Strong induction of phytochelatin synthesis by zinc in marine green alga, Dunaliella tertiolecta

Synthesis of phytochelatins (PCs), heavy-metal-sequestering peptides, in the marine green alga, Dunaliella tertiolecta, was evaluated under various conditions of exposure to heavy metals. To investigate the effect of heavy metals on both PC synthesis and their upstream biosynthetic reactions, an ion-pair-HPLC system was developed in this study, by which PCs and their biosynthetic intermediates, cysteine (Cys), gamma-glutamylcysteine (gammaEC) and glutathione (GSH), could be determined simultaneously with high sensitivity. When the cells were exposed to Zn2+, the level of PCs was maximal at 200 microM and significantly higher than that obtained after exposure to 400 microM Cd2+, which is the strongest inducer of PC synthesis in higher plants in vivo and in vitro as well as in microalgae. The predominant PC subtype was PC4, followed by PC3 and PC5, whereas PC2, which is generally abundant in higher plants, has the lowest level among PC2 to PC5. These results suggest that the characteristics of PC synthase in D. tertiolecta including the requirement of heavy metals for its catalysis and substrate specificity towards GSH and PC(n) are considerably different from those in higher plants and other algae. While PC synthesis proceeded in the heavy-metal-treated cells, the level of GSH did not appreciably change. To maintain the same size of the GSH pool, GSH must be newly synthesized to balance the amount consumed for PC synthesis.     

A tomato stem cell extract, containing antioxidant compounds and metal chelating factors, protects skin cells from heavy metal-induced damages

Heavy metals can cause several genotoxic effects on cells, including oxidative stress, DNA sequence breakage and protein modification. Among the body organs, skin is certainly the most exposed to heavy metal stress and thus the most damaged by the toxic effects that these chemicals cause. Moreover, heavy metals, in particular nickel, can induce the over-expression of collagenases (enzymes responsible for collagen degradation), leading to weakening of the skin extracellular matrix. Plants have evolved sophisticated mechanisms to protect their cells from heavy metal toxicity, including the synthesis of metal chelating proteins and peptides, such as metallothioneins and phytochelatins (PC), which capture the metals and prevent the damages on the cellular structures. To protect human skin cells from heavy metal toxicity, we developed a new cosmetic active ingredient from Lycopersicon esculentum (tomato) cultured stem cells. This product, besides its high content of antioxidant compounds, contained PC, effective in the protection of skin cells towards heavy metal toxicity. We have demonstrated that this new product preserves nuclear DNA integrity from heavy metal damages, by inducing genes responsible for DNA repair and protection, and neutralizes the effect of heavy metals on collagen degradation, by inhibiting collagenase expression and inducing the synthesis of new collagen.     

酵母菌对重金属的吸附与抗性和解毒重金属的胞内分子机制研究进展

利用有益的酵母菌去除食品基质、动物及人体的重金属污染是近年的研究热点。本文概述了多种酵母菌吸附及抗重金属的情况,并对酵母菌在重金属胁迫下的胞内解毒机制进行分析,包括谷胱甘肽合成的解毒机制、与酵母菌解毒重金属相关的基因和蛋白、转运蛋白介导的细胞内重金属的排出和液泡隔离机制及金属硫蛋白和植物螯合肽对重金属的螯合作用,重点从分子角度分析了酵母菌对重金属的解毒机制,归纳了解毒过程中关键性的基因和蛋白质以及它们的功能作用,旨在为酵母菌作为生物吸附剂应用于生态环境、被重金属污染的发酵食品及动物和人体提供依据。     

Transgenic plants in phytoremediation: recent advances and new possibilities

Phytoremediation, the use of plants and their associated microbes to remedy contaminated soils, sediments, and groundwater, is emerging as a cost-effective and environmentally friendly technology. Due in large part to its aesthetic appeal, this technology has gained increasing attention over the past 10 years. Phytoremediation uses different plant processes and mechanisms normally involved in the accumulation, complexation, volatilization, and degradation of organic and inorganic pollutants. Certain plants, called hyperaccumulators, are good candidates in phytoremediation, particularly for the removal of heavy metals. Phytoremediation efficiency of plants can be substantially improved using genetic engineering technologies. Recent research results, including overexpression of genes whose protein products are involved in metal uptake, transport, and sequestration, or act as enzymes involved in the degradation of hazardous organics, have opened up new possibilities in phytoremediation. This paper provides a critical review of the recent progress made toward the development of transgenic plants with improved phytoremediation capabilities and their potential use in environmental cleanup.     

