N-TiO2/硅藻土负载型纳米材料可见光催化降解水中Microcystin-LR

以钛酸四丁酯(C16H36O4Ti)为Ti源,尿素((NH2)2CO)为N源,硅藻土(Diatomite)为载体,采用溶胶凝胶法制备硅藻土负载氮掺杂二氧化钛改性纳米材料(N-TiO2/Diatomite).利用SEM、XRD、XPS、FT-IR、UV-Vis DRS对其进行系列特性表征及可见光催化性能分析,探究Microcystin-LR初始浓度对光催化的影响,分析其降解动力学和降解途径.结果表明,硅藻土负载优化了N-TiO2分子的分散性,形成了链条型纳米孔隙球状结构;N元素掺杂、硅藻土负载不影响材料晶型,晶粒粒径减小至11.39 nm;Si、N分别与TiO2成键;光响应强度和范围红移,可见光活性显著提升.以优化制备条件(350℃煅烧、掺N的物质的量分数为8%)的改性N-TiO2/Diatomite材料可见光催化降解Microcystin-LR,当初始质量浓度为1 mg·L^-1的Microcystin-LR水溶液反应6 h后降解率可达95.0%,矿化率为83.9%;反应符合准一级动力学方程,速率常数k为0.453 3 h^-1.

微囊藻毒素Microcystin-LR体外遗传毒性

背景与目的:应用人类淋巴母细胞TK6研究微囊藻毒素(Microcystin_LR,MCLR)的体外遗传毒性。材料与方法:MCLR体外染毒TK6细胞4h或24h后检测细胞毒性、微核及tk位点突变频率。结果:4h染毒未引发明显细胞毒性,24hMCLR染毒导致TK6细胞相对存活率下降,细胞微核率及TK基因突变频率明显上升,并有剂量-反应关系。最高浓度组(80μg/ml)的细胞微核率及TK基因突变频率分别是对照组的4.8及5.1倍。MCLR诱发tk位点两种不同表型的突变细胞集落,即正常生长集落及缓慢生长集落,并以后者为主。结论:24h染毒MCLR可以诱发TK6细胞微核及基因突变,揭示MCLR可能是一种断裂剂。

Relationship Between Microcystin in Drinking Water and Colorectal Cancer

Objective To investigate the association of microcystin (MC) in drinking water with the incidence of colorectal cancer. Methods The study was designed as a retrospective cohort. Eight townships or towns were randomly selected as the study sites in Haining City of Zhejiang Province, China. 408 cases of colon and rectum carcinomas diagnosed from 1977 to 1996 in the study sites were included, and a survey on types of drinking water of these patients was conducted. Samples of different water sources (well, tap, river and pond) were collected separately and microcystin concentrations were determined by indirect competitive ELISA method. Results The incidence rate of colorectal cancer was significantly higher in population who drank river and pond water than those who drank well and tap water. Compared to well water, the relative risk (RR) for colorectal cancer was 1.88 (tap), 7.94 (river) and 7.70 (pond) respectively. The positive rate (>50 pg/mL) of microcystin in samples of well, tap, river and pond water was 0, 0, 36.23% and 17.14% respectively. The concentration of microcystin in river and pond water was significantly higher than that in well and tap water (P<0.01). Spearman rank correlation analysis showed that in the study sites, the microcystin concentration of river and pond water was positively associated with the incidence of colorectal cancer (rs= 0.881, P<0.01). Conclusions The types of drinking water are positively associated with the incidence of colorectal cancer in the study sites, and this may be related to microcystin contamination of drinking water. Further biological study is needed to support the possible causative role of mycrocystin in carcinogenesis of colon and rectum.

Seven microcystins from Microcystis waterbloom in Lake Dalai,China

Seven types of microcystins,isolated from Microcystis waterbloom in Lake Dalai, were characterized.The major toxins:MCYST-LR,MCYST-RR,[D-Asp^3]MCYST-LR and [Dha^7]MCYST-LR were identified by high performance liquid chromatography(HPLC),as com- pared with the authentic microcystins.The minor toxins:MCYST FR,[L-Mser^7]MCYST-LR and an unknown MCYST which was most likely to be MCYST-(H_4)YR were identified with frit- fast atom bombardment liquid chromatography/mass spectrometry(Frit-FAB LC/MS)and amino acid analysis.The toxigenic diversity in blue-green algae(cyanobacteria)was discussed.

