Euglena gracilis as a model for the study of Cu2+ and Zn2+ toxicity and accumulation in eukaryotic cells

We have observed the effect of copper and zinc on the biology of Euglena gracilis. The cells displayed different sensitivities to these metals, as the apparent LC50 for Cu2+ was 0.22 mM, and for Zn2+ it was 0.88 mM. While Zn2+ was able to increase cell proliferation even at 0.1 mM, the minimal CuCl2 concentration tested (0.02 mM) was sufficient to impair cell division. Higher concentrations of these metals not only inhibited cell division in a concentration-dependent manner, but also interfered with the metabolism of E. gracilis. A higher accumulation of proteins and lipids per cell was observed at the DI50 concentration for metal-treated cells. These results suggest that the test concentration of both metals leads to a failure in completing cell division. Ultrastructural analysis indicated a chloroplast disorganization in copper-treated cells, as well as the presence of electron dense granules with different shapes and sizes inside vacuoles. Microanalysis of these granules indicated an accumulation of copper, thus suggesting a detoxification role played by the vacuoles. These results indicate that E. gracilis is an efficient biological model for the study of metal poisoning in eukaryotic cells. They also indicate that copper and zinc (copper being more poisonous) had an overall toxic effect on E. gracilis and that part of the effect can be ascribed to defects in the structure of chloroplast membranes.     

满江红干体对锌离子的生物吸附

以满江红干体为生物吸附剂,研究了不同条件下对废水中Zn²⁺的净化作用。结果表明,满江红干体对Zn²⁺的吸附是一个快速的过程,前5 min的吸附量达到最大吸附量的62.9%,30 min达到吸附平衡;初始pH值对Zn²⁺的吸附有显著的影响,最适pH值为6;随着干体量的增加,吸附率逐渐提高而吸附量则降低;随着Zn²⁺初始浓度的增加,吸附率逐渐降低而吸附量则提高。满江红干体对Zn²⁺的吸附符合Langmuir吸附等温线方程,最大吸附容量达57.5 mg/g。5次吸附解吸循环实验数据表明,重复次数和再生处理对满江红干体的吸附能力没有产生显著影响。因此,满江红干体在处理含Zn²⁺废水中的重复使用是可行的。     

Effect of humic acids on physicochemical property and Cd(II) sorption of multiwalled carbon nanotubes

Zinc pyrithione is used as an antifouling agent. However, the environmental impacts of zinc pyrithione have recently been of concern. Zinc induces diverse actions during oxidative stress; therefore, we examined the effect of zinc pyrithione on rat thymocytes suffering from oxidative stress using appropriate fluorescent probes. The cytotoxicity of zinc pyrithione was not observed when the cells were incubated with 3 μM zinc pyrithione for 3 h. However, zinc pyrithione at nanomolar concentrations (10 nM or more) significantly increased the lethality of cells suffering from oxidative stress induced by 3 mM H₂O₂. The application of zinc pyrithione alone at nanomolar concentrations increased intracellular Zn²⁺ level and the cellular content of superoxide anions, and decreased the cellular content of nonprotein thiols. The simultaneous application of nanomolar zinc pyrithione and micromolar H₂O₂ synergistically increased the intracellular Zn²⁺ level. Therefore, zinc pyrithione at nanomolar concentrations may exert severe cytotoxic action on cells simultaneously exposed to chemicals that induce oxidative stress. If so, zinc pyrithione leaked from antifouling materials into surrounding environments would be a risk factor for aquatic ecosystems. Alternatively, zinc pyrithione under conditions of oxidative stress may become more potent antifouling ingredient.     

