLC) method, showing a satisfactory correlation. Higher concentrations of chlorantraniliprole than cyantraniliprole were detected in soil and vegetables, which indicates the longer persistence of chlorantraniliprole in the environment.

Interactions of isoorientin and its Semi-synthetic analogs with human serum albumin.

Isoorientin is a C-glycosyl flavone with a wide range of health beneficial effects and inhibits glycogen synthase kinase 3ß (GSK-3ß) potentially against Alzheimer's disease. Its semi-synthetic derivatives have greater potency than isoorientin. The present study was aimed to determine the mechanism of interactions of isoorientin and its derivatives with human serum albumin (HSA) using multi-spectroscopic, microscale thermophoresis (MST) and computational studies. Spectra of steady-state fluorescence, UV-Vis, and time-resolved fluorescence indicated that isoorientin and its derivatives quenched the intrinsic fluorescence of HSA through a static quenching process. Isoorientin and its derivatives had a moderate affinity with HSA (Ka 7.7-14.9 × 104 M-1). The binding process was accompanied by an exothermic phenomenon, ΔG° of HSA-isoorientin and its derivatives systems were calculated as from -29.51 kJ mol-1 to -27.87 kJ mol-1. Displacement experiments with site-specific markers revealed that isoorientin and its derivatives bind to HSA at site II (subdomain IIIA) only. A reduction in the α-helical content of HSA-isoorientin and its derivatives complex was observed, because the conformational changes was structurally perturbed by the hydrophilic groups of the compounds. Further molecular modeling studies confirmed that the binding of isoorientin and its derivatives to the site II via hydrophobic interaction. The MST results confirmed the interactions between HSA and the compounds of interest. The esterase-like assay studies indicated that isoorientin and its derivatives shared the same binding site in HSA, and their induced structural changes of HSA may have been caused by partial unfolding of HSA. This work helps to understand transport, distribution, bioactivity, and design of flavonoid-based GSK-3ß inhibitors.

Fusion expression of nanobodies specific for the insecticide fipronil on magnetosomes in Magnetospirillum gryphiswaldense MSR-1.

BACKGROUND: Magnetic nanoparticles such as magnetosomes modified with antibodies allow a high probability of their interaction with targets of interest. Magnetosomes biomineralized by magnetotactic bacteria are in homogeneous nanoscale size and have crystallographic structure, and high thermal and colloidal stability. Camelidae derived nanobodies (Nbs) are small in size, thermal stable, highly water soluble, easy to produce, and fusible with magnetosomes. We aimed to functionalize Nb-magnetosomes for the analysis of the insecticide fipronil. RESULTS: Three recombinant magnetotactic bacteria (CF, CF+ , and CFFF) biomineralizing magnetosomes with different abundance of Nbs displayed on the surface were constructed. Compared to magnetosomes from the wild type Magnetospirillum gryphiswaldense MSR-1, all of the Nb-magnetosomes biosynthesized by strains CF, CF+ , and CFFF showed a detectable level of binding capability to fipronil-horseradish peroxidase (H2-HRP), but none of them recognized free fipronil. The Nb-magnetosomes from CFFF were oxidized with H2O2 or a glutathione mixture consisting of reduced glutathione and oxidized glutathione in vitro and their binding affinity to H2-HRP was decreased, whereas that to free fipronil was enhanced. The magnetosomes treated with the glutathione mixture were employed to develop an enzyme-linked immunosorbent assay for the detection of fipronil in water samples, with average recoveries in a range of 78-101%. CONCLUSIONS: The economical and environmental-friendly Nb-magnetosomes biomineralized by the bacterial strain MSR-1 can be potentially applied to nanobody-based immunoassays for the detection of fipronil or nanobody-based assays in general.

Enantioselective metabolism of phenylpyrazole insecticides by rat liver microsomal CYP3A1, CYP2E1 and CYP2D2.

