Shupei Cheng

Metagenomic insights into chlorination effects on microbial antibiotic resistance in drinking water

This study aimed to investigate the chlorination effects on microbial antibiotic resistance in a drinking water treatment plant. Biochemical identification, 16S rRNA gene cloning and metagenomic analysis consistently indicated that Proteobacteria were the main antibiotic resistant bacteria (ARB) dominating in the drinking water and chlorine disinfection greatly affected microbial community structure. After chlorination, higher proportion of the surviving bacteria was resistant to chloramphenicol, trimethoprim and cephalothin. Quantitative real-time PCRs revealed that sulI had the highest abundance among the antibiotic resistance genes (ARGs) detected in the drinking water, followed by tetA and tetG. Chlorination caused enrichment of ampC, aphA2, bla(TEM-1), tetA, tetG, ermA and ermB, but sulI was considerably removed (p < 0.05). Metagenomic analysis confirmed that drinking water chlorination could concentrate various ARGs, as well as of plasmids, insertion sequences and integrons involved in horizontal transfer of the ARGs. Water pipeline transportation tended to reduce the abundance of most ARGs, but various ARB and ARGs were still present in the tap water, which deserves more public health concerns. The results highlighted prevalence of ARB and ARGs in chlorinated drinking water and this study might be technologically useful for detecting the ARGs in water environments.

Health risk assessment of polycyclic aromatic hydrocarbons in the source water and drinking water of China: Quantitative analysis based on published monitoring data

A carcinogenic risk assessment of polycyclic aromatic hydrocarbons (PAHs) in source water and drinking water of China was conducted using probabilistic techniques from a national perspective. The published monitoring data of PAHs were gathered and converted into BaP equivalent (BaP(eq)) concentrations. Based on the transformed data, comprehensive risk assessment was performed by considering different age groups and exposure pathways. Monte Carlo simulation and sensitivity analysis were applied to quantify uncertainties of risk estimation. The risk analysis indicated that, the risk values for children and teens were lower than the accepted value (1.00E-05), indicating no significant carcinogenic risk. The probability of risk values above 1.00E-05 was 5.8% and 6.7% for adults and lifetime groups, respectively. Overall, carcinogenic risks of PAHs in source water and drinking water of China were mostly accepted. However, specific regions, such as Yellow river of Lanzhou reach and Qiantang river should be paid more attention. Notwithstanding the uncertainties inherent in the risk assessment, this study is the first attempt to provide information on carcinogenic risk of PAHs in source water and drinking water of China, and might be useful for potential strategies of carcinogenic risk management and reduction.

Health risk from exposure of organic pollutants through drinking water consumption in Nanjing, China.

Human health risk analysis for 24 organic pollutants in drinking water of Nanjing was conducted. For non-carcinogenic risk, the 95th percentile hazard quotient (HQ) values of pollutants were all less than the unacceptable level of one. Considering the lifetime carcinogenic risk (LCR), however, the 95th percentile LCR values of 2,6-dinitrotoluene (1.30E-05), benzo(b)fluoranthene (3.10E-05), benzo(a)pyrene (3.37E-05) and dibenz(a,h)anthracene (2.09E-05) exceeded the unacceptable level of 1.00 E-05. These results suggest that organic pollutants in drinking water of Nanjing might pose potential lifetime carcinogenic risk for local consumers, and concerted efforts are required to ensure safety of consumers.

Multivariate statistical study of organic pollutants in Nanjing reach of Yangtze River.

