Construction and evaluation of a metal ion biosensor

Escherichia coli, genetically engineered with a mercury(II)-sensitive promoter and the lux genes from Vibrio fischeri, were used as microbial bioluminescent sensors for the detection of mercury. Evaluation of this genetic construction was carried out by determining the effects of various parameters on cell suspensions maintained at constant conditions in a small 100-mL vessel. The strongest light intensities and quickest induction times occurred with cells in the midexponential growth phase maintained at 28 degrees C, concentrated to 1 x 10(9) cells/mL, mixed at very fast speeds, and aerated at 2 vvm (volume of air per volume of culture per minute) during light measurement in the small vessel. The cells were sensitive to the mercuric ion in the range of 20 nM to 4 muM (4 to 800 ppb), and the total response time was on the order of 1 hour, depending on the above parameters. The cells exhibited great specificity for mercury. The cells had almost equal specificity for organic and inorganic forms of the mercuric ion and responded more weakly to the mercurous ion. A simple, inexpensive, durable miniature probe (3 mL) was constructed and operated using the optimum parameters found in the small vessel as a guide. The range of sensitivity to the mercuric ion detected in the probe was 10 nM to 4 muM when aeration was provided. (c) 1993 John Wiley & Sons, Inc.     

Influence of the activated sludge system configuration on heavy metal toxicity reduction

The effect of configuration of activated sludge systems on heavy metal toxicity was investigated. Two bench-scale completely mixed activated sludge systems were operated identically in order to determine the toxic effects of Cr(VI), Zn(II) and industrial wastewater on the activated sludge biomass. One system was operated with an aerobic selector and the other without. Batch experiments based on OECD 209 (Organisation for Economic Cooperation and Development) were performed using a respirometer to find out potential toxicity reduction effect of an aerobic selector. The IC₅₀ (concentration of a chemical that exhibits 50% respiration inhibition) values of Cr(VI), Zn(II) and industrial wastewater in the activated sludge were determined. Results indicated that the heavy metals and industrial wastewater caused less inhibitory effect on the selector activated sludge system in comparison to the conventional activated sludge system. Cr(VI) was found to exert higher inhibition on both systems.     

Comparison of the toxicity of heavy metals to cabbage growth

Summary Cabbage plants were grown for 55 days with a nutrient solution containing 1 and 10 ppm of V, Cr(III), Cr(VI), Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg(I), orHg(II). A comparison of the plant growth and chemical analysis revealed that Cr(VI), Cu, Cd, and Hg(II) in the solution are most toxic to the plant growth (hence detrimental to the cabbage-head formation) and Mn, Fe, and Zn are less toxic than other heavy metals, and that Mn, Zn, Co, Ni, and Cd and translocated into all the plant organs while V, Cr(III), Cr(VI), Fe, Cu, Hg(I), and Hg(II) are accumulated in the roots.     

An amperometric biosensor based on horseradish peroxidase immobilized onto maize tassel-multi-walled carbon nanotubes modified glassy carbon electrode for determination of heavy metal ions in aqueous solution

A biosensor for trace metal ions based on horseradish peroxidase (HRP) immobilized on maize tassel-multiwalled carbon nanotube (MT-MWCNT) through electrostatic interactions is described herein. The biosensor was characterized using Fourier transform infrared (FTIR), UV–vis spectrometry, voltammetric and amperometric methods. The FTIR and UV–vis results inferred that HRP was not denatured during its immobilization on MT-MWCNT composite. The biosensing principle was based on the determination of the cathodic responses of the immobilized HRP to H₂O₂, before and after incubation in trace metal standard solutions. Under optimum conditions, the inhibition rates of trace metals were proportional to their concentrations in the range of 0.092–0.55 mg L⁻¹, 0.068–2 mg L⁻¹ for Pb²⁺ and Cu²⁺ respectively. The limits of detection were 2.5 μg L⁻¹ for Pb²⁺ and 4.2 μg L⁻¹ for Cu²⁺. Representative Dixon and Cornish-Bowden plots were used to deduce the mode of inhibition induced by the trace metal ions. The inhibition was reversible and mixed for both metal ions. Furthermore, the biosensor showed good stability, selectivity, repeatability and reproducibility.     

