Large plasmids governing multiple resistances to heavy metals: A genetic approach∗

Gram negative bacteria classified as Alcaligenes eutrophus and carrying large resistance plasmids (generally two) were found in various industrial sites highly contaminated by heavy metals (Zn⁺⁺, Cu⁺⁺, Co⁺⁺,...). These strains were detected by DNA hybridization with a probe made with a 9kb fragment (ccz⁺ fragment) encoding for resistances to Cd⁺⁺, Co⁺⁺ and Zn⁺⁺, and cloned from plasmid pMOL30. This plasmid was isolated from the representative strain A. eutrophus CH34 which harbours the plasmids pMOL30 (240 kb) and pMOL28 (165 kb). Phenotypes related to pMOL28 and pMOL30 include the tolerance to Cd⁺⁺, Co⁺⁺, Cr0₄ ⁼, Cu⁺⁺, Hg⁺⁺, Ni⁺⁺, Pb⁺⁺ and Zn⁺⁺. The described genetic properties of these plasmids refer to some cloned or mapped functions and to some plasmid rearrangements. Plasmid pMOL85 (250 kb) which is related to pMOL30 was also described. Its host (A. eutrophus DS185) was isolated from a zinc desert. pMOL85 can efficiently self transfer in plasmidfree derivatives.     

Acclimation and tolerance of Artemia salina to copper salts

The brine shrimp Artemia salina L. was acclimated in sea water with cupric chloride, acetate, carbonate, and sulphate, each at concentrations of 0.1, 0.05 and 0.025 ppm Cu⁺⁺, together with sea water controls. Growth inhibition was observed in all four compounds, generally in direct relationship to the concentration. It was least in sulphate, and increased progressively in chloride, acetate and carbonate in that order. No inhibition however was observed in carbonate at 0.025 ppm Cu⁺⁺. In toxicity tests, 2-week old larvae from each solution were exposed to concentrations of 10, 7.5, 5, 2.5 and 1 ppm Cu⁺⁺ of the same compounds, together with unacclimated larvae of the same age. Similar tests were held with 6-week old adults acclimated (a) in 0.1 ppm Cu⁺⁺ (chloride, acetate and sulphate) using the same concentrations and (b) in 0.5 ppm Cu⁺⁺ (carbonate), using 150, 125, 100, 75, and 50 ppm Cu⁺⁺. Toxicity to unacclimated larvae and adults differed with the compounds, carbonate being the least toxic, followed by sulphate, chloride and acetate in increasing order. Larvae acclimated in chloride (0.025 ppm Cu⁺⁺) and sulphate (0.1 and 0.5 ppm Cu⁺⁺) showed an increased tolerance to 1 and 2.5 ppm Cu⁺⁺ compared to untreated controls. Tolerance was not enhanced from 5 ppm Cu⁺⁺ upwards. In both compounds, adults acclimated in 0.1 ppm Cu⁺⁺ showed an increased tolerance to concentrations between 1 and 7.5 ppm Cu⁺⁺ compared to controls. Larval mortality in carbonate was below 50% in all test solutions. Adults acclimated at 0.5 ppm Cu⁺⁺ showed an increased tolerance to 50 ppm Cu⁺⁺ compared to controls. Considerable precipitation occurred with the high levels of this compound, thus effecting the final concentrations. No acclimation effect was observed in acetate for either larvae or adults. It is suggested that in A. salina, copper toxicity depends on the particular form of the metal, and that this difference is also evident in growth inhibition and in the potential acquisition of increased tolerance through exposure to low concentrations.     

Immobilization of some metals in contaminated sludge by zeolite prepared from local materials

In this study, zeolite was prepared from cheap local Egyptian clay (kaolin) and characterized by X-ray diffraction, X-ray fluorescence spectroscopy, SEM. The prepared zeolite was used as a binder for immobilization of the metals Cd²⁺, Cu²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ in contaminated sewage sludge. Different leaching tests were conducted to determine the efficiency of the prepared zeolite for metal stabilization. The leaching of the metals from stabilized sludge decreased as the zeolite amount increased. It was found that 10% of zeolite is sufficient for the stabilization of all metal ions under investigation. It was suggested that the metal uptake mechanism by zeolite was by an ion-exchange mechanism. Examination of the solidified sample for its compressive strength after curing for 28 days yielded a value of 0.83?MPa, which indicates that the treated sludge was well solidified and safe to be used in a wide variety of applications, for instance as a raw material for pavement blocks.     