磁性功能化纳米粒子对微囊藻毒素Microcystin-LR的吸附性能研究

通过水热合成的方法制备出磁性Fe3O4纳米粒子,并将其表面功能化,得到新型的磁性纳米粒子.对影响微囊藻毒素Microcystin-LR吸附效果的一些因素如吸附剂加入量、吸附时间、浓度、p H等进行了优化.研究结果表明,制得的磁性吸附剂具有良好的吸附性能,适用于水中痕量藻毒素的去除.

Hepatic Histopathological Characteristics and Antioxidant Response of Phytoplanktivorous Silver Carp Intraperitoneally Injected with Extracted Microcystins

Objective To investigate the hispathological characteristics and antioxidant responses in liver of silver carp after intraperitoneal administration of microcystins （MCs） for further understanding hepatic intoxication and antioxidation mechanism in fish. Methods Phytoplanktivorous silver carp was injected intraperitoneally （i.p.） with extracted hepatotoxic microcystins （mainly MC-RR and -LR） at a dose of 1000 μg MC-LReq./kg body weight, and liver histopathological changes and antioxidant responses were studied at 1, 3, 12, 24, and 48 h, respectively, after injection. Results The damage to liver structure and the activities of hepatic antioxidant enzymes including catalase （CAT）, superoxide dismutase （SOD）, and glutathione peroxide （GPX） were increased in a time-dependent manner. Conclusion In terms of clinical and histological signs of intoxication and LD50 （i.p.） dose of MC-LR, silver carp appears rather resistant to MCs exposure than other fishes. Also the significantly increased SOD activity in the liver of silver carp suggests a higher degree of response to MCs exposure than CAT and GPX.

Microcystin-LR对体外牛子宫内膜上皮细胞增殖和凋亡的影响

使用Microcystin-LR体外处理牛子宫内膜上皮细胞,探究其对细胞活率影响及分子调控机制,以期为提高牛繁殖效率提供理论基础和实践依据。试验运用CCK-8检测MC-LR处理后细胞存活率;流式细胞术检测细胞周期变化和细胞凋亡率;Annexin V-FITC试剂盒检测细胞凋亡;实时荧光定量检测Pi3k、Akt、mTOR、Cyt-c、Caspase-3、Caspase-9和p53基因mRNA表达量。Western blot检测Pi3k、Akt、Caspase-3和Caspase-9蛋白表达量。结果表明,不同浓度和时间处理下细胞存活率出现升高和降低两种相反情况,根据CCK-8检测结果,选择12 h,100μg·L^(-1)和24 h,160μg·L^(-1)两种处理方案开展后续试验。在12 h,100μg·L^(-1)条件下,Pi3k、Akt、mTOR的mRNA表达量升高(P<0.01),Cyt-c、Caspase-3和Caspase-9基因mRNA表达量下降(P<0.05),Pi3k和Akt蛋白表达量升高(P<0.05),Caspase-3和Caspase-9蛋白表达量降低(P<0.05)。处于G0/G1期细胞数量减少(P<0.01),处于G2/M和S期细胞数量增加(P<0.01);p53基因mRNA表达量升高(P<0.05)。在24 h,160μg·L^(-1)处理条件下,Caspase-3、Caspase-9、Bax/Bcl2基因mRNA表达量升高(P<0.05),Caspase-3和Caspase-9蛋白表达量升高(P<0.05)。研究表明,100μg·L^(-1)MC-LR处理细胞12 h,细胞通过增强Pi3k-Akt-mTOR信号通路,抑制线粒体凋亡通路促进细胞增殖,同时导致处于G1期细胞数量减少、G2/M期和S期细胞数量增加。160μg·L^(-1)MC-LR处理细胞24 h,细胞通过活化线粒体凋亡通路发生凋亡。

A method to extract algae toxin of microcystin-LR

A simple and low-cost method to obtain cyanobacterial toxin microcystin-LR(MC-LR) was developed. A new strain of Microcystis aeruginosa, named DC-1, producing microcystin-LR but not microcystin-RR, was separated from the field blooming algae samples of Dianchi Lake, in southwest of China. Following three times' freeze and thaw treatment, the cultivated DC-1 cells were extracted with 40% methanol in water. The extract was centrifuged and the supernatant applied to a Hydrophilic-Lipophilic Balance(HLB) SPE cartridge. Eluted impurities with a certain gradient from 30% to 50% methanol in water, MC-LR was finally eluted from the HLB cartridge with 60% methanol in water, and samples containing 3.85% to 14.8% of MC-LR were obtained. These MC-LR samples may be used in adsorption and biodegradation experiments instead of using expensive standard reagents.

