The Application of Adsorption Modeling and Fourier Transform Infrared Spectroscopy to the Comparison of Two Species of Plant Growth–Promoting Rhizobacteria as Biosorbents of Cadmium in Different pH Solutions

Batch experiments were performed to determine the cadmium absorption capacity of two plant growth–promoting rhizobacteria at different pH levels and in different cadmium concentrations. Comparison of the mean metal removal from two species of bacteria studied showed that Pseudomonas florescence is the superior species for removing cadmium at all cadmium concentrations. The maximum cadmium absorption by P. florescence and P. putida were at 5 mg/L of cadmium concentration in pH 6 and 7, respectively. The applicability of the Langmuir and Freundlich isotherm models was surveyed. Comparison of two isotherm parameters (Q _m and a) further confirmed that P. fluorescence was better at binding cadmium ions (52.6 and 7.7 mg/g, respectively). Adsorption reaction also was considered by Fourier transform infrared (FTIR) spectroscopy. The FTIR analysis implied that the principal functional sites in the bacterial cell walls were phosphoryl and hydroxyl, carboxyl, amide I, amide II, and amine groups.     

Growth and Heavy Metal Binding Properties of Transgenic Chlamydomonas Expressing a Foreign Metallothionein Gene

We have compared the growth rates and cadmium binding capacity of wild-type and transgenic Chlamydomonas reinhardtii cells expressing a foreign class-II metallothionein. We observed that cells expressing metallothionein grew to significantly higher cell densities than wild-type cells in the presence of a toxic cadmium concentration (40 μM). When grown at a low (5 μM) cadmium concentration, cells expressing metallothionein bound twofold more cadmium (0.43 μg Cd)mg Ch1) than wild-type. At cadmium concentrations (40 μM), which induce phytochelatin synthesis in wild-type cells the cadmium binding capacity of both wild-type (79.6 μg Cd)mg Ch1) and transformed cells (86.4 μg Cd)mg Ch1) was similar; however, the transformed cells grew to higher densities than the wild type. These results suggest that under conditions that apparently induce phytochelatin expression, the presence of metallothionein in the cytoplasm reduces heavy metal toxicity. Furthermore, because cells expressing metallothionein grow to higher densities than wild-type cells at a toxic cadmium concentration (40 μM), the transgenic cells sequester more total cadmium (9% of total Cd) from the medium than the wild type (5.5% of total Cd). These results indicate that the trace-metal binding properties of Chlamydomonas can be enhanced through the expression of trace-metal-specific binding proteins.     

Concentrations of cadmium,lead, selenium,and zinc in human blood and seminal plasma

The concentrations of cadmium, lead, selenium, and zinc in blood and seminal plasma were determined in 76 Singapore males. Except for zinc, the concentrations were generally higher in blood than in seminal plasma (cadmium, 1.31 μg/L vs 0.61 μg/L; lead, 82.6 μg/L vs 12.4 μg/L, and selenium, 163.6 μg/L vs 71.5 μg/L). The mean concentration of zinc in seminal plasma was more than 30 times higher than in blood (202 mg/L vs 6.2 mg/L). Significant positive correlations were found between the concentrations in blood and seminal plasma for the two essential trace elements: selenium (r=0.45,p<0.001) and zinc (r=0.25,p<0.05). However, no relationships were found between the concentrations in blood and seminal plasma for two toxic metals (cadmium and lead). Significant inverse correlations were observed between Cd and Zn (r=−0.40,p<0.01), and Pb and Se (r=−0.32,p<0.05) in blood, whereas significant positive correlations were noted between Cd and Se (r=0.45,p<0.01), Cd and Zn (r=0.35,p<0.05), and Se and Zn (r=0.57,p<0.001) in seminal plasma. The physiological significance of these relationships are also discussed in this paper.     