Multivariate statistical approach was used to identify the source apportionment of 25 semi-volatile compounds (SVOCs) in surface water in Nanjing reach of Yangtze River, China. Surface water samples were collected from six sites in January 2007. Concentrations of SVOCs were determined by gas chromatography equipped with a mass spectrometry detector (GC-MS). Cluster analysis (CA) and principal component analysis-multiple linear regression (PCA-MLR) were used for evaluation of contamination status, distribution and source apportionment. The results of CA showed that the six sites in this study could be divided into two significant groups, i.e. low and high pollutant groups. PCA-MLR results suggested that four source types were identified, explaining about 84.5% of the total variance. Of four sources, industrial and domestic sewage sources contributed 43.5-64.8% of various SVOCs in six sites, precipitance and runoff sources 4.22-42.87%, shipping sources 4.22-23.49%, and other miscellaneous sources 1.05-8.97%. These results indicated that point source pollutants affected the water quality of this region. High correlation coefficient (R(2)=0.973) between the measured and predicted concentrations of SVOCs suggested the applicability of the PCA-MLR for estimation of source contribution to the SVOCs in water.

Responses of mouse liver to dechlorane plus exposure by integrative transcriptomic and metabonomic studies.

Dechlorane plus (DP), a chlorinated flame retardant, has been widely detected in different environmental matrices and biota. However, toxicity data for DP have seldom been reported. In the present study, we investigated hepatic oxidative stress, DNA damage, and transcriptomic and metabonomic responses of male mice administered 500 mg/kg, 2000 mg/kg, and 5000 mg/kg of DP by gavage for 10 days. The results showed that DP exposure increased the level of superoxide dismutase (SOD) and 8-hydroxy-2-deoxyguanosine (8-OHdG). The microarray-based transcriptomic results demonstrated that DP exposure led to significant alteration of gene expression involved in carbohydrate, lipid, nucleotide, and energy metabolism, as well as signal transduction processes. The NMR-based metabonomic analyses corroborated these results showing changes of metabolites associated with the above altered mechanisms. Our results demonstrate that an oral exposure to DP can induce hepatic oxidative damage and perturbations of metabolism and signal transduction. These observations provide novel insight into toxicological effects and mechanisms of action of DP at the transcriptomic and metabonomic levels.

A Comparative Analysis of Environmental Quality Assessment Methods for Heavy Metal-Contaminated Soils

Abstract Four assessment methods (two pollution indexes and two fuzzy mathematical models) were employed to investigate the environmental quality of four soils around a ferroalloy plant in Nanjing City. Environmental quality was assessed as class IV (moderately polluted) for each soil with single-factor index method, and was identifled to be classes IV, III (slightly polluted), III, and III for soils A, B, C, and D, respectively, with the comprehensive index model. In comparison with the single-factor index method, the comprehensive index model concerned both dominant parameter and average contribution of all factors to the integrated environmental quality. Using the two fuzzy mathematical methods (single-factor deciding and weighted average models), the environmental risks were determined to be classes IV, III, II (clean), and II for soils A, B, C, and D, respectively. However, divergence of the membership degree to each pollution class still occurred between the two methods. In fuzzy mathematical methods, membership functions were used to describe the limits between difierent pollution degrees, and difierent weights were allocated for the factors according to pollution contribution. Introduction of membership degree and weight of each factor to fuzzy mathematical models made the methods more reasonable in the fleld of environmental risk assessment.

Occurrence, abundance and elimination of class 1 integrons in one municipal sewage treatment plant

Integrons are elements that encode a site-specific recombination system that recognizes and captures mobile gene cassettes and are closely related to multiple resistances of environmental microorganisms. This study was undertaken to determine the efficiency of an activated sludge process to remove integrons. The prevalence and characteristics of class 1 integrons were investigated for bacterial species isolated from the activated sludge of Nanjing Jiangxinzhou sewage treatment plant (STP, China). A total of 189 bacterial strains were isolated from influent water, activated sludge and effluent water, and PCR–RFLP (Polymerase chain reaction—restriction fragment length polymorphism) of 16S rRNA gene showed that the isolated bacteria were Escherichia coli, Aeromonas veronii, Klebsiella spp., Aeromonas salmonicida and Aeromonas media. PCRs showed that 57 isolates contained class 1 integronase gene intI1. The integron detection frequency in the isolated strains was 20.4% for influent, 30.9% for activated sludge and 38.9% for effluent. Quantitative real-time PCR assay showed that the abundance of integrons in effluent was higher than that in influent. This study indicates that class 1 integrons are wide-spread in STPs which might be involved in multiple resistances in the activated sludge characterized by high biomass and biodiversity.