Cornmeal-induced resistance to ciprofloxacin and erythromycin in enterococci

Triclosan is used as an antibacterial agent in household items and personal care products. Since this compound is found in maternal milk of humans and bodies of wild animals, there is growing concern among some consumer groups and scientific community that triclosan is adverse for humans and wild animals. In order to estimate adverse actions of triclosan, the effects of triclosan on intracellular Zn²⁺ concentration and cellular thiol content were studied in rat thymocytes by the use of flow cytometer with appropriate fluorescent probes. Triclosan at 1-3 μM (sublethal concentrations) increased the intensity of FluoZin-3 fluorescence (intracellular Zn²⁺ concentration) and decreased the intensity of 5-chloromethylfluorescein (5-CMF) fluorescence (cellular thiol content). Negative correlation (r = −0.985) between triclosan-induced changes in FluoZin-3 and 5-CMF fluorescences was found. Removal of external Zn²⁺ did not significantly affect the triclosan-induced augmentation of FluoZin-3 fluorescence, suggesting an intracellular Zn²⁺ release by triclosan. These actions of triclosan were similar to those of H₂O₂ and triclosan significantly potentiated the cytotoxicity of H₂O₂. Therefore, the results may suggest that triclosan at sublethal concentrations induces oxidative stress that decreases cellular thiol content, resulting in an increase in intracellular Zn²⁺ concentration by Zn²⁺ release from intracellular store(s). Since recent studies show many physiological roles of intracellular Zn²⁺ in cellular functions, the triclosan-induced disturbance of cellular Zn²⁺ homeostasis may induce adverse actions on the cells.     

Synergistic increase in cell lethality by dieldrin and H2O2 in rat thymocytes: Effect of dieldrin on the cells exposed to oxidative stress

Dieldrin, one of persistent pesticides, is highly resistant to biotic and abiotic degradation. It is accumulated in organisms. Recent studies suggest that dieldrin exerts a potent cytotoxic action on cells exposed to oxidative stress. In this study, the effect of dieldrin on rat thymocytes exposed to hydrogen peroxide (H₂O₂)-induced oxidative stress was examined. Dieldrin at 5 μM and H₂O₂ at 300 μM slightly increased cell lethality from a control value of 5.4 ± 0.5% (mean ± standard deviation of four experiments) to 7.8 ± 1.3% and 9.0 ± 0.3%, respectively. Simultaneous application of dieldrin and H₂O₂ significantly increased cell lethality to 46.2 ± 1.8%. The synergistic increase in cell lethality was dependent on dieldrin concentration (0.3–5 μM) but not on H₂O₂ concentration (30–300 μM). Dieldrin accelerated H₂O₂-induced cell death, which was estimated with the help of annexin V-FITC and propidium iodide. Presence of either dieldrin or H₂O₂ decreased the cellular content of nonprotein thiol and increased intracellular Zn²⁺ concentration. The combination of dieldrin and H₂O₂ further pronounced these effects. TPEN, a chelator of intracellular Zn²⁺, significantly attenuated the synergistic increase in cell lethality induced by dieldrin and H₂O₂. It is, therefore, suggested that dieldrin augments the cytotoxicity of H₂O₂ in a Zn²⁺-dependent manner.     

固定化小球藻与活性污泥的共生系统处理含锌废水

研究固定化小球藻与活性污泥的共生系统对含锌废水中Zn2+的去除效果,分析菌藻状态、初始Zn2+浓度、pH、固定化菌藻小球投加量和菌藻体积比等5个因素对固定化菌藻共生系统去除Zn2+的影响。结果表明,固定化活性污泥、固定化小球藻和固定化菌藻对Zn2+的去除效果均优于悬浮小球藻,其中固定化菌藻对Zn2+的去除效果最好;废水中初始Zn2+浓度小于100 mg/L时,固定化菌藻系统对废水中Zn2+的去除率达到90.5%;固定化菌藻系统去除废水中Zn2+的最佳条件是:初始Zn2+浓度为80 mg/L,pH=7,固定化小球投加量为80 mL,菌藻体积比为1∶2。     