Cadmium biosorption by <Emphasis Type="Italic">Bacillus</Emphasis><Emphasis Type="Italic"> circulans</Emphasis> strain EB1

Summary A heavy metal resistant bacterium, Bacillus circulans strain EB1 showed a high cadmium biosorption capacity coupled with a high tolerance to this metal when grown in its presence. Bacillus circulans EB1 cells grown in the presence of 28.1 mg cadmium/l were capable of removing cadmium with a specific biosorption capacity of 5.8 mg Cd/g dry wt biomass in the first 8 h. When the cells were pre-conditioned with low concentrations of cadmium in pre-grown medium, the uptake was increased to 6.7 mg Cd/g dry wt biomass. The maximum uptake of␣cadmium was during mid-logarithmic phase of growth. The resting cells (both wet and dry) of EB1 were also able to biosorb cadmium. Specific biosorption capacities of wet and dry biomass were 9.8 and 26.5 mg Cd/g dry wt biomass, respectively. Maximum cadmium removals by both wet and dry cells were at pH 7.0. The results showed that the cadmium removal capacity of resting cells was markedly higher than that of growing cells. Since both growing and resting cells had a high biosorption capacity for cadmium, EB1 cells could serve as an excellent biosorbent for removal of cadmium from natural environments.     

In vivo neutron activation analysis of organ cadmium burdens

In vivo neutron activation measurements of liver and kidney cadmium have been mae in 77 exposed workers and 101 referents. Cadmium levels were higher in exposed workers than in referents; both in liver, 25.7 cf. 0.6 μg/g, and kidney, 17.9 cf. 2.7 mg. The 19 referents who never smoked had lower mean organ cadmium burdens than the other referents, the difference achieving statistical significance in the kidney,p<.01. Cigaret smoking was estimated to increase cadmium body burden by 370-140 μg/pack year. These referent cadmium levels are similar to, although slightly below, previous in vivo and autopsy data.

     

The mechanism of cadmium removal from aqueous solution by nonmetabolizing free and immobilized live biomass of Rhizopus oligosporus

A preliminary study on the removal of cadmium by nonmetabolizing live biomass of Rhizopus oligosporus from aqueous solution is presented. The equilibrium of the process was in all cases well described by the Langmuir sorption isotherm, suggesting that the process was a chemical, equilibrated and saturable mechanism which reflected the predominantly site-specific mechanism on the cell surface. A curve of Scatchard transformation plots reflected the covalent nature of Cd²⁺ adsorption by the cells. The maximum cadmium uptake capacities were 34.25 mg/g for immobilized cells and 17.09 mg/g for free cells. Some factorial experiments in shake flasks were performed in order to investigate the effect of different initial cadmium concentrations and biomass concentrations on the equilibrium. Experimental results showed a reverse trend of the influence of the immobilized and free biomass concentration on the cadmium specific uptake capacity. The immobilized cells had a higher specific cadmium uptake capacity with increasing biomass concentrations compared to free cells. In a bioreactor, the cadmium uptake capacity of immobilized cells (q_max = 30.1–37.5 mg/g) was similar to that observed in shake flask experiments (q_max = 34.25 mg/g) whereas with free cells the bioreactor q_max of 4.8–13.0 mg/g; was much lower than in shake flasks (q_max = 17.09 mg/g), suggesting that cadmium biosorption by immobilized cells of R. oligosporus might be further improved in bigger reactors. EDAX and transmission electron microscopic experiments on the fungal biomass indicated that the presence of Cd²⁺ sequestrated to the cell wall was due to bioadsorption.     

Cadmium Removal by Lemna minor and Spirodela polyrhiza

The present study investigates the ability of two genus of duckweed (Lemna minor and Spirodela polyrhiza) to phytoremediate cadmium from aqueous solution. Duckweed was exposed to six different cadmium concentrations, such as, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mg/L and the experiment was continued for 22 days. Water samples were collected periodically for estimation of residual cadmium content in aqueous solution. At the end of treatment period plant samples were collected and accumulated cadmium content was measured. Cadmium toxicity was observed through relative growth factor and changes in chlorophyll content. Experimental results showed that Lemna minor and Spirodela polyrhiza were capable of removing 42–78% and 52–75% cadmium from media depending upon initial cadmium concentrations. Cadmium was removed following pseudo second order kinetic model. Maximum cadmium accumulation in Lemna minor was 4734.56 mg/kg at 2 mg/L initial cadmium concentration and 7711.00 mg/kg in Spirodela polyrhiza at 3 mg/L initial cadmium concentration at the end of treatment period. Conversely in both cases maximum bio-concentration factor obtained at lowest initial cadmium concentrations, i.e., 0.5 mg/L, were 3295.61 and 4752.00 for Lemna minor and Spirodela polyrhiza respectively. The present study revealed that both Lemna minor and Spirodela polyrhiza was potential cadmium accumulator.     