食品中重金属的存在形态及其与毒性的关系

简要介绍了近年来有关食品中重金属形态及其毒性关系的研究进展,归纳了食品中重金属的化学形态特征、不同类型食品中重金属的存在形态、食品中重金属形态与生物有效性和毒性的关系,以及该领域中急需研究解决的问题．     

Hesperidin ameliorates heavy metal induced toxicity mediated by oxidative stress in brain of Wistar rats

Cadmium (Cd) induces neurotoxicity owing to its highly deleterious capacity to cross the blood brain barrier (BBB). Recent studies have provided insights on antioxidant properties of bioflavonoids which have emerged as potential therapeutic and nutraceutical agents. The aim of our study was to examine the hypothesis that hesperidin (HP) ameliorates oxidative stress and may have mitigatory effects in the extent of heavy metal-induced neurotoxicity. Cd (3 mg/kg body weight) was administered subcutaneously for 21 days while HP (40 mg/kg body weight) was administered orally once every day. The results of the current investigation demonstrate significant elevated levels of oxidative stress markers such as lipid peroxidation (LPO) and protein carbonyl (PC) along with significant depletion in the activity of non-enzymatic antioxidants like glutathione (GSH) and non-protein thiol (NP-SH) and enzymatic antioxidants in the Cd treated rats’ brain. Activity of neurotoxicity biomarkers such as acetylcholinesterase (AchE), monoamine oxidase (MAO) and total ATPase were also altered significantly and HP treatment significantly attenuated the altered levels of oxidative stress and neurotoxicity biomarkers while salvaging the antioxidant sentinels of cells to near normal levels thus exhibiting potent antioxidant and neuroprotective effects on the brain tissue against oxidative damage in Cd treated rodent model.     

Retromobilization of heavy metal resistance genes in unpolluted and heavy metal polluted soil

Abstract: Retromobilization of the nonconjugative (Tra⁻Mob⁺) IncQ vector, pMOL155, and the non-mobilizable (Tra⁻Mob⁻) vector, pMOL149, by means of the IncP plasmids RP4 and pULB113 (RP4::Mu3A), was studied in plate matings and in soil microcosms, and compared with direct and triparental mobilization. Both vectors harbour the czc genes, originating from Alcaligenes eutrophus , which code for resistance to Co, Zn, and Cd. The donor of the czc genes was Escherichia coli which did not express these genes. The recipient, Alcaligenes eutrophus , expressed the czc genes very well. Retromobilization, direct and triparental mobilization of pMOL155 was observed in sterile soil. Both the addition of nutrients and heavy metals significantly enhanced the number of (retro)transconjugants. Retromobilization was also detected in nutrient amended nonsterile soil, but the presence of the autochthonous soil biota strongly reduced the number of retrotransconjugants and also prevented their increase upon application of heavy metals to the soil. Retromobilization of the czc genes, cloned in pMOL149, by using pULB113 was also observed, yet only in sterile, nutrient amended, heavy metal polluted soil.     

Development of an automated water toxicity biosensor using Thiobacillus ferrooxidans for monitoring cyanides in natural water for a water filtering plant

An on-line biosensor consisting of immobilized Thiobacillus ferrooxidans and an oxygen electrode was developed for automated monitoring of acute toxicity in water samples. T. ferrooxidans is an obligatory acidophilic, autotrophic bacterium and derives its energy by the oxidation of ferrous ion, elemental sulfur, and reduced sulfur compounds including metal sulfides. The assay is based on the monitoring of a current increase by addition of toxicoids, which is caused by the inhibition of bacterial respiration and decrease in oxygen consumption. Optimum cell number on the membrane was 5.0 x 10(8) cells. The steady-state current was obtained when concentration of FeSO4 was above 3.6 mM at pH 3. The sensor response of T. ferrooxidans immobilized membrane for 5.0 microM KCN was within an error of 10% for 30 membranes. A linear relationship was obtained at KCN concentration in the range of 0.5-3.0 microM in a flow-type monitoring system. Minimum detectable concentrations of KCN, Na2S, and NaN3 were 0.5, 1.2, and 0.07 microM, respectively. The monitoring system contained two biosensors and these sensors were cleaned with sulfuric acid (pH 1.5) twice a day. This treatment could remove fouling on microbial immobilized membrane by natural water and ferrous precipitation in the flow cell. This flow-type monitoring sensor was operated continuously for 5 months. Also, T. ferrooxidans immobilized membrane can be stored for one month at 4 degrees C when preserved with wet absorbent cotton under argon gas.     