十溴联苯醚共存条件下水中Zn(Ⅱ)的生物吸附

研究了十溴联苯醚(BDE-209)共存条件下嗜麦芽窄食单胞菌对水中Zn2+的吸附特性,并通过对菌体进行失活处理、红外光谱和X-光电子能谱分析,探讨了吸附机理。结果表明,Zn2+的吸附符合Freundlich吸附模式;嗜麦芽窄食单胞菌对Zn2+吸附作用明显,2.5 g/L菌体在2 h时,对初始浓度为2.0 mg/L Zn2+的去除率达92%。BDE-209对菌体吸附Zn2+有一定的抑制作用。各因素对嗜麦芽窄食单胞菌吸附Zn2+的影响程度由大到小依次为:投菌量>pH>BDE-209浓度。菌体对Zn2+的吸附除表面吸附外,还存在跨细胞壁细胞膜的主动运输和积累等作用。菌体中的酰胺基与羟基均参与了Zn2+吸附,而且菌体表面Ca2+与Zn2+发生了离子交换,吸附后Zn2+的价态不变。     

液/固体系中硅藻土对Pb2+和Cd2+的吸附机制

为了提高硅藻土在重金属废水处理上的应用水平,采用静态吸附实验考察了液/固体系中硅藻土对Pb2＋、Cd2＋的吸附影响因素、吸附等温线和吸附动力学属性。结果表明,随着投加量的减少,离子初始浓度的提高,pH值的增大,吸附作用时间的延长,硅藻土对Pb2＋、Cd2＋吸附量不断上升;硅藻土对Pb2＋、Cd2＋的等温吸附都符合Langmuir模型,硅藻土对Pb2＋、Cd2＋最大吸附量分别为10.428 mg/g和7.916 mg/g,硅藻土对Pb2＋具有更好的吸附能力;Pb2＋具有较低的水合自由能,更容易脱去水膜与硅藻土孔道内的活性基团发生吸附作用;双常数扩散方程可以很好地描述硅藻土对Pb2＋、Cd2＋的吸附动力学属性,硅藻土对Cd2＋有较快的吸附速率。     

US/Zn~0体系降解水中的对硝基苯甲酸

为高效去除水体中的对硝基苯甲酸、开发新型水处理技术,提出以超声与单质锌联用降解水中的对硝基苯甲酸。考察了锌投加量、溶液初始pH、声功率及溶液初始浓度对拟一级反应速率常数(k0US/Zn)的影响,比较了US、Zn0和US/Zn03体系下的降解常数,并对US/Zn0体系的降解机理进行了初探。结果表明,以上4种因素对k0US/Zn均有很大影响,k0US/Zn分别在溶液初始pH为5、声功率为120 W、溶液初始浓度为0.04 mmol/L时达到最大值,且随着锌投加量的增加而增加。超声与单质锌在降解对硝基苯甲酸的过程中存在很好的协同作用,在最优条件下,k0US/Zn=0.052 min-1,分别是单独超声降解及单独锌降解的21.5倍和2.53倍。在联用体系中,主要是依靠OH·氧化及单质锌还原的相互加强来去除对硝基苯甲酸。     

Chronic copper exposure and fatty acid composition of the amphipod Dikerogammarus villosus: results from a field study

Field study allows assessment of long-term effects on fatty acid (FA) composition of organisms under chronic exposure to metals. One expected effect of copper is peroxidation of lipids and essentially polyunsaturated fatty acids (PUFA). FA analysis was established for the amphipod Dikerogammarus villosus subjected to different degrees of copper exposure (4–40 μg Cu L⁻¹). A previous study in our team showed that this species regulates its body Cu concentration (106–135 mg Cu kg⁻¹ dry weight). Despite the high capacity of bioaccumulation, the absence of a correlation between copper concentration in D. villosus and water prevents its use as bioindicator of copper pollution. Both sexes from the most polluted site showed the lowest total FA content, but the highest PUFA percent, mainly of the long-chained variety (C20–C22). Mechanisms leading to the prevention of lipid peroxidation in this species were discussed (metallothioneins and intracellular granules) and proposed with support from literature data.     