Utilization of fly ash in adsorption of heavy metals from wastewater

The aim of this study was to assess the toxicity reduction of wastewaster after treatment with fly ash. Fly ash is a waste material which is formed as a result of coal burning in power plants, but has the potential to adsorb heavy metal ions. The present study examined the adsorption capacity of fly ash to adsorb Pb²⁺, Cu²⁺, and Zn²⁺ from waste water under different conditions of contact time, pH, and temperature. Uptake of metal ions by fly ash generally rose with increasing pH. At lower temperatures the uptake of heavy metal adsorption were enhanced. Significant reduction in Pb²⁺ (79%), Cu²⁺ (53%), and Zn²⁺ (80%) content was found after treatment with fly ash of waste water treatment. Using the microtox test toxicity of the effluent was reduced by 75% due to removal of Pb²⁺ ion by the fly ash. Data indicated that fly ash generated by power plants may be used beneficially to remove metals from waste water.     

Molecular dynamics of stability and structures in phytochelatin complexes with Zn,Cu, Fe,Mg, and Ca: Implications for metal detoxification

Phytochelatins, or (γ-glutamyl-cysteine) _n -glycine, are specialized peptides produced by plants and algae to mitigate toxic metal exposure, for instance in response to high levels of metals such as Cu, Cd, and Zn. Stability constants and structural characterization of metal–phytochelatin complexes are lacking. This information is required to gain mechanistic insights on the metal selectivity of phytochelatins. Here, we studied structural coordination and thermodynamic stability by performing molecular dynamics simulations of a fully hydrated phytochelatin molecule complexed with Ca²⁺, Mg²⁺, Fe²⁺, Zn²⁺, and Cu²⁺. Our results predict the following decreasing order for the thermodynamic stability of the phytochelatin complexes: Zn²⁺ ≥ Cu²⁺ ≥ Fe²⁺ > Mg²⁺ > Ca²⁺. The favorable binding energies with Zn²⁺ and Cu²⁺ over the other metal cations can be explained by shorter binding distances and greater coordination from carboxylate and keto O atoms. Conformational rearrangement of phytochelatin following metal chelation was captured by monitoring changes in the solvent-accessible volume. Accessibility of solvent molecules to the phytochelatin structure was inversely proportional to the distance between the coordinated ligands and the chelated metal. These new findings demonstrate the influence of the metal–phytochelatin structure on the metal-binding thermodynamics and the phytochelatin conformation, both of which are important to evaluate the intracellular role of phytochelatin in mediating algal response to toxic heavy metal exposure.     

Oxidized multiwalled carbon nanotubes modified with 2-(2-hydroxy-5-nitrophenyl)-4,5-diphenyl imidazole for solid phase extraction and preconcentration of some metal ions

In this work, a new procedure for the enrichment of the trace amount of Cu²⁺, Ni²⁺, Co²⁺, Pb²⁺, Fe²⁺, and Zn²⁺ ions based on the utilization of multiwalled carbon nanotubes (MWCNT) modified with 2-(2-hydroxy-5-nitrophenyl)-4,5-diphenyl imidazole as chelating agent prior to their determination by flame atomic absorption spectrometry has been described. The influence of effective parameters including pH, amount of ligand and MWCNT, composition of eluent, and coexisting ions on recoveries of understudy metal ions was examined. At the optimum pH of 5.0, all metal ions were quantitatively sorbed onto the proposed solid phase and completely desorbed with 8?mL of 5.0?mol?L^?1 HNO₃. The detection limit of Cu²⁺, Co²⁺, Ni²⁺, Pb²⁺, Fe²⁺, and Zn²⁺ ions was 1.7, 2.4, 2.3, 2.9, 2.8, and 1.4?µg?L^?1, while the preconcentration factor was 63 for Cu²⁺ and 94 for the other metal ions and relative standard deviations between 1.8 less than 3.0%. The proposed procedure was applied for the analysis of various samples.     