Purification and Characterization of Cadmium-Binding Protein from Unicelluar Alga Chlorella sorokinian

The unicellular green alga Chlorella sorokiniana ANA9 is highly resistant to heavy metals, and its metal-binding proteins are induced in the presence of cadmium. A novel cadmium-binding protein in C. sorokiniana cultured in 100 mg/l cadmium ions for 4 days was isolated and characterized. The crude protein extract was obtained by cell disruption and partly purified by ammonium sulfate precipitation. After purification by anion-exchange chromatography with diethylaminoethyl (DEAE)-Sepharose CL-6B, the protein was further purified by gel filtration with Sephacryl S-100, followed by Sephadex G-75. The molecular weight of the purified protein was determined to be 11.5 kDa by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. The cadmium binding capacity of the purified protein was 119 μg/mg. The involvement of thiol coordination in metal-ion binding was confirmed by measuring the ultraviolet spectrum. This article is the first to describe the metallothionein-like cadmium-binding protein from Chlorella species, the expression of which is induced by cadmium exposure.     

秋华柳和枫杨幼苗对镉的积累和耐受性

以秋华柳和枫杨当年实生幼苗为研究对象,采用向土壤添加外源镉(CdCl₂ · 2.5H₂O)的形式设置了0(对照组)、10 、20 、50、100 mg/kg 5个处理,研究了镉胁迫下秋华柳和枫杨幼苗的生长、生物量变化和根茎叶镉含量,并评价了两树种的耐性指数(Ti)、转移系数(Tf)和生物富集系数(BCF)。结果表明:(1)在镉含量为10 mg/kg时,秋华柳和枫杨幼苗基于生长和生物量参数的耐性指数(Ti)分别为91.72和91.62,与对照组相比无显著变化,其余各组(20、50、100 mg/kg)则显著低于对照植株(P<0.05);(2) 土壤镉浓度小于20mg/kg时,秋华柳植株茎、叶镉积累量分别高达61.73 mg/kg、163.04 mg/kg,根镉积累量为91.05 mg/kg;枫杨植株茎、叶镉积累量最高分别为7.9 mg/kg、5.25 mg/kg,仅为秋华柳茎、叶的12.8%和3.2%,根镉积累量高达190.68 mg/kg;(3) 除对照外,秋华柳幼苗各部分镉含量为叶＞根＞茎,转移系数(Tf)介于0.789-1.513之间,枫杨幼苗各部分镉含量为根＞茎＞叶,转移系数(Tf)介于0.037-0.044之间,远远小于秋华柳Tf;(4)秋华柳和枫杨幼苗在土壤镉浓度为10 mg/kg时具有很高的生长适应性和耐性,秋华柳根吸收的镉向地上部分转移能力、地上部分积累镉的能力都远远大于枫杨,生物富集系数(BCF)进一步证实了这一特性。研究证明,秋华柳植株具有很高的镉耐性、镉转移能力及地上部分积累镉的能力,适合于镉污染严重区域的植物修复。     

Effects of Cadmium on the Metabolic Activity of Avena sativa Plants Grown in Soil or Hydroponic Culture

Oat (Avena sativa L.) plants cultured in soil and hydroponic culture were treated with cadmium [0.154 mg g^–1 (dry soil) and 100 M CdSO₄, respectively] for 21 d and growth rate and various biochemical processes were studied. Applied cadmium reduced plant growth and chlorophyll content. Changes in activity of enzymes involved in C, N and S metabolism and in guaiacol peroxidase activity were observed. In particular, O-acetylserine sulphydrylase (OASS; EC 4.2.99.8) activity was increased by Cd exposure in both growth conditions, probably as a resistance mechanism to cadmium based on the production of phytochelatins. Results show that both field and hydroponic conditions represent suitable systems for investigating Cd effects on plant growth and metabolism.     