The stereoselective difference of chiral pesticide enantiomers is an important factor of risk evaluation and the subject has received wide attention. In the present work, enantioselective metabolism of chiral phenylpyrazole insecticides including fipronil, ethiprole and flufiprole in rat liver microsomes was investigated in vitro. The result showed remarkable enantioselectivity for fipronil and ethiprole with the EF values of 0.11-0.58. The metabolite fipronil-sulfone was formed with the degradation of fipronil. R-Ethiprole to S-ethiprole transformation was observed, but not S-ethiprole to R-ethiprole. No enantioselective metabolism was observed for flufiprole with the EF values of 0.49-0.51. The enzymatic assays showed that the inhibition ratio of R-fipronil and S-ethiprole was 1.5-2.1times that of the corresponding enantiomers on CYP2E1 and CYP2D2 activity, leading to the enantioselective metabolism. The result of the homology modeling and molecular docking further revealed that S-fipronil (-7.56 kcal mol-1) and R-ethiprole (-6.45 kcal mol-1) performed better binding with CYP2E1 and CYP2D2, respectively. The results provided useful data for the risk evaluation of chiral phenylpyrazole insecticides on ecological safety and human health.

Construction of Immunomagnetic Particles with High Stability in Stringent Conditions by Site-Directed Immobilization of Multivalent Nanobodies onto Bacterial Magnetic Particles for the Environmental Detection of Tetrabromobisphenol-A.

Bacterial magnetic particles (BMPs) are an attractive carrier material for immunoassays because of their nanoscale size, dispersal ability, and membrane-bound structure. Antitetrabromobisphenol-A (TBBPA) nanobodies (Nbs) in the form of monovalence (Nb1), bivalence (Nb2), and trivalence (Nb3) were biotinylated and immobilized onto streptavidin (SA)-derivatized BMPs to construct the complexes of BMP-SA-Biotin-Nb1, -Nb2, and -Nb3, respectively. An increasing order of binding capability of BMP-SA-Biotin-Nb1, -Nb2, and -Nb3 to TBBPA was observed. These complexes showed high resilience to temperature (90 °C), methanol (100%), high pH (12), and strong ionic strength (1.37 M NaCl). A BMP-SA-Biotin-Nb3-based enzyme linked immunosorbent assay (ELISA) for TBBPA dissolved in methanol was developed, showing a half-maximum inhibition concentration (IC50) of 0.42 ng mL-1. TBBPA residues in landfill leachate, sewage, and sludge samples determined by this assay were in a range of

Oxalic Acid in Root Exudates Enhances Accumulation of Perfluorooctanoic Acid in Lettuce.

Perfluorooctanoic acid (PFOA) is bioaccumulative in crops. PFOA bioaccumulation potential varies largely among crop varieties. Root exudates are found to be associated with such variations. Concentrations of low-molecular-weight organic acids (LMWOAs) in root exudates from a PFOA-high-accumulation lettuce variety are observed significantly higher than those from PFOA-low-accumulation lettuce variety (p < 0.05). Root exudates and their LMWOAs components exert great influences on the linear sorption-desorption isotherms of PFOA in soils, thus activating PFOA and enhancing its bioavailability. Among root exudate components, oxalic acid is identified to play a key role in activating PFOA uptake, with >80% attribution. Oxalic acid at rhizospheric concentrations (0.02-0.5 mM) can effectively inhibit PFOA sorption to soils by decreasing hydrophobic force, electrostatic attraction, ligand exchange, and cation-bridge effect. Oxalic acid enhances dissolution of metallic ions, iron/aluminum oxides, and organic matters from soils and forms oxalate-metal complexes, based on nuclear magnetic resonance spectra, ultraviolet spectra, and analyses of metal ions, iron/aluminum organometallic complexes, and dissolved organic carbon. The findings not only reveal the activation process of PFOA in soils by root exudates, particularly oxalic acid at rhizospheric concentrations, but also give an insight into the mechanism of enhancing PFOA accumulation in lettuce varieties.

Effects of dibutyl phthalate contamination on physiology, phytohormone homeostasis, rhizospheric and endophytic bacterial communities of Brassica rapa var. chinensis.

Phthalates are plasticizers and are ubiquitously detected in the environment, frequently at mg/kg levels. The present study aimed to evaluate the effects of dibutyl phthalate (DBP) on germination, growth, enzyme activity, phytohormone homeostasis and bacterial communities of two cultivars of Brassica rapa var. chinensis. The germination rate was decreased up to 20% compared to the control, and the growth of the vegetables was severely inhibited at the early stage when exposed to DBP at 20 mg/kg. Antioxidant defense enzyme activities and malondialdehyde (MDA) content increased upon exposure to DBP. A dose-response of auxin (IAA) was observed after a 2 d exposure. Gibberellin (GA3) and abscisic acid (ABA) responded at day 10 under DBP stress. GA3 did not show a clear dose-response effect and ABA increased about 3 times as the DBP concentration increased from 2 to 20 mg/L. Microbial population shifts were observed, especially in rhizosphere soil and roots. No obvious change occurred for the α diversity of rhizospheric bacteria among different treatments. Chao1, Shannon and Simpson indices of the root endophytic bacteria showed a decreasing trend with increasing DBP supplementation, while all the indices increased in shoot endophytic bacteria in comparison to the control. The results indicated that exposure to DBP may compromise the fitness of the leafy vagetables and alter the endophytic and rhizospheric bacteria, which might further affect the nutrients of the vegetables and alter ecosystem functions.