胺基树脂的合成及对水中重金属离子的吸附特征

研究了使用氯甲基化聚苯乙烯交联微球为前驱体与二乙烯三胺经回流反应合成胺基树脂及其对水中Cd2+和Ni2+的吸附特征。结果表明,胺基官能团成功地嫁接到树脂表面,胺基含量为5.6 mmol/g。胺基树脂对Cd2+和Ni2+的吸附等温线表明,温度的升高有利于吸附,且吸附等温线都符合Langmuir模型。pH值对吸附的影响较大,最佳吸附pH值范围为4~6。2种金属离子在胺基树脂上的吸附都符合准二级动力学方程。     

Embryo toxicity of pesticides and heavy metals to the ramshorn snail, Marisa cornuarietis (Prosobranchia)

An invertebrate embryo toxicity test with the ampullariid snail, Marisa cornuarietis, to assess the toxicity of pesticides and heavy metals recently was established. Snail embryos were treated with atrazine (100, 1000, 10 000, and 30 000 μg/L), imidacloprid (10 000, 25 000, and 50 000 μg/L), Ni²⁺ (0.1, 1, 10, and 100 μg/L) or Zn²⁺ (100, 200, 500, 1000, 2000, and 5000 μg/L). The effect of these substances was examined by monitoring the following endpoints: mortality, formation of tentacles and eyes, heart rate, hatching, and weight after hatching. Effects in term of a significant delay on the formation of both tentacles and eyes were found after treatment with 100 μg/L Ni²⁺ or 200 μg/L Zn²⁺. The heart rate was shown to significantly decrease at 25 000 μg/L imidacloprid or 1000 μg/L Zn²⁺. At 100 μg/L atrazine, 10 μg/L Ni²⁺, or 1000 μg/L Zn²⁺ a significant delay in hatching became visible. No significant mortality was observed for the tested concentrations of atrazine, imidacloprid, or Ni²⁺, while 5000 μg/L Zn²⁺ resulted in 100% mortality after 10 d. The weight of freshly hatched individuals remained unaffected in all treatments. On the basis of the lowest observed effect concentrations (LOECs) recorded, we could show the M. cornuarietis embryo toxicity test (MariETT) to react up to three orders of magnitude more sensitive (for metals) and at least one order of magnitude more sensitive (for the tested organics) than the established Danio rerio embryo test.     

Characterization of bacterial communities at heavy-metal-contaminated sites

The microbial community in soil samples from two long-term contaminated sites was characterized by using culture-dependent and culture-independent methods. The two sites investigated contained high amounts of heavy metals and were located in the upper Silesia Industrial Region in southern Poland. The evaluation of the aerobic soil microbial population clearly demonstrated the presence of considerable numbers of viable, culturable bacteria at both sites. A high fraction of the bacterial population was able to grow in the presence of high amounts of metals, i.e. up to 10 mM Zn²⁺, 3 mM Pb²⁺ or 1 mM Cu²⁺. Site 1 contained significantly (P < 0.05) lower bacterial numbers growing in the presence of 10 mM Zn²⁺ than site 2, while the opposite was observed for bacteria tolerating 1 mM Cu²⁺. This coincided with the contents of these two metals at the two sites. Ecophysiological (EP) indices for copiotrophs (r-strategists) and oligotrophs (K-strategists) pointed to high bacterial diversity at both sites. Fluorescence in situ hybridization (FISH) analysis indicated that Actinobacteria and Proteobacteria represent the physiologically active fraction of bacteria at the two sites. Shannon diversity (H′) indices for FISH-detected bacterial phylogenetic groups were not significantly different at the two sites.     