Genes associated with heavy metal tolerance and accumulation in Zn/Cd hyperaccumulator Arabidopsis halleri: a genomic survey with cDNA microarray

To survive in variable soil conditions, plants possess homeostatic mechanisms to maintain a suitable concentration of essential heavy metal ions. Certain plants, inhabiting heavy metal-enriched or -contaminated soil, thus are named hyperaccumulators. Studying hyperaccumulators has great potential to provide information for phytoremediation. To better understand the hyperaccumulating mechanism, we used an Arabidopsis cDNA microarray to compare the gene expression of the Zn/Cd hyperaccumulator Arabidopsis halleri and a nonhyperaccumulator, Arabidopsis thaliana. By analyzing the expression of metal-chelators, antioxidation-related genes, and transporters, we revealed a few novel molecular features. We found that metallothionein 2b and 3, APX and MDAR4 in the ascorbate-glutathione pathway, and certain metal transporters in P(1B)-type ATPase, ZIP, Nramp, and CDF families, are expressed at higher levels in A. halleri than in A. thaliana. We further validated that the enzymatic activity of ascorbate peroxidase and class III peroxidases are highly elevated in A. halleri. This observation positively correlates with the higher ability of A. halleri to detoxify H2O2 produced by cadmium and paraquat treatments. We thus suggest that higher peroxidase activities contribute to the heavy metal tolerance in A. halleri by alleviating the ROS damage. We have revealed genes that could be candidates for the future engineering of plants with large biomass for use in phytoremediation.     

重金属和抗生素抗性基因在土壤中的复合污染研究进展

抗生素滥用及其诱导产生的抗生素抗性基因(antibiotic resistance genes, ARGs)污染己经引起人们的广泛关注。与此同时,环境中重金属的污染状况也呈加剧趋势,与抗生素抗性基因不同,重金属在自然环境中很难被降解,二者同时存在不仅维持和加强了环境中的微生物对重金属的原有抗性,同时增强了对抗生素抗性基因的抗性。目前,重金属污染地区的养殖业中动植物细菌传染病的抗生素治疗总是无效的,其原因可能是重金属离子和抗生素抗性基因的协同抗性在选择压力下得到增强。本文总结了我国抗生素抗性基因和重金属元素在土壤中的污染状况及其复合污染特征,综述了这2类物质在土壤中的协同选择机制和综合修复措施,以期为重金属和抗生素抗性基因带来的污染所致危害的减轻和未来复合污染相关研究的深入提供参考。     

Classification of heavy-metal toxicity by human DNA microarray analysis

Microarray technology is proving to be a useful tool to classify undefined environmental toxicants, to investigate underlying mechanisms of toxicity, and to identify candidate toxicant-specific genetic markers by examining global effects of putative toxicants on gene expression profiles. The aim of this study was to evaluate the toxicities of six heavy metals through the comparison with gene expression patterns induced by well-known chemicals. For this purpose, we first identified the genes altered specifically in HepG2 under the exposure of 2,3-dimethoxy-1,4-naphthoquinone (DMNQ), phenol, and N-nitrosodimethylamine (DMN), which were selected as the model chemicals, using DNA microarray. On the basis of the expression profiles of these genes, toxicities of six heavy metals, arsenic, cadmium, nickel, antimony, mercury, and chromium, were evaluated. The specific gene alteration and hierarchical clustering revealed that biological action of six heavy metals was clearly related to that of DMNQ which has been reported to be a reactive oxygen species (ROS) generating chemical and which induced the genes associated with cell proliferative responses. These results suggest that cell proliferative responses which are probably caused by ROS are a major apparent biological action of high-dose heavy metals, supporting the previous reports. Overall, a mechanism-based classification by DNA microarray would be an efficient method for evaluation of toxicities of environmental samples.     