Using the nematode Caenorhabditis elegans as a model animal for assessing the toxicity induced by microcystin-LR

Among more than 75 variants of microcystin （MC）, microcystin-LR （MC-LR） is one of the most common toxins. In this study, the feasibility of using Caenorhabditis elegans to evaluate MC-LR toxicity was studied. C. elegans was treated with MC-LR at different concentrations ranging from 0.1 to 80 μg/L. The results showed that MC-LR could reduce lifespan, delay development, lengthen generation time, decrease brood size, suppress locomotion behavior, and decreases hsp-16-2-gfp expression. The endpoints of generation time, brood size, and percentage of the population expressing hsp-16-2-gfp were very sensitive to 1.0μg/L of MC-LR, and would be more useful for the evaluation of MC-LR toxicity. Furthermore, the tissue-specific hsp-16-2-gfp expressions were investigated in MC-LR-exposed animals, and the nervous system and intestine were primarily affected by MC-LR. Therefore, the generation time, brood size, and hsp-16-2-gfp expression in C. elegans can be explored to serve as valuable endpoints for evaluating the potential toxicity from MC-LR exposure.

Microbial biodegradation of microcystin-RR by bacterium Sphingopyxis sp. USTB-05

A strain, USTB-05, isolated from Lake Dianchi, China, degraded the cyanobacterial toxin microcystin-RR （MC-RR） at the rate of 16.7 mg/L per day. Analysis of 16S rDNA sequence showed that the strain was Sphingopyxis sp. Enzymatic degradation pathways for MC-RR by Sphingopyxis sp. USTB-05 were identified. Adda-Arg peptide bond of MC-RR was cleaved and then a hydrogen and a hydroxyl were combined onto the NH2 group of Adda and the carboxyl group of arginine to form a linear molecule as intermediate product within the first few hours. Then, through dehydration reaction, two hydrogen of amino group on arginine reacted with adjacent hydroxyl on carbon to form a linear MC-RR with two small peptide rings as the final product after 24 hr. These biodegradation pathways were different from those reported for other strains, implying that MC-RR may undergo different transformations and different products were formed due to various bacteria in natural lakes and reservoirs.

Ecological damage of submerged macrophyte Myriophyllum spicatum by cell extracts from microcystin(MC)-and non-MC-producing cyanobacteria,Microcystis

To explore how decomposed Microcystis-dominant cyanobacterial blooms affect submerged macrophytes,the submerged plant Myriophyllum spicatum was exposed to cell extracts from microcystin(MC)-and non-MC-producing Microcystis strains in a laboratory experiment.Results showed that both Mcracystis cell extracts exerted obvious damages to plant biomass,photosynthesis,primary and secondary metabolism measures,and resistance of plant antioxidant systems,with MC-producing Microcystis having stronger effects due to the presence of MCs.Cyanotoxins other than MCs responsible for the negative effects from both strains needs further identification.The Shannon diversity and Chao1 indices of epiphytic and planktonic bacteria were decreased by the cell extracts from both Microcystis strains.However,epiphytic and planktonic bacterial communities responded differently to cell extracts at the genus level.The dominant genera of planktonic bacteria including Enterobacter,Pseudomonas,and Novosphingobium from phylum Proteobacteria,Chryseobacterium from phylum Bacteroidetes,and Microbacterium from Actinobacteriota in the treatments with cell extracts were previously reported to have strains with algicidal and MC-degrading capabilities.B acterial genes associated with energy production and conversion,amino acid transport and metabolism,and inorganic ion transport and metabolism,were more abundant in both treatments than the control for planktonic bacteria,but less abundant for epiphytic bacteria.We speculate that planktonic bacterial communities have the potential to use and degrade substances derived from Microcystis cell extracts,which may be beneficial for M.spicatum to alleviate damages from Microcystis.Further research is needed to verify the structure and function dynamics of epiphytic and planktonic bacteria in the interaction between cyanobacteria and submerged macrophytes.

Identification and Determination of Microcystins in Source Water and Waterbloom Sample From Meiliang Bay,Taihu Lake,China

Objective To identify and determine the congener and level of microcystins in the source water of Taihu Lake. Methods Improved method of SPE combined with HPLC was employed to detect the concentration and varieties of microcystins in source water and bloom samples collected from Meiliang Bay, Taihu Lake. Results The contents of two predominant microcystin components, MC-RR, and MC-LR, were relatively high in samples during warm months and correlated with the phase of algae growth. The maximum concentrations of MC-RR and MC-LR in water sample reached 3.09±0.53μg/L and 2.39±0.41μg/L during the period of water bloom in September 2004, respectively. Even without waterbloom, the concentration of MC-LR in source water sample was still higher than the guideline value. Conclusion The status of microcystin pollution in this region is serious and measures to monitor and control the growth of cyanobacteria are urgently needed.