水环境中重金属铜暴露下青鳉鱼的行为响应

本研究采用生物行为传感器监测青鳉鱼重金属铜暴露下的行为数据,分析不同暴露浓度(20、10、5、1和0.1 TU)下青鳉鱼的行为响应。20、10、5、1和0.1 TU的暴露浓度下青鳉鱼对重金属污染的行为反应模式符合环境胁迫阈值模型,且不同浓度梯度重金属对青鳉鱼产生不同的行为毒性效应。通过本研究,利用重金属作用下青鳉鱼的行为变化来研究重金属环境胁迫导致的生物行为响应机制,从而得到重金属暴露下生物行为的实时变化过程和趋势,可对水环境生态系统质量进行综合评价。     

Metal removal with two biochars made from municipal organic waste: adsorptive characterization and surface complexation modeling

The adsorptive characteristics of biochar produced from garden green waste (S-char) and a mixture of food waste and garden green waste (FS-char) were investigated. Adsorption of Cu²⁺, Zn²⁺, and Mn²⁺ onto the two biochars reached equilibrium within 48 hours. The metal adsorption was effectively described by the pseudo-second-order kinetic and Freundlich isotherm models which suggest heterogeneous chemisorption. The initial solution pH influenced adsorption of Zn²⁺ and Mn²⁺ but not of Cu²⁺. Simulation via a surface complexation model showed that the fraction of XOCu⁺ adsorbed onto biochar was increased with increasing pH until it reached the adsorption maximum at pH 8.5, while the endpoint for the maximum of XOMn⁺ was higher than pH 12.     

水环境中重金属铜暴露下青鳉鱼的行为响应

采用生物行为传感器监测青鳉鱼在重金属铜暴露下的行为数据,分析不同暴露浓度(20、10、5、1和0.1 TU)下青鳉鱼的行为响应。20、10、5、1和0.1 TU的暴露浓度下青鳉鱼对重金属污染的行为反应模式符合环境胁迫阈值模型,且不同浓度梯度重金属对青鳉鱼产生不同的行为毒性效应。利用重金属作用下青鳉鱼的行为变化来研究重金属环境胁迫导致的生物行为响应机制,从而得到重金属暴露下生物行为的实时变化过程和趋势,可对水环境生态系统质量进行综合评价。     

Voltammetric analysis of metallothioneins and copper (II) in fish for water biomonitoring studies

An major research area in environmental chemistry is the development of methods for the analysis of biomarkers. Metallothioneins are used as biomarkers in studies of heavy metals exposure in water, because metallothioneins are synthesized and accumulated when organisms are exposed to toxic concentrations of pollutants. In this work, simple and sensitive voltammetric methods were developed for metallothionein and copper (II) determinations in fish liver Lepomis gibbosus. Both analytical methodologies were optimized and applied to samples extracted from individuals previously submitted to sub-lethal toxicological trials with copper sulphate (CuSO₄) and cadmium chloride (CdCl₂). The obtained results showed that both methods are very precise, sensitive, and involve simple sample preparation processes. Moreover, metallothioneins showed better correlation with the toxic exposure than Cu²⁺. To the best of our knowledge, this is the first time that hepatic metallothioneins and Cu²⁺ contents are voltammetrically determined in order to be compared in their function as heavy metal biological indicators.     