粉煤灰沸石负载Ce3+/TiO2光催化降解水中的菲和荧蒽

以钛酸四丁酯为前驱体,粉煤灰合成沸石为载体,采用溶胶-凝胶方法,在低温条件下制备了稀土铈掺杂的TiO₂光催化剂。利用SEM-EDS、XRD、FTIR对催化剂进行了分析和表征。以高压汞灯为灯源,对多环芳烃菲、荧蒽的降解进行了研究。实验考查了稀土铈掺杂质量分数、催化剂用量、溶液pH、目标物初始质量浓度等因素对光催化降解的影响,研究了其光降解动力学。结果表明,当稀土铈含量为0.5%,催化剂用量为3 g/L,pH偏碱性时,催化效果最佳。光催化反应符合Langmuir-Hinshelwood 动力学规律,菲、荧蒽的降解过程符合一级反应动力学,反应速率常数分别为0.0126 min^-1,0.0099 min^-1。     

改性花生壳对Cd(Ⅱ)和Pb(Ⅱ)的吸附机理

以前期制得改性块状花生壳为对象,测定改性花生壳等电点,考察离子强度对改性花生壳吸附Cd2+和Pb2+的影响、吸附前后吸附质溶液pH变化情况及蒸馏水、NaCl、HNO3、柠檬酸和EDTA 5种解吸液对Cd2+和Pb2+的解吸效果,并通过X-射线光电子能谱仪和傅里叶变换红外光谱仪对吸附前后的改性花生壳进行表征,推测并证实了改性花生壳对Cd2+和Pb2+可能的吸附机理。结果表明,改性花生壳对Cd2+和Pb2+可能的吸附机理是:Cd2+是通过外层络合、离子交换和内层络合的联合作用被吸附的;Pb2+主要是与改性花生壳上的O、N等活性基团发生内层络合;此外,改性花生壳表面生成的二氧化锰对Cd2+和Pb2+的吸附也起到一定的作用。     

活性污泥法处理高钙废水中污泥特性的变化

通过单级SBR法处理模拟高钙废水,研究了活性污泥法处理高钙废水的过程中钙离子对COD,MLVSS,MLSS,SVI,污泥增长速率,污泥形态结构及生物相的影响,揭示活性污泥法处理高钙废水的过程中污泥量巨大的原因。采用逐步增加钙离子浓度的方法,检测到在污泥培养期([Ca2+]=0 mg/L),COD去除率为98.1%,MLVSS和MLSS稳定在4 900~5 500mg/L,污泥增长速率为67 mg/(L·d),SVI为55~60 mL/g;在驯化处理期([Ca2+]=120~2 400 mg/L),COD去除率降至87.37%,MLVSS降至2 500 mg/L,MLSS增加至19 300 mg/L,污泥增长速率为212.31 mg/(L·d),SVI降至25 mL/g;在冲击期([Ca2+]=4 000 mg/L),COD去除率降至69.23%,MLVSS降至1 600 mg/L,MLSS迅速增加至24 200 mg/L,污泥增长速率为816.67 mg/(L·d),SVI降至14 mL/g。经显微镜观察发现,污泥絮体由松散变得密实,生物相由钟虫等指示性微生物变为不适应环境的胞囊结构。结果表明,随Ca2+浓度的增加,COD去除率下降,MLSS迅速增加,MLVSS和SVI急剧缩小,说明活性污泥中的活性微生物逐渐减少,而无机物组分逐渐增多;钙离子的加入促使系统碳酸平衡向右移动,使离子状态的钙大部分转化为难降解的碳酸盐,并附着于污泥絮体上,污泥绒粒被压缩,使污泥颗粒密实度及MLSS迅速增加,导致污泥排放量巨大。     

改性污泥活性炭对水中镉离子的吸附性能

以城市污水处理厂的剩余污泥为原料,氯化锌为活化剂制备污泥活性炭,对一部分污泥活性炭用6.0 mol/L的硝酸进行改性,并研究了未改性和改性的污泥活性炭对Cd2＋的吸附行为的影响。结果表明,在pH为5.0、Cd2＋初始浓度为100 mg/L、吸附剂投加量为2.0 g/L、反应温度为25℃时,未改性的污泥活性炭吸附容量为8.45 mg/g,硝酸改性的污泥活性炭吸附容量达到了23.35 mg/g。改性和未改性的污泥活性炭对Cd2＋都有较好的吸附容量,硝酸改性大幅度提高了污泥活性炭对Cd2＋的吸附性能。常温下改性污泥活性炭对Cd2＋的吸附符合Langmuir吸附等温式。     