Uncertainty Evaluation of Determination of Microcystin MC-LR in Environmental Samples by Solid Phase Extraction-Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry

To assess uncertainty of determination of MC-LR in environmental samples by solid phase extraction- ultra performance liquid chromatography- tandem mass spectrometry,the sources of the uncertainty were evaluated firstly,and the expanded uncertainty was calculated finally.The results show that when MC-LR concentration in the water samples was 0.50 μg/L,the expanded uncertainty was 0.00628 μg/L(k=2).

Evaluation of Size Structure in Freshwater Cyanobacterial Populations: Methods to Quantify Risk Associated with Changes in Biomass and Microcystin Concentrations

Cyanobacterial populations in surface waters, including drinking water supplies and recreational waters, represent an ever present challenge for resource managers. As communities continuously respond to external and internal processes, dynamic profiles of composition, dominance, growth and toxigenicity emerge. In this study measures of size structure and biomass, quantified using light microscopy and fluorometry, were used to estimate microcystin concentrations through linear regression analysis. Toxigenic profiles using cyanobacterial biomass were developed for lakes dominated by Microcystis spp. and Dolichospermum spp., influenced by both genus-specific pigment concentrations as well as microcystin concentrations. Community composition (Log %MIC) and biomass were used to describe microcystin concentrations in mixed assemblages, where composition was the first input variable. The accessory photopigment phycocyanin was used to describe the linear relationship between the daily growth and net microcystin production rates in the bloom-forming Microcystis spp. samples, suggesting that this size-fractionated sample may provide indications of potential toxigenicity in the whole lake water sample. Future investigations using fluorometric evaluation of cyanobacterial populations could provide additional applications and metrics for use by resource managers to quantify risk association with elevated cyanotoxin concentrations.

Accumulation of microcystins in water and economic fish in Phayao Lake, and fish ponds along the Ing River tributary in Chiang Rai, Thailand

This study determined the levels of microcystins in water and fish from Phayao Lake, Phayao Province and selected fish ponds along the Ing River tributary in Chiang Rai Province. Samples were collected monthly for 8 months (January to August 2011 for Phayao Lake, and November 2008 to June 2009 for fish ponds) and were analyzed by HPLC. The highest total microcystin-LR levels in water and fish in Phayao Lake were recorded in April 2010 at 2.60 ± 2.48 μg·L-1 and 0.20 ± 0.03 μg·kg-1 dry weight, respectively. Microcystis aeruginosa Kütz were the dominant species (271.6 ± 72.4 mm3/m3) in the lake. Colony number of Microcystis spp showed a positive correlation with soluble orthophosphate (r2 = 0.77). Similarly, Nile tilapia ponds surveyed along the tributary in Chiang Rai were contaminated with microcystins as well. The highest concentration detected in water was in March 2009 (0.58 ± 0.24 μg·L-1), whilst the maximum concentration in fish was recorded in April 2009 (2.68 ± 0.51 μg·kg-1 dry weight). Microcystis spp. dominated the pond waters and was positively correlated with chlorophyll a (r2=0.80) and soluble nitrate (r2=0.71). The highest concentration of the cyanobacteria was recorded in February 2009 at 4272.5 ± 62.3 mm3/m3. Results showed that total microcystin-LR concentration in fish in Chiang Rai ponds were higher than in Phayao Lake. This study suggested the possible health risks associated with the bioaccumulation of microcystins in fish (Nile tilapia) cultivated in fish ponds along the tributary in Chiang Rai and in Phayao Lake.

Degradation of Microcystin-RR by Combination of UV/H_2O_2 Technique

The experiments were performed to investigate the degradation of microcystins in order to assess the effectiveness and feasibility of UV/H2O2 system for the disinfection of water polluted by microcystins. The influence factors such as H2O2, pH and UV light intensities were investigated respectively. Degradation of microcystin-RR （MC-RR） could be fitted by either the pseudo-first-order or second-order rate equations. This homogenous system could significantly enhance the degradation rate due to the synergetic effect between UV and H2O2. The degradation mainly followed the mechanism of direct photolysis and .OH oxidation reactions. Experimental results showed that 94.83% of MC-RR was removed under optimal experimental conditions and the UV/H2O2 system provided an alternative to promote the removal of microcystins in drinking water supplies.