Using tree leaves and barks collected from contaminated and uncontaminated areas as indicators of air metallic pollution

Abstract

The aim of this study was to show the usefulness of woody species in assessing air pollution by cadmium, copper, lead, and zinc. For this, washed leaves, unwashed leaves, and barks of a coniferous species (Cupressus sempervirens var. fastigiata) and a broadleaved one (Eucalyptus cladocalyx F. Muell) were analyzed for cadmium, copper, lead and zinc contents. A transect sampling approach was carried out during spring 2016. Fifty stations were selected along an intensive traffic road, and three in a control area. The results showed that the highest concentrations were recorded in barks for copper (21.86?µg/g, 23.33?µg/g) and lead (14.53?µg/g, 63.33?µg/g), and in unwashed leaves for cadmium (0.57?µg/g, 1.19?µg/g) and zinc (48.94?µg/g, 47.6?µg/g) for E. cladocalyx F. Muell, and C. sempervirens var. fastigiata, respectively. Lead and zinc are the most accumulated metals compared to cadmium and copper in all samples. The studied metal contents in urban area were significantly higher than that of the control one. This represents that traffic road has influenced the metals contamination of the surrounding area. Results of the bioconcentration factor (BCF) for both species indicate that the studied species could be used as biomonitors to identify ecological problems and to predict effect on wildlife habitats. The highest values of metal accumulation index (MAI) indicate the effectiveness of these trees for controlling the air metals in the polluted areas. Result shows too that the studied species could be used for phytoextraction of heavy metals from the polluted soils and/or air.     

两株多环芳烃降解菌协同对菲-镉污染的去除特性北大核心

【目的】从污染土壤中分离筛选一株多环芳烃降解菌,并探究其与Pseudomonas aeruginosa B6-2构建的混菌体系对菲-镉复合污染的修复效能,以及微生物代谢特性对不同镉浓度赋存的响应特性,以期为复合污染的生物修复提供优良菌株资源及应用技术参考。【方法】采用富集驯化、筛选纯化方法得到一株多环芳烃降解菌,通过生理生化特征和16S rRNA基因序列分析进行鉴定。利用高效液相色谱法和电感耦合等离子体质谱法评估不同镉浓度赋存下各反应体系对菲和镉的去除效能;通过菌体细胞形态的扫描电镜观测及菌株代谢活性检测,探讨镉胁迫对菲生物降解过程的影响机制。【结果】筛选得到一株具有重金属耐受性和多环芳烃高效降解菌SZ-3,经鉴定为节杆菌属;降解菌协同体系(M)具有良好的菲降解效能和抗镉胁迫优势。镉胁迫浓度为0.5、10 mg/L时,M对菲和镉的去除率分别高于85%、80%;镉胁迫浓度为25、50 mg/L时,2种污染物的去除率均大于65%。扫描电镜分析表明,镉胁迫导致菌体表面粗糙且出现不同程度变形,菌体间黏附性和聚集性提高。反应周期内,邻苯二酚1,2-双加氧酶活性与电子传递体系活性随镉浓度增加而降低,两者变化与菲降解速率变化一致。【结论】Arthrobacter sp.SZ-3是一株PAHs高效降解菌,能与Pseudomonas aeruginosa B6-2协同高效修复菲-镉复合污染,随着初始镉胁迫浓度增加,混菌协同对目标污染物去除的优势显著。     

干旱胁迫下镉处理对互叶醉鱼草幼苗生长、镉积累及光合生理的影响

为探究干旱条件下,互叶醉鱼草(Buddleja alternifolia Maxim.)幼苗对重金属镉胁迫的生长及光合生理响应机制,以两年生互叶醉鱼草幼苗为试验材料,设置对照与干旱两个水分处理组(土壤相对含水率分别为:65%—60%,35%—30%),每个水分处理条件下再分别设置3个镉处理浓度(0.28、(0.6+0.28)、(1.2+0.28)mg/kg),共6个处理。测定不同水分及镉处理对互叶醉鱼草生长、生物量、光合参数及体内重金属含量的影响。结果表明:干旱与镉复合胁迫下植物的存活率为100%。镉胁迫、干旱与镉复合胁迫均不同程度抑制了互叶醉鱼草幼苗生长、生物量积累、植株的光合作用及叶绿素含量,且其光合和叶绿素含量的降幅明显大于单一镉胁迫。镉胁迫下,互叶醉鱼草幼苗单株最高镉富集量为69.33 mg/kg,而复合胁迫下单株最高镉富集量为50.68 mg/kg。以上结果表明:干旱胁迫能够加重镉胁迫对植物的影响,使复合胁迫下互叶醉鱼草生长、光合生理及镉富集能力下降。但单一镉胁迫下,互叶醉鱼草对镉具有更强的耐受性,并有较高的生物富集能力,且干旱与Cd复合胁迫下互叶醉鱼草幼苗仍有一定的镉积累量。因此在干旱半干旱区园林绿化以及Cd污染地区的生态建设中,互叶醉鱼草是一种具有巨大应用潜力和前景的灌木树种。     