Single and combined effects of heavy metals and hormones on lysosomes of haemolymph cells from the mussel Mytilus galloprovincialis

Effects of heavy metals on lysosomes were studied in living cells from the mussel (Mytilus galloprovincialis Lam.). Haemolymph cells were obtained from the mussel adductor muscle, stained with neutral red (NR), and analysed by digital imaging to evaluate NR retention times within lysosomes. Exposure to Hg²⁺, Cd²⁺ and Cu²⁺ induced a reduction of NR retention time, indicating lysosomal membrane destabilisation. The intensity of these effects was correlated with the metal affinity for sulfhydryls. In contrast, Zn²⁺ showed no effect on lysosomes. Moreover, 200 μM Zn²⁺ protected lysosomes against the effects of Cd²⁺ and Cu²⁺, but not against Hg²⁺. Cell loading with the fluorescent pH probe Lyso Sensor followed by digital imaging showed a rise of lysosomal pH induced by Cd²⁺ and Hg²⁺, while Zn²⁺ prevented the effect of Cd²⁺ and also partially that of Hg²⁺. The different protective effect of Zn²⁺ against Hg²⁺ suggests a dual action of Hg²⁺ on lysosomes, possibly involving both membrane destabilisation and proton pump inhibition. Cell exposure to 17 β-estradiol also caused a reduction of NR retention time, which was synergistic to that of Hg²⁺. This suggests a common pathway between metals and hormone, possibly involving Ca²⁺ signaling. Received: 17 November 1999 / Accepted: 29 June 2000     

Synthesis and characterization of an ion exchanger based on tamarind kernel powder and its application for removal of some metal ions from industrial effluents

A resin synthesized from tamarind kernel powder possesses high selectivity for metal ions. Distribution coefficients for some metal ions has been determined by the batch method. The influence of pH on ion exchange capacity and K _d value of metal ions were studied. The resin has been characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, chemical composition and ion exchange capacity (IEC). The selectivity order is Pb²⁺?>?Cu²⁺?>?Fe²⁺?>?Zn²⁺?>?Ni²⁺. Removal of metal ions from the aqueous solution and from effluents of a steel mill has been studied.     

Interaction between peat, humic acid and aqueous metal ions

Analysis of peat samples from four regions of the British Isles indicates that the concentrations of Al, Pb and common transition metals tend, as expected, to be higher in regions subject to industrial pollution, but that the concentrations of the nontransition metals Na, K, Mg, Ca and Zn tend to be higher in regions remote from industrial pollution. Humic acids were extracted from the most polluted and least polluted of the peat samples and some characteristics of these acids were compared with those of two commercial acids. Values for stability constants of complexes formed between humic acids extracted from peat and Cu²⁺, Zn²⁺ or Pb²⁺ have been obtained by an ionexchange equilibrium method. Of the three metal ions examined, Pb²⁺ was found to form the most stable humic acid complexes, followed by Cu²⁺: this order agrees with the findings of Irving and Williams and of Bunzl. Implications to the binding of actinide and other heavy metal ions in aqueous humic acid are discussed.     

Solid phase extraction of trace metals from environmental samples using Amberlite XAD-7 loaded with 2-hydroxy-propiophenone-4-phenyl-3-thiosemicarbazone and determination by inductively coupled plasma–atomic emission spectrometry

A method for the solid phase extraction of trace metals, namely Co, Cu, Pb, Ni and Zn, from environmental and biological samples using column Amberlite XAD-7 loaded with 2-hydroxy-propiophenone-4-phenyl-3-thiosemicarbazone (HPPPTSC) and determination by inductively coupled spectrometry (ICP–AES) has been developed. The reagent has the capacity to form chelate complexes with the metals because of three binding sites in the reagent molecule. The optimum experimental conditions for the quantitative sorption of five metals, pH, effect of flow rate, concentration of eluent, sorption capacity and the effect of diverse ions on the preconcentration of analytes have been investigated. The sorption capacity of the resin has 83, 127, 35, 88 and 85?µmol?g^?1 for Co²⁺, Cu²⁺, Pb²⁺, Ni²⁺ and Zn²⁺, respectively. The preconcentration factors for Co²⁺, Cu²⁺, Pb²⁺, Ni²⁺ and Zn²⁺ were 100, 110, 120, 140 and 150, respectively. The accuracy of the proposed procedure was evaluated by standard reference materials. The achieved results were in good agreement with certified values. The proposed method was applied for the determination of trace metals in river water and plant leaves.     

Trace Metals in Fish and Crustaceans - Identifying Heavier Polluted Areas in the Ghanaian Continental Shelf

Abstract

The concentrations of four trace metals, namely copper, lead, cadmium and manganese, were determined in six fish species and three crustaceans collected from five sites spanning over 70% of the Ghanaian coastline.