Enhanced resistance of yeast mutants deficient in low-affinity iron and zinc transporters to stannous-induced toxicity

Tin or stannous (Sn²⁺) compounds are used as catalysts, stabilizers in plastic industries, wood preservatives, agricultural biocides and nuclear medicine. In order to verify the Sn²⁺ up-take and toxicity in yeast cells we utilized a multi-elemental analysis known as particle-induced X-ray emission (PIXE) along with cell survival assays and quantitative real-time PCR. The detection of Sn²⁺ by PIXE was possible only in yeast cells in stationary phase of growth (STAT cells) that survive at 25 mM Sn²⁺ concentration. Yeast cells in exponential phase of growth (LOG cells) tolerate only micro-molar Sn²⁺ concentrations that result in intracellular concentration below of the method detection limit. Our PIXE analysis showed that STAT XV185-14c yeast cells demonstrate a significant loss of intracellular elements such as Mg, Zn, S, Fe and an increase in P levels after 1 h exposure to SnCl₂. The survival assay showed enhanced tolerance of LOG yeast cells lacking the low-affinity iron and zinc transporters to stannous treatment, suggesting the possible involvement in Sn²⁺ uptake. Moreover, our qRT-PCR data showed that Sn²⁺ treatment could generate reactive oxygen species as it induces activation of many stress-response genes, including SOD1, YAP1, and APN1.     

钙对李氏禾富集和耐受铬的调控作用

通过水培实验,研究钙对铬胁迫下李氏禾幼苗生理生化、草酸分泌及铬吸收量的影响,考察钙对李氏禾体内草酸合成的调控,进而促进李氏禾的铬耐性富集能力的作用。结果显示,不同浓度Cr³⁺胁迫下缺钙处理,李氏禾生长受抑制及质膜过氧化作用加剧,体内总草酸含量为对照处理的113%~169%,且主要表现为水溶性草酸含量显著高于对照,水溶性草酸含量为对照处理的135%~197%;高钙处理,李氏禾细胞膜透性、丙二醛（MDA）含量低于对照,李氏禾叶部总草酸含量为对照处理的125%~155%,且主要表现为不溶性草酸含量显著高于对照,其含量为对照处理的181%~270%。低浓度（0.2、0.4 mmol/L）铬胁迫下,高钙处理总铬含量分别为对照处理的175%和215%,高浓度（0.8、1.0 mmol/L）铬胁迫下,总铬含量与对照处理无显著差异（P>0.05）。可见,添加Ca²⁺能在一定Cr³⁺浓度胁迫下,有效缓解铬对李氏禾的毒害,且能通过提高植物体内不溶性草酸含量达到促进植物富集和耐受铬的能力。     

氧化亚铁硫杆菌浸铜研究及胞外多聚物的作用

为了获得氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans,A.f)以及胞外多聚物(extracellular polymeric sub-stances,EPS)对铜浸出的作用结果,进行了透析袋实验,设置2个处理,2者的浸出液均为成熟菌液,但一个将铜片装入透析袋中以隔离A.f及EPS与铜的直接接触。结果表明:(1)菌液的处理和加透析袋的处理中铜都得到了浸出,240 h铜的浸出浓度分别为6 796 mg/L和1 366 mg/L,可知A.f及EPS与铜片直接接触能促进铜的浸出;(2)透析袋的处理中Fe3+保持较高浓度,说明Fe3+与EPS络合后被阻挡在透析袋外面从而不能与铜反应,可知EPS在A.f浸铜中起了媒介载体的作用;(3)2者的SEM图表明无透析袋的处理A.f与铜在实验初期发生了吸附,实验后期则无,实验初期铜快速浸出是由于传质距离短,而后期速度变缓是由于传质距离增大。