Compartmentation of Cadmium and Iron in Mesembryanthemum crystallinum Plants during the Adaptation to Cadmium Stress

The common ice plants (Mesembryanthemum crystallinum) at the stage of five leaf pairs were exposed to cadmium chloride solutions (1, 0.1, and 0.01 mM) under the conditions of water culture. After five days, the partition of cadmium and iron in the plant organs and in the cell structures of the apical root region were investigated. Plant adaptation to excess cadmium in the environment was assessed by an increase in the leaf and root weight, a change in peroxidase activity, and an accumulation of proline. The common ice plant accumulated cadmium mainly in the root system. At a high concentration of cadmium in the nutrient solution (1 mM), its content in the root exceeded 2 g/kg fr wt, while at a concentration of 0.01 mM, it was as low as 10 mg/kg. Dithizone staining of transverse sections of the root apical region showed that, after a 48-h-long exposure of plants to 0.1 mM cadmium chloride, cadmium was localized in the cell walls of endodermis and metaxylem. The level of cadmium in leaves varied from 0.5 to 18 mg/kg fr wt. However, there was only a weak correlation between cadmium accumulation and the extent of a biomass decrease in the leaves of various stories, when cadmium concentration in the medium (1 mM cadmium chloride) was toxic. This fact could be related to a marked efflux of endogenous iron from old leaves into the young ones and to a change in the cadmium/iron ratio in the tissues. Proline accumulation in the third leaf pair and in the roots occurred at a relatively low cadmium content (10–12 mg/kg fr wt) in these organs. Maxima of activity of all three forms of peroxidase, viz., soluble, ionically-bound, and covalently-bound peroxidases, in roots were found at a high accumulation of cadmium in these organs (45 mg/kg fr wt). These maxima exceeded 3–4-fold the activity in aging leaves containing 5 mg cadmium/kg fr wt. A decrease in peroxidase activity in leaves was accompanied by a 3.3-fold decrease in iron content; thus, it could be caused by a deficiency of available iron necessary for the enzyme functioning. It was concluded that the resistance of Mesembryanthemum crystallinum, a halophyte, to excess cadmium content in the medium was achieved by its predominant accumulation in roots, where excess cadmium is compartmentalized in the apoplast and seems to be subjected to detoxification through pectate formation. Moreover, the leaves and, particularly, the roots are characterized by a high activity of the antioxidant systems, such as guaiacol-dependent peroxidases, and an occurrence of proline at modest cadmium concentrations.     

Effects of Artichoke Extract Supplementation on Gonads of Cadmium-Treated Rats

The present study was designed to determine whether artichoke (Cynara scolymus) exerts a protective effect on gonads of cadmium-treated rats and if there is a relationship between artichoke supplementation and nitric oxide (NO) formation in cells. Forty Wistar albino male rats, weighing an average of 90 g each, were equally divided into four groups receiving 1 mg/100 g cadmium chloride by injection (group 1), the same dose CdCl₂ plus 3 mg/100 g artichoke extract (group 2), the same dose of artichoke extract (group 3), and male controls (group 4). Four additional groups, labeled 5–8, consisted of identically treated and control female rats. After 4 weeks of treatment, the animals were killed and their gonads were removed for histological examination. As expected, the seminiferous tubules and Leydig cells were damaged by cadmium. Ovarian tissue was not damaged to the same extent as testicular cells. Artichoke extract exerted a clear protective effect against Cd-induced testicular damage and lowered NO production to the same level of that in the control groups.     