Studies on Extracting Microcystin-Lr from Microcystis Aeruginosa by Water Bath

Different temperatures of water bath was used to extract the intracellular microcystin-LR(MC-LR) of Microcystis aeruginosa. Researching the extraction efficiency under the suitable temperature, so that it could find out the best temperature and time for extracting MC-LR from Microcystis aeruginosa cells. Five equal Microcystis aeruginosa was used to find out the best temperature, extracting at 60℃, 70℃, 80℃, 90℃ and 100℃ for 15 minutes, respectively. Results showed that the content of MC-LR extracted with the water under 100℃ was the highest. But meanwhile, the type and the content of impurities was the highest, too. In addition, another six equal Microcystis aeruginosa was extract with the water under 100℃ for 5min, 10 min, 15 min, 20 min, 25 min and 30 min respectively. It was proved that 20 minutes was enough for extracting MC-LR from Microcystis aeruginosa, no long time was needed.

佛波脂及Microcystine-LR对sHRsp内脏阻力血管平滑肌钙通道的影响

目的研究佛波脂(phorbol 12-myristate 13-acetate,PMA)及microcys-tine-LR(MCYST-LR)对卒中易感型自发性高血压大鼠(SHRsp)及常压对照Wistar大鼠肠系膜动脉A4-A5段分支阻力血管平滑肌电压依赖性钙通道的影响。方法采用膜片箝全细胞钡电流方式记录钙通道的活动。结果佛波脂激活蛋白激酶C(PKC)或MCYST-LR抑制细胞蛋白磷酸酶(PPⅠA、PPⅡA)而相对增加磷酸化过程,均可激活内脏阻力血管平滑肌电压依赖性钙通道。结论 PMA的激活效应,在SHRsp,是使开放的L型钙通道活动显著增强,T型钙通道活动略有增加;而在Wistar大鼠,则以T型钙电流增加为主。MCYST-LR仅使SHRsp的L型钙通道活动显著增强。提示在分析高血压的外周阻力增高机制时,应进一步分析PKC和磷酸化机制对钙通道各电流成分的影响。

Photocatalytic Treatment of Microcystin-LR-Containing Wastewater Using Pt/WO ₃Nanoparticles under Simulated Solar Light

This study investigates the photocatalytic degradation of microcystin-LR (MC-LR) under simulated solar light using Pt modified nano-sized tungsten trioxides (Pt/WO3). Photocatalytic activity was higher during the degradation of MC-LR with Pt/WO 3 than with pure WO 3 or Ti O2 . The catalyst loading greatly affect the degradation performance. The rate of degradation is influenced by the initial pH of the reaction solution. This study also investigates the photocatalytic inactivation of cyanobacteria. The results show that the algal growth was successfully controlled by the Pt/W O 3 . This study suggests Pt/W O 3 photocatalytic oxidation with solar light is a promising treatment for water containing MC-LR.

The combined effects of Dolichospermum flos-aquae, light, and temperature on microcystin production by Microcystis aeruginosa

The effects of light, temperature, and coculture on the intracellular microcystin-LR(MCLR) quota of M icrocystis aeruginosa were evaluated based on coculture experiments with nontoxic Dolichospermum( Anabaena) fl os- aquae. The MC-LR quota and transcription of m cy B and m cy D genes encoding MC synthetases in M. aeruginosa were evaluated on the basis of cell counts, high-performance liquid chromatography, and reverse-transcription quantitative real-time PCR. The MC-LR quotas of M. aeruginosa in coculture with a 1/1 ratio of inoculum of the two species were signifi cantly lower relative to monocultures 6-d after inoculation. Decreased MC-LR quotas under coculture conditions were enhanced by increasing the D. fl os- aquae to M. aeruginosa ratio in the inoculum and by environmental factors, such as temperature and light intensity. Moreover, the transcriptional concentrations of mcy B and mcy D genes in M. aeruginosa were signifi cantly inhibited by D. fl os- aquae competition in coculture(P <0.01), lowered to 20% of initial concentrations within 8 days. These data suggested that coculture effects by D. fl os- aquae not only reduced M. aeruginosa 's intracellular MC-LR quota via inhibition of genes encoding MC synthetases, but also that this effect was regulated by environmental factors, including temperature and light intensities.