重金属污染对昆虫生长发育的影响

重金属污染已经成为一个全球性的环境问题,对生物多样性和人类健康构成了严重威胁。作为全球生物多样性的重要组成部分,昆虫因重金属污染而受到的潜在影响同样引起了人们的普遍关注。过量重金属可对昆虫的生长发育产生影响。环境中的重金属可通过昆虫的呼吸、表皮和摄食等途径进入昆虫体内,进入昆虫体内的过量重金属不仅能引起昆虫细胞超微结构的变化和遗传物质的改变,还可诱导昆虫细胞凋亡并影响细胞的活力和增殖。但昆虫能将过量的重金属以金属颗粒形式储存在具消化、存储或分泌功能的器官中,也能将其转运至溶酶体中解毒。同时,金属结合蛋白和抗氧化酶在昆虫对重金属的解毒过程中具有重要作用。     

重金属胁迫下内生菌对宿主植物的解毒机制

采用内生菌联合植物修复是土壤重金属污染修复理论研究和应用实践的新思路。较之根际促生菌,内生菌因生存环境稳定且与植物联系更加紧密,在实际应用中具有更大价值。在重金属胁迫下,部分具有特定功能的细菌可进入植物体内成为内生菌,这些内生菌通常在重金属吸收、耐受和解毒方面具有优良的特性,而且可以协同宿主植物耐受重金属胁迫,表现在直接或间接降低植物体内重金属胁迫强度和提高植物本身对重金属的耐受性两方面。系统分析了内生菌对宿主植物的解毒机制,综述了近年来内生菌增强植物重金属耐受性的研究,展望了重金属胁迫下植物和内生菌互作机制的研究思路和方向。     

The composition of pyrophosphate heavy metal detoxification granules in barnacles

A major detoxification mechanism involving the binding of excess metals to inorganic, insoluble metalliferous granules occurs in many invertebrates. X-ray microanalysis of granules extracted from the barnacles Elminius modestus Darwin and Semibalanus balanoides (L.) (Crustacea: Cirripedia) indicated that one granule type was predominant. Examples of this granule type usually contained Fe and P, or Zn and S, or a combination of all four elements as major constituents. The predominant form of P in the granules was pyrophosphate, P₂O⁴⁻₇, with oprthophosphate and other polyphosphates present in lower amounts. The S was present as organic S. Biochemical analysis showed high levels of Ca, Fe, Mg, K and Zn in the granules with Cu and Ag present in smaller quantities. Considerable variation was shown between granules.     

Contribution of the arbuscular mycorrhizal symbiosis to heavy metal phytoremediation

High concentrations of heavy metals (HM) in the soil have detrimental effects on ecosystems and are a risk to human health as they can enter the food chain via agricultural products or contaminated drinking water. Phytoremediation, a sustainable and inexpensive technology based on the removal of pollutants from the environment by plants, is becoming an increasingly important objective in plant research. However, as phytoremediation is a slow process, improvement of efficiency and thus increased stabilization or removal of HMs from soils is an important goal. Arbuscular mycorrhizal (AM) fungi provide an attractive system to advance plant-based environmental clean-up. During symbiotic interaction the hyphal network functionally extends the root system of their hosts. Thus, plants in symbiosis with AM fungi have the potential to take up HM from an enlarged soil volume. In this review, we summarize current knowledge about the contribution of the AM symbiosis to phytoremediation of heavy metals.     