Accumulation of Cu, Pb, Ni and Zn in the halophyte plant Atriplex grown on polluted soil

BACKGROUND: Three annual Atriplex species—A. hortensis var. purpurea, A. hortensis var. rubra and A. rosea—growing on soil with various levels of the heavy metals copper, lead, nickel, and zinc, have been investigated. RESULTS: Metal accumulation by Atriplex plants differed among species, levels of polluted soil and tissues. Metals accumulated by Atriplex were mostly distributed in root tissues, suggesting that an exclusion strategy for metal tolerance widely exists in them. The increased concentration of heavy metals in soil led to increases in heavy metal shoot and root concentrations of Ni, Cu, Pb and Zn in plants as compared to those grown on unpolluted soil. Accumulation was higher in roots than shoots for all the heavy metals. None of the plants were suitable for phytoextraction because no hyperaccumulator was identified. However, plants with a high bioconcentration factor and low translocation factor have the potential for phytostabilization. Similarly, the correlation between metal concentrations and translocations in plants (BCFs and TFs) using a linear regression was also statistically significant. CONCLUSION: Among the plants studied, var. purpurea was the most efficient in accumulating Pb and Zn in its shoots, whereas var. rubra was most suitable for phytostabilization of sites contaminated with Cu and Ni. Copyright © 2011 Society of Chemical Industry     

重金属污染对葡萄生化及安全品质影响的研究进展

对国内外有关重金属对葡萄生理生化、安全品质影响及缓解措施的最新研究进展进行归纳总结,旨在为相关领域研究人员系统了解葡萄对重金属污染的响应及其缓解机理提供参考。重金属污染对葡萄根系和茎生长具有抑制作用,影响氮、铁等营养元素吸收,并能使葡萄叶片卷曲,抑制光合作用。重金属胁迫会引起葡萄氧化胁迫,比如膜脂过氧化和蛋白质损伤等,进而导致植物代谢紊乱,甚至植株死亡。重金属在葡萄植株中积累因其种类和葡萄品种不同而不同,总体而言,葡萄根、茎、叶相对于葡萄果实对重金属的富集能力更强。在重金属污染的葡萄园内施用含硅材料和有机物类肥料,可以起到缓解重金属毒害,提升土壤环境质量的作用。     

乳酸菌吸附重金属的影响因素、机理及应用研究进展

重金属是环境的主要污染物之一,其难以在环境中转化,易通过食物链蓄积,严重威胁人体健康。已有研 究证明乳酸菌具有去除重金属的能力。本文概述了乳酸菌吸附重金属的影响因素和机理,并对吸附菌株的应用进行 总结,深入研究其吸附机理,并对其在食品中的应用进行展望,以期为乳酸菌吸附重金属的深入研究提供参考。     

Rapid method for detection and detoxification of heavy metal ions in water environments using phytochelation

Phytochelatins (PCs, (gammaGlu-Cys)n-Gly (n = 2-11)) are produced by higher plants, algae, and some fungi in response to heavy metal ion exposure. A rapid and convenient method for quantifying heavy metal ion concentrations in water environments was developed using a chemically synthesized PC as a mediator. The chelating ability of the PC and quantification of the thiol group were utilized to measure heavy metal ions at low concentrations. The method requires only ten minutes for measurement and only 1 ml of a liquid sample. A range of homogeneous PCs (n = 4-7) were chemically synthesized using a peptide synthesizer. These, especially PC7, exhibited higher sensitivity and consistency of measurement than the native PC from Silene cucubalus, which produced a mixture of PC2, PC3, and PC4. Detoxification of heavy metal ions in vitro by PC was also investigated. Using the paper disc method, the cell growth inhibition zone caused by cadmium ion against Salmonella typhimurium TA1538 was significantly decreased by addition of PC. Furthermore, at the minimum inhibitory concentration of cadmium ion (200 microM) in a nutrient broth culture of S. typhimurium, cell growth was almost completely recovered by addition of PC to the medium.     