Characteristics of bacterial populations in an industrial scale petrochemical wastewater treatment plant: Composition, function and their association with environmental factors.

The efficiency of petrochemical wastewater biological treatment is dependent upon complex bacterial communities. A well understanding of the structure and function of bacterial community and their association with environmental variables is essential for the elucidation of contaminant removal mechanisms and optimization of wastewater treatment processes. In this study, the bacterial communities and metabolic functions in the primary hydrolysis acidification unit (PHAU), cyclic activated sludge system (CASS), secondary hydrolysis acidification unit (SHAU), and biological aerated filter (BAF) of a petrochemical wastewater treatment plant (WWTP) were studied via Illumina high-throughput sequencing. The correlations between bacterial community and environmental variables were also investigated. The phylum Proteobacteria, Planctomycetes, Chloroflexi, Acidobacteria and Bacteroidetes were dominant in the petroleum WWTP. The bacterial communities varied with wastewater characteristics and operational parameters, as a result of the differences in biosystems functions. Phylogenetic analysis showed that the genes involved in the degradation of benzoate, nitrotoluene and aminobenzoate degradation were abundant in PHAU, and the genes related to the degradation of benzoate, aminobenzoate, chloroalkane, chloroalkene, caprolactam, naphthalene and toluene were abundant in CASS, SHAU and BAF. The Redundancy analysis (RDA) suggested that biochemical oxygen demand (BOD5), NH4+-N and total nitrogen concentrations exhibited significant impacts in shaping the structure of bacterial community. Variance partitioning analysis (VPA) showed that 18.6% of the community variance was related to wastewater characteristics, higher than operational parameters of 4.5%. These results provide insight into microbial community structure and metabolic function during petrochemical wastewater treatment, and discern the relationships between bacterial community and environmental variables, which can provide basic data and a theoretical analysis of the design and operation optimization in petrochemical WWTP.

Rice root exudates enhance desorption and bioavailability of phthalic acid esters (PAEs) in soil associating with cultivar variation in PAE accumulation.

Phthalic acid esters (PAEs) is a class of prevalent pollutants in agricultural soil, threating food safety through crop uptake and accumulation of PAEs. Accumulation of PAEs varies largely among crop species and cultivars. Nevertheless, how root exudates affect PAE bioavailability, dissipation, uptake and accumulation is still not well understood. In the present study, desorption and pot experiments were designed to investigate how root exudates from high-(Peizataifeng) and low-(Fengyousimiao) PAE accumulating rice cultivars affect soil PAE bioavailability, dissipation, and accumulation variation. Rice root exudates including low molecular weight organic acids (LMWOAs) of Peizataifeng and Fengyousimiao could enhance desorption of two typical PAE compounds, di-n-butyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP), from aged soil to their available fractions by increasing soil dissolved organic carbon (DOC), thus improving their bioavailability in soil. Peizataifeng produced twice higher amounts of oxalic acid, critic acid and malonic acid in root exudates, and exhibited stronger effects on enhancing desorption and bioavailability of DBP and DEHP than Fengyousimiao. Higher (by about 50%) total organic carbon contents of root exudates from Peizataifeng led to higher (by 10-30%) soil microbial biomass carbon and nitrogen than Fengyousimiao, and thus promoted more PAE dissipation from soil than Fengyousimiao. Nevertheless, higher (by 20-50%) soil DOC and significantly higher PAE bioavailability in the soils planted Peizataifeng resulted in greater (by 53-93%) PAE accumulation in roots and shoots of Peizataifeng than Fengyousimiao, confirming by higher (by 1.82-3.48 folds) shoot and root bioconcentration factors of Peizataifeng than Fengyousimiao. This study reveals that the difference in root exudate extent and LMWOAs between Peizataifeng and Fengyousimiao differentiates PAE accumulation.