Copper and lead were determined in Barracuda (Spraena spraena), the Ribbon fish (Trichiurus lepturus), the Sardine (Sardinella spp), the Sole (Cynoflossus senegalensis), the Sea Bream (Pagrus coupei) and the Soldier fish (Cynapastas marmuratus). Cadmium and manganese were analyzed in the Blue Crab (Callinectes sepidus), the Spiny lobster (Panilirus regius) and the edible shrimp (Crago septempinosus). Sampling sites included Takoradi, Elmina, Cape Coast, Accra and Tema.

Lead and copper in the fishes ranged 0.25-0.94 μgg^?1 fresh weight and 0.40-2.54 μgg^?1 dry weight (FW) respectively whilst cadmium and manganese in the crustaceans ranged 0.05-0.083 μgg^?1 FW and 0.554-1.404 μgg^?1 FW respectively.

The Barracuda accumulated the greatest amount of metals whilst the sardine accumulated the least. with the crustaceans, there was a significant difference between the amounts of the metals accumulated. the blue crab accumulated the greatest and the edible shrimp the least.

The analysis showed that: (i) there was a positive correlation between the metals bioconcentrated and the extent of pollution of the marine waters and (ii) along the Ghanaian Continental Shelf, the extent of pollution was of the increasing order as: Elmina = Cape Coast < Takoradi < Accra < Tema. Pollution of the marine waters could be minimized by control of flow of pollutants from land based activities.     

Isolation and characterisation of cadmium-resistant bacteria from an industrially polluted coastal ecosystem on the southeast coast of India

A total of 35 bacterial strains were isolated from the industrially polluted Cuddalore coast, on the southeast coast of India. Of these, 17 strains were cadmium resistant and the remainder were sensitive. Six strains (C-1, C-8, C-10, C-12, C-14 and N-1) were selected based on high levels of cadmium tolerance (>150 mg L^?1) and were termed highly cadmium-resistant bacteria (HCRB). These HCRB were identified on the basis of morphological, biochemical and partial sequencing of their 16S rRNA genes. The antibiotic-susceptibility patterns and minimum inhibitory concentrations (MIC) of different metals (Cu²⁺, Pb²⁺ and Zn²⁺) against each HCRB were determined. Among the isolates, C-14 showed high degrees of metal and antibiotic resistance compared with other HCRB. Growth rates of HCRB at two different Cd²⁺ concentrations (50 and 100 mg L^?1) and under different metal conditions (Cd²⁺, Cu²⁺ and Pb²⁺) were also investigated. HCRB growth rates were lower in the metal-treated condition than in the untreated condition. Isolates C-14 and N-1 removed>80% of Cd²⁺ from cadmium-treated broth. However, isolate C-14 removed 92.3% of Cd²⁺ compared with 86.5% for isolate N-1. Bacteria showing residual growth rates under metal stress conditions might be useful in metal removal applications under growing conditions.     

Removal of heavy metals from aqueous solutions using activated carbon prepared from Cicer arietinum

Removal of Cu²⁺, Cd²⁺, Pb²⁺, and Zn²⁺ from aqueous solutions by activated carbon prepared from stems and seed hulls of Cicer arietinum, an agricultural solid waste, has been studied. The influence of various parameters, such as pH, contact time, adsorbent dose, and initial concentration of metal ions on removal was evaluated. The activated carbon was characterized by FT-IR spectroscopy, X-ray diffraction, and elemental analysis. Sorption isotherms were studied using Langmuir and Freundlich isotherm models. All experimental sorption data were fitted to the sorption models using nonlinear least-squares regression. The maximum adsorption capacity values for activated carbon prepared from Cicer arietinum waste for metal ions were 18 mg g^?1 (Cu²⁺), 18 mg g^?1 (Cd²⁺), 20 mg g^?1 (Pb²⁺), and 20 mg g^?1 (Zn²⁺), respectively. The Freundlich isotherm model fit was best, followed by the pseudo-second-order kinetic model. Desorption studies were carried out with dilute hydrochloric acid for quantitative recovery of the metal ions and for regeneration of the adsorbent.     