Heavy metals toxicity in plants: An overview on the role of glutathione and phytochelatins in heavy metal stress tolerance of plants

Plants experience oxidative stress upon exposure to heavy metals that leads to cellular damage. In addition, plants accumulate metal ions that disturb cellular ionic homeostasis. To minimize the detrimental effects of heavy metal exposure and their accumulation, plants have evolved detoxification mechanisms. Such mechanisms are mainly based on chelation and subcellular compartmentalization. Chelation of heavy metals is a ubiquitous detoxification strategy described in wide variety of plants. A principal class of heavy metal chelator known in plants is phytochelatins (PCs), a family of Cys-rich peptides. PCs are synthesized non-translationally from reduced glutathione (GSH) in a transpeptidation reaction catalyzed by the enzyme phytochelatin synthase (PCS). Therefore, availability of glutathione is very essential for PCs synthesis in plants at least during their exposure to heavy metals. Here, I reviewed on effect of heavy metals exposure to plants and role of GSH and PCs in heavy metal stress tolerance. Further, genetic manipulations of GSH and PCs levels that help plants to ameliorate toxic effects of heavy metals have been presented.     

多孔硅Bragg反射镜适配子生物传感器检测心肌肌钙蛋白I

通过脉冲腐蚀法制备多孔硅Bragg反射镜,将心肌肌钙蛋白I（cTnI）适配子共价固定到多孔硅Bragg反射镜的孔洞中,发现适配子能与cTnI分子特异性结合。定量分析不同浓度的cTnI与适配子结合后多孔硅Bragg反射镜的反射谱峰位的红移情况。结果表明：基于多孔硅Bragg反射镜适配子生物传感器的光学检测具有良好的特异性,且具有免标记及检测时间短等优异性能。传感器的线性检测范围0．05-4nmol／L,最低检测限为0．05nmol／L。     

植物螯合肽及其在重金属耐性中的作用

综述植物螯合肽的生物合成及其在重金属耐性中的作用．有毒重金属在土壤中的积累不仅影响作物的生长和产量形成,而且严重威胁农产品的安全性．植物对重金属的耐性和积累在种间和基因型之间存在着很大的差异,在重金属胁迫条件下植物螯合肽(PC)的合成是植物对胁迫的一种适应性反应,耐性基因型合成较多的PC谷胱苷肽是合成PC的前体,PC可与重金属螯合,并进一步转运至液泡贮存,使细胞质的重金属浓度降低,从而达到解毒效果．重金属诱导植物合成PC的遗传机理和生化途径有赖于分子生物学的深入研究,cD-敏感型拟南芥突变体Cad1-1(缺失GSH)和Cad2-1(缺失PC合成诱导酶)的分离及相关研究,佐证了PC在Cd-解毒中起关键作用．对PC在重金属污染土壤或水体的植物修复和农作物安全生产中的意义进行了讨论．     

Submitochondrial particles asin vitro biosensors of heavy metal toxicity

The effects on mitochondrial respiratory parameters of heavy metals, such as Cu, Ni, Pb, Cd, Zn, Ag, Hg, were recorded by using thein vitro response of submitochondrial particles (SMP) from beef heart mitochondria.The toxicity of these elements was estimated by determining their effects on the energy-coupled reverse electron transfer (RET), which is induced by ATP and succinate at first site level of the respiratory chain in SMP.The RET rate was easily monitored by recording spectrophotometrically at 340 nm the production of NADH, arising from the reduction of exogenous NAD⁺ by RET.The toxicity values were expressed as the toxicant molar concentration which decreases the rate of reduction of NAD⁺ to an extent of 50 percent (EC50). The toxicity increased in the following order: Ni²⁺2+2+< Cd²⁺2+2++.The SMP data were compared with the toxicity values obtained from a variety of biological systems currently used for toxicity testing. The results obtained demonstrate that the SMP test generally provides a good estimate of metal toxicity for several fish and invertebrate species. This is demonstrated by the statistical parameters obtained in the regression analysis. The broadened 95% confidence intervals and, in particular, the poor correlations obtained for some aquatic organisms can be ascribed to the more complex metabolic interactions and competing toxic pathways in aquatic organisms, when compared to SMP.     