Microcystin-LR Promotes Melanoma Cell Invasion and Enhances Matrix Metalloproteinase-2/-9 Expression Mediated by NF-κB Activation

This study aimed to explore the molecular mechanisms behind the stimulation effects of microcystin-LR (a well-known cyanobacterial toxin produced in eutrophic lakes or reservoirs) on cancer cell invasion and matrix metalloproteinases (MMPs) expression. Boyden chamber assay showed that microcystin-LR exposure (>12.5 nM) evidently enhanced the invasion ability of the melanoma cells (MDA-MB-435). Tumor Metastasis PCR Array demonstrated that 24 h microcystin-LR treatment (25 nM) caused overexpression of eight genes involved in tumor metastasis, including MMP-2, MMP-9, and MMP-13. Quantitative real-time PCR, Western blotting and gelatin zymography consistently demonstrated that mRNA and protein levels of MMP-2/-9 were increased in the cells after microcystin-LR exposure (P < 0.05 each). Immunofluorescence assay and electrophoretic mobility shift assay revealed that microcystin-LR could activate nuclear factor kappaB (NF-κB) by accelerating NF-κB translocation into the nucleus and enhancing NF-κB binding ability. Furthermore, addition of NF-κB inhibitor in culture medium could suppress the invasiveness enhancement and MMP-2/-9 overexpression. This study indicates that microcystin-LR can act as a NF-κB activator to promote MMP-2/-9 expression and melanoma cell invasion, which deserves more environmental health concerns.

Toxicity of purified terephthalic acid manufacturing wastewater on reproductive system of male mice (Mus musculus)

Reproductive toxicity of purified terephthalic acid (PTA) manufacturing wastewater on the male mice (Mus musculus) was investigated after 35-day intragastric perfusion treatment with the wastewater. Fluorescein diacetate and propidium iodide staining, and flow cytometry were used to assess the toxicity of PTA wastewater on spermatogenic cells. PTA wastewater induced significant variations in the relative percentages of immature haploid, diploid, tetraploid and S-phase spermatogonia. Percentage of viable spermatogenic cells was reduced from 93.1+/-2.3 in control group to 90.4+/-1.9 in the wastewater-treated group. Testicular histopathology revealed expansion of interstitial space and reduction in the number and size of Leydig cells induced by the wastewater, which was further certified by the decrease (10.6%) in relative testes weight and the increase (101.3%) in sperm shape abnormality in the wastewater-treated group. In this study, PTA wastewater was found to have reproductive toxicity on male mice, and public health problems may potentially arise from the discharge of the wastewater into the environment.

Identifying Health Effects of Exposure to Trichloroacetamide Using Transcriptomics and Metabonomics in Mice (Mus musculus)

Microarray-based transcriptomics and one-dimensional proton nuclear magnetic resonance ((1)H NMR) based metabonomics approaches were employed to investigate the health effects of nitrogenous disinfection byproducts (N-DBPs) of trichloroacetamide (TCAcAm) on mice. Mice were exposed to TCAcAm at concentrations of 50, 500, and 5000 μg/L for 90 days, and hepatic transcriptome and serum metabonome and histopathological parameters were detected in comparison with those of control. TCAcAm esposures resulted in liver inflammation, weight loss (in 5000 ug/L TCAcAm group), and alterations in hepatic transcriptome and serum metabonome. Based on the differentially expressed genes and altered metabolites, several significant pathways were identified, which are associated with lipid, xenobiotics, amino acid and energy metabolism, and cell process. Moreover, integrative pathway analyses revealed that TCAcAm exposure in this study induced hepatotoxicity and cytotoxicity. These results also highlight the noninvasive prospect of transcriptomic and metabonomic approaches in evaluating the health risk of emerging N-DBPs.