Acclimation and tolerance of Artemia salina and Ophryotrocha labronica to cooper sulphate

The brine shrimp Artemia salina L. and the polychaete worm Ophryotrocha labronica La Greca and Bacci were acclimated in sea water with copper sulphate at concentrations of 0.1, 0.05, and 0.025 ppm Cu⁺⁺, for 3 and 2 generations, respectively. Both adults and larvae of A. salina showed a greater tolerance to 1 ppm Cu⁺⁺ after acclimation compared to controls of the same age, although this tolerance diminished in successive generations. The acclimation effect was less marked in O. labronica. In both species, tolerance to 10 ppm Cu⁺⁺ upwards was not enhanced. Growth-rate inhibition and an adverse effect on reproduction was observed, in some instances in direct relationship to the acclimation concentration. It is suggested that, in A. salina, a certain tolerance to copper may be acquired through exposure to low concentrations.     

细颗粒物(PM_(2.5))主要组分模拟溶液对发光细菌的光抑制分析

为明确NH_4~+、 NO_3~-、SO_4~(2-)及金属等组分在水溶性提取液对发光细菌的光抑制过程中所起的作用,参照PM_(2.5)样品提取液浓度,模拟配制与3级以上PM_(2.5)样品提取液中主要组分:硫酸盐、硝酸盐、氨盐相同浓度的溶液,同时选取与PM_(2.5)可溶性提取液发光抑制率相关性较强的铅、锌,配制不同浓度级别模拟溶液,测试各单一组分对发光细菌的发光抑制率及其混合溶液对发光细菌的联合影响效应。基于毒性单位法(TU)、相加指数法(AI)和混合毒性指数法(MTI)评价了混合体系联合影响的作用类型。结果表明,与3~6级PM_(2.5)可溶性提取液中硫酸氨、硫酸氢氨、硝酸氨、硫酸锌和硝酸铅浓度相同的模拟溶液对发光细菌的发光没有抑制作用。不同的评价方法对PM_(2.5)主要组分混合体系联合效应评价结果具有较好的一致性,硫酸氨、硝酸氨、硫酸氢氨混合溶液中,对发光细菌的光抑制均为硫酸氢氨的独立作用,硫酸锌与硝酸铅的混合体系,锌和铅对发光细菌的联合影响效应表现为协同,硫酸氨、硝酸氨、硫酸氢氨与硫酸锌、硝酸铅的多元混合体系呈现协同作用。     

Capacity of simultaneous removal of zinc and cadmium from contaminated media, by two microalgae isolated from a polluted site

Several aquatic environments have been contaminated with heavy metals dumped via industrial effluents. Numerous studies have been published regarding the removal of single metals from aqueous solutions by microalgal biomass. However, such studies do not reflect the actual problem associated with industrial effluents because usually more than one metal species is present. Here we studied the biosorption capacity of Zn²⁺ and Cd²⁺ as single- and binary-metal systems by two microalgae, Scenedesmus obliquus and Desmodesmus pleiomorphus, isolated from a polluted site in Northern Portugal. For each metal independently, D. pleiomorphus showed a higher metal sorption capacity than S. obliquus, at concentrations ranging from 60 to 300 mg/l (except 150 mg_Cd/l). Maximum amounts of Zn²⁺ and Cd²⁺ removed were 22.3 and 60.8 mg/g by S. obliquus, and 83.1 and 58.6 mg/g by D. pleiomorphus. In binary-metal solutions, S. obliquus was in general able to remove Zn²⁺ to higher extents than Cd²⁺, whereas the opposite was observed with D. pleiomorphus. The simultaneous uptake of Zn²⁺ and Cd²⁺ by both microalgae was considerably lower than that of their single-metal counterparts, at equivalent concentrations. Although microalgal uptake from binary-metal solutions was lower than from single-metal ones, the wild microalgae selected were able to efficiently take up mixtures of Zn²⁺ and Cd²⁺ up to 300 mg/l of both metals—thus materializing a promising bioremediation vector for polluted waters.