Antioxidant activity of proteins and peptides

Proteins can inhibit lipid oxidation by biologically designed mechanisms (e.g. antioxidant enzymes and iron-binding proteins) or by nonspecific mechanisms. Both of these types of antioxidative proteins contribute to the endogenous antioxidant capacity of foods. Proteins also have excellent potential as antioxidant additives in foods because they can inhibit lipid oxidation through multiple pathways including inactivation of reactive oxygen species, scavenging free radicals, chelation of prooxidative transition metals, reduction of hydroperoxides, and alteration of the physical properties of food systems. A protein's overall antioxidant activity can be increased by disruption of its tertiary structure to increase the solvent accessibility of amino acid residues that can scavenge free radicals and chelate prooxidative metals. The production of peptides through hydrolytic reactions seems to be the most promising technique to form proteinaceous antioxidants since peptides have substantially higher antioxidant activity than intact proteins. While proteins and peptides have excellent potential as food antioxidants, issues such as allergenicity and bitter off-flavors as well as their ability to alter food texture and color need to be addressed.     

Molecular aspects, physiological function, and clinical significance of metallothioneins

Metallothioneins (MTs) are well-characterized low molecular weight, heat-stable cytosolic proteins with exceptional high content of cysteinyl sulfur and are known to bind heavy metals like cadmium (Cd), zinc (Zn), and copper (Cu). Since these proteins are induced on exposure to heavy metals, it is now accepted that they have a detoxifying role during heavy metal toxicity. It has also been suggested that the primary function of Mt is in the homeostasis of the essential metals Zn and Cu. Recently, a role MT in selenium metabolism in primates has been established. Further, MT has gained considerable importance in the clinical disorders related to trace metal metabolism.     

原子吸收光谱法测定食品中重金属含量的研究进展

原子吸收光谱近年来被广泛用于食品中重金属含量的测定,该方法与传统化学分析方法相比具有灵敏度更高、测定结果更准确等优点。本文综述使用原子吸收法测定蔬菜、粮食、海产品和饮品中的铅(Pb)、镉(Cd)、铬(Cr)、汞(Hg)和砷(As)等重金属元素的研究进展。对使用火焰原子吸收(FAAS)、石墨炉原子吸收(GFAAS)和氢化物发生原子吸收(HGAAS)等方法测定不同元素的准确性、灵敏度和回收率等进行评述,并对原子吸收法在食品重金属检测中的应用进行展望。     

The Bioaccumulation and Physiological Effects of Heavy Metals in Carrots,Onions, and Potatoes and Dietary Implications for Cr and Ni: A Review

The bioaccumulation of heavy metals in food tubers (carrots, onions, and potatoes) as a result of polluted irrigation water has been studied in this review paper. Given that heavy metals can cause a considerable oxidative stress, the impact of these metals to the physiology of the plants has also been assessed. The consumption of vegetables cross‐contaminated with heavy metals carries a considerable risk for humans (especially for children and pregnant women) and these dietary implications are discussed while European Food Safety Authority has been urged to look into this matter of concern.     

Accumulation and distribution of cadmium and lead in wheat (Triticum aestivum L.) grown in contaminated soils from the oasis, north-west China