Effect of cadmium on lipid peroxidation and activities of antioxidant enzymes in growing pigs

Malondialdehyde (MDA), glutathione (GSH) content, total antioxidant capacity (T-AOC) levels, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and glutathione transferase (GST) activities were studied in serum, liver, and kidney of growing pigs after graded doses of cadmium administration in diets. One hundred ninety-two barrows (Duroc x Landrace x Yorkshire), with similar initial body weight 27.67±1.33 kg, were randomly allotted into 4 different treatments with 3 replications (16 pigs per replication). The treatments received the same basal diet added with 0, 0.5, 5.0, and 10.0 mg/kg cadmium (as CdCl₂), respectively. The results showed pigs treated with 10 mg/kg cadmium significantly decreased average daily gain (ADG) (p<0.05) and increased feed/gain ratio (F/G) (p<0.05) compared to the control. In this treatment, the contents of MDA increased significantly (p<0.05), GSH concentrations, T-AOC levels, and the activities of SOD, GSH-PX, and GST decreased significantly (p<0.05). The results indicate 10 mg/kg cadmium could decrease pig antioxidant capacity after extended exposure and cadmium-induced increase lipid peroxidation might not be only the result of the possibility of lower level of GSH but could also be as a result of direct action of cadmium on peroxidation reaction.     

Cadmium,cobalt, chromium,and experimental myocardial infarction

In the case of experimental heart muscle infarction, the infarcted tissue of 18 pigs had a cadmium content of 0.38 μg/g dry weight and a cobalt content of 0.45 μg/g dry weight. In 25 non-infarcted pig hearts, the cadmium concentration amounted to 0.27 μg/g dry weight and the cobalt concentration to 0.37 μg/g dry weight. Thus, as far as the infarcted heart muscle tissue is concerned, there is a highly significant increase in the cadmium content (p<0.01) and a significant increase in cobalt content (p<0.05) compared to a non-infarcted heart. No differences were established with regard to chromium concentrations.     

Simultaneous cadmium removal and 2,4-dichlorophenol degradation from aqueous solutions by Phanerochaete chrysosporium

Phanerochaete chrysosporium has been recognised as an effective bioremediation agent due to its unique degradation to xenobiotic and biosorption ability to heavy metals. However, few studies have focused on the simultaneous removal of heavy metals and organic pollutants. The aim of this work was to study the feasibility of simultaneous cadmium removal and 2,4-dichlorophenol (2,4-DCP) degradation in P. chrysosporium liquid cultures. The removal efficiencies were pH dependent and the maximum removal efficiencies were observed at pH 6.5 under an initial cadmium concentration of 5 mg/L and an initial 2,4-DCP concentration of 20 mg/L. The removal efficiencies for cadmium and 2,4-DCP reached 63.62% and 83.90%, respectively, under the optimum conditions. The high production levels of lignin peroxidase (7.35 U/mL) and manganese peroxidase (8.30 U/mL) resulted in an increase in 2,4-DCP degradation. The protein content decreased with increasing cadmium concentration. The surface characteristics and functional groups of the biomass were studied by scanning electron microscopy and a Fourier-transformed infrared spectrometer. The results showed that the use of P. chrysosporium is promising for the simultaneous removal of cadmium and 2,4-DCP from liquid media.     

Zinc,cadmium, mercury and selenium in minke whales,belugas and narwhals from West Greenland

Summary Samples of muscle, liver and kidney from 24 minke whales (Balaenoptera acutorostrata), 43 belugas (Delphinapterus leucas), and 98 narwhals (Monodon monoceros) were analyzed for zinc, cadmium, mercury, and selenium. Highly significant age accumulation of mercury was found. A lower level of significance of age accumulation of cadmium in belugas and narwhals is probably due to the fact that some of the highest cadmium concentrations are in subadults and young adults. The maximum concentrations of cadmium and mercury are very high: 1.68, 73.7, and 125 g cadmium, and 9.88, 42.8, and 4.61 g mercury per g wet weight of narwhal muscle, liver and kidney, respectively. The cadmium concentrations are correlated in the three organs, as are mercury and to a lesser extent selenium concentrations. The concentrations of mercury and selenium in liver are highly correlated.