The effect of endophytic Peyronellaea from heavy metal-contaminated and uncontaminated sites on maize growth,heavy metal absorption and accumulation

Heavy metal (HM) tolerance, effects on maize growth, heavy metal absorption and accumulation by endophytic Peyronellaea from HM-contaminated and uncontaminated sites were studied to evaluate the hypothesis that endophytes from HM-contaminated sites would enhance HM-tolerance in hosts. Although we found that certain endophytes improved tolerance of plants to heavy metals, isolates from the HM-contaminated site were not more tolerant to heavy metals than those from the uncontaminated site. Pot experiments indicated that growth and heavy metal absorption and accumulation by host plants in HM-polluted environments could be affected by inoculation with HM-tolerant endophytic fungi, and isolates showed a high intraspecific variability. However, there was no significant difference in growth between the maize inoculated with the endophytes from the HM-contaminated site and uncontaminated site under lead stress. Similarly, the HM content in the shoots and roots of maize inoculated with the isolates from the HM-contaminated site was not always higher than that in maize inoculated with endophytes from the uncontaminated site. Therefore, based on our experiments it is suggested that HM-tolerance due to endophytes and their effects on host plant growth and heavy metal absorption and accumulation were not correlated with origin of the endophytes.     

上海地区绿化树种重金属污染防护特性的研究

通过测定土壤样品的重金属含量,调查了上海七宝镇污染水系两侧与上海宝钢集团厂区的重金属污染状况。结果表明,在污染水系两侧重金属含量较对照稍高,而上海宝钢厂区各样点土壤重金属含量明显高于对照,存在较严重的污染．同时在这两处重金属污染地带观察记录了绿化树种的生长状况,采集植物样品以ICP仪进行树木样品的重金属含量分析,综合两方面数据对近20种常见绿化树种的重金属污染的防护特性进行了比较研究．结果表明,法国冬青、紫薇、木芙蓉、女贞和龙柏等植物种类富集重金属能力较强,且生长状况较为良好,最适于作为重金属污染厂区的生态防护绿化的主要树种;而蚊母、夹竹桃和石楠等植物种类虽然富集重金属能力较低,但有较强的耐性,能良好生长。也适于作为污染区绿化美化树种。     

株洲工业区土壤重金属污染与蚯蚓同工酶的研究

用聚丙烯朊胺凝胶圆盘电泳法对蚯蚓酯酶及过氧化物酶同工酶进行比较研究,结果表明,重金属在蚯蚓体内富集量随污染程度增加而上升,重污染区为中污染区的２．２７倍,为轻污染区的７．３０倍,重污染区Ｃｄ、Ｐｂ、Ａｓ在蚯蚓体内分别达到４７．３、３５．２、１６．３２μｇ．ｋｇ＾－１。其秩相关系数（ｒ５）〉０．６６－０．７７。蚯蚓酯酶同工酶酶带减少,酶活性降低,而其过氧化物酶酶带和酶活性有所增加。     

The metal distribution and the change of physiological and biochemical process in soybean and mung bean plants under heavy metal stress

Soybean [Glycine max (Linn.) Merrill] and mung bean [Vigna radiate (Linn.) Wilczek] plants were challenged with 5 kinds of heavy metals [cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb) and mercury (Hg)] in a hydroponic system. We applied 4 different metal treatments to study the effects of heavy metals on several physiological and biochemical parameters in these species, including root length, heavy metal concentrations and allocation in different organs, superoxide dismutase, catalase, and peroxidase activities, the content of malondialdehyde (MDA), protein and chlorophyll. The data showed that the growth of the roots of soybean and mung bean was equally sensitive to external Hg concentrations. Soybean was more sensitive to external Cd concentrations, and mung bean was more sensitive to external Cr, Cu and Pb concentrations. Normal concentrations of heavy metal would not cause visible toxic symptoms, and a low level of heavy metal even slightly stimulated the growth of plants. With the rise of heavy metal concentration, heavy metal stress induces an oxidative stress response in soybean and mung bean plants, characterized by an accumulation of MDA and the alternation pattern of antioxidative enzymes. Meanwhile, the growth of plants was suppressed, the content of chlorophyll decreased and leaves showed chlorosis symptoms at high metal concentrations.