BACKGROUND: Crops grown in soils contaminated by heavy metals are an important avenue for toxic metals entering the human food chain. The objectives of our study were to investigate the accumulation and distribution of cadmium (Cd) and lead (Pb) in wheat plants cultivated in arid soils spiked with different doses of heavy metal, as well as bioavailability of these metals in the contaminated arid soils from the oasis, north‐west China. RESULTS: The concentrations of Cd in the roots of wheat plants were about 5, 14 and 8 times higher than those in the shoots, shells and grains, respectively. The concentrations of Pb in the roots were about 23, 76 and 683 times higher than those in the shoots, shells and grains, respectively. Grains contained 11–14% and 0.1–0.2% of Cd and Pb found in roots of wheat plants. The bioconcentration factor (BCF) is the ratio of metal concentration in plant tissues and metal concentration in their rooted soils. The average BCF of Cd and Pb in grains was 0.6270 and 0.0007. Cd and Pb contents in different parts of wheat plants mainly correlated with the bound‐to‐carbonate metal fractions in contaminated arid soils. CONCLUSION: The preliminary study indicated that Cd and Pb were predominantly accumulated and distributed in wheat roots and shoots, and only a small proportion of these metals can reach the grains. The carbonate fractions mainly contributed to Cd and Pb bioavailability in contaminated arid soils. Copyright © 2010 Society of Chemical Industry     

植物源生物活性肽的研究进展

生物活性肽是一类对生物机体有益且易被机体吸收的小分子聚合物,是由2～20个氨基酸组成的蛋白质片段,其功能性质由氨基酸组成和排列顺序决定。植物是生物活性肽的天然宝库,植物源生物活性肽种类丰富、结构新颖,是近年来的研究热点。生物活性肽被视为营养保健品和功能食品成分,除了含有丰富的营养价值之外,还具有抗氧化、降血压、抑菌、降血脂和维持血糖水平平衡等功能,可利用其功能治疗、控制和预防慢性疾病,对食品、医药和美容等领域的发展具有重要意义。本文综述了近5年从植物中获取生物活性肽的最新进展,系统地总结了抗氧化肽、降压肽、抗菌肽、降血糖肽和降血脂肽的作用机制,与目前最常见的健康问题进行对应说明。对生物活性肽的制备方法、分离纯化和鉴定技术进行总结比较,并对生物活性肽的未来发展趋势以及在实际应用中遇到的问题进行展望,为未来植物源生物活性肽的进一步研究开发与应用提供参考。     

重金属复合污染对茶叶重金属、主要生化成分含量及冲泡茶汤浸出率的影响研究

通过土壤盆栽实验,研究四种重金属As、Pb、Cr、Cd复合污染对茶叶重金属含量及主要生化成分含量的影响,同时研究了不同冲泡次数下茶汤中四种重金属的浸出率。结果表明:复合污染条件下,茶叶中重金属积累量显著高于对照,其高低顺序为Pb>Cr>Cd>As,其中,Cd在盆栽土壤中的添加量低于As,但在茶叶中的积累量高于Cd,表明Cd在茶树体内的迁移率高于As。复合污染茶叶中的氨基酸和咖啡碱含量均低于对照,酚氨比值高于对照,从而降低了茶叶品质。四种重金属元素在茶汤中的浸出量均随着冲泡次数的增加而减少,Cd、Cr、Pb和As的总浸出率分别为:18.0%~35.7%、14.8%~26.8%、15.4%~31.9%和13.7%~22.1%,Pb和Cd的浸出率大于Cr和As;四种重金属元素之间的络合作用,会影响重金属在茶叶中的累积量和茶汤中的浸出量。      

核酸适配体技术在食品重金属检测中的应用研究进展

近年来食品中重金属超标对人们健康构成了威胁,所以对食品中重金属检测技术的开发成为了重要研究内容。虽然传统的检测技术对重金属进行了高选择性和高灵敏度的检测,但是仍需要一种简单、快速、有效、成本低廉的方法用于食品安全领域的快速检测。核酸适配体为一段单链DNA或者RNA序列,是经体外筛选技术筛选出的能特异结合蛋白质或其他小分子物质的寡聚核苷酸片段。核酸适配体具有靶分子广、灵敏度高、特异性强、稳定性好等特点,因而被广泛用于食品安全检测领域。本文综述近年来核酸适配体技术对食品中Hg2＋、As3＋、Pb2＋的检测,并对核酸适体技术在食品重金属检测领域的应用前景进行了展望。