强抗镉蜡状芽孢杆菌的分离鉴定及其抗性机理

从北京市远郊东三岔地区废弃的铅锌尾矿中筛选到1株强抗镉的细菌.通过细菌形态学观察、扫描电镜、X射线衍射能谱分析、甲基乙酰甲醇试验与酪氨酸水解试验等特征生理生化试验、菌株“G＋C mol%”值以及16S rDNA扩增与序列测定,鉴定此菌株为蜡状芽孢杆菌（Bacillus cereus）.分离菌株可以在镉浓度为1?000 mg/L的固体培养基平板上生长,表明菌株具有强抗镉的能力.进一步分析了菌株在添加Cd²⁺与未添加Cd²⁺的液体培养基中的生长曲线,并通过质粒消除试验证明该菌株的抗镉性质与抗性质粒的存在有关.     

硝基还原假单胞菌吸附重金属镉的机理研究

系统研究了硝基还原假单胞菌对重金属镉的吸附特性与吸附机理.研究结果表明,此株菌可以耐受200mg/L重金属镉,而进一步提高镉离子的浓度则会显著抑制该菌的生长.将该菌株接种至含20、50和100mg/L Cd~(2+)的液体LB培养基中,经过120h的培养,镉的去除率分别能达到94.3%,91.0%和86.0%.系统研究了pH值、温度、盐浓度和多种重金属离子存在下,该菌株对溶液中镉离子去除效果的影响.结果表明,硝基还原假单胞菌可以在pH值为4~8范围内有效吸附镉离子,当NaCl溶液提升至1mol/L时,该菌株仍可耐受,并且可以吸附除了铅离子之外的多种重金属离子.X射线光电子能谱分析结果显示,吸附后Cd~(2+)的结合能发生了变化.扫描电镜结果显示,与正常菌株相比,吸附镉的菌株产生明显形变,且表面有白色颗粒状物质吸附,结合X射线光电子能谱分析结果,可以说明生物矿化是该菌株吸附和钝化重金属的途径之一.     

海洋耐镉微生物筛选及其生物学特性

从重金属污染的近海域筛选到一株对镉具有较强抗性和富集能力的微生物Cd20002,该菌株在液体培养基中的最大耐受浓度为1 000 mg/L,在镉浓度达到200 mg/L时,其吸附率高达93.4%,根据形态特征和生理生化鉴定及16S rRNA测序鉴定为蓝杆菌。通过在不同的镉浓度环境对蓝杆菌Cd20002进行培养,测定其生长曲线,并优化菌体生长的条件及其吸附能力。结果表明,蓝杆菌Cd20002既能在重金属镉环境中生存,且富镉能力较强,对水产环境中重金属的生物清排具有重要意义。     

一株抗镉真菌的分离鉴定及特性研究

从矿区中分离到一株抗镉较强的真菌,对其进行鉴定,并检测了菌株对多种重金属的耐受性,不同镉浓度对菌株生长的影响及对镉的吸附特性。经鉴定该菌株为淡紫拟青霉菌(Paecilomyces lilacinus),命名为LLC4。菌株对Cd~(2+)的耐受浓度达268 mmol/L,对其他几种重金属的耐受性大小为:Zn~(2+)>Cu~(2+)>Mn~(2+)>Co~(2+);低浓度的Cd~(2+)对菌株的生长有促进作用,高浓度Cd~(2+)会抑制其生长;该菌株在不同Cd~(2+)浓度中对Cd~(2+)的吸附能力不同,当初始Cd~(2+)浓度为5 mmol/L时,最大的吸附率为100%,20 mmol/L时最大吸附量为12.19 mg/g。     

耐镉菌株的分离及其对Cd2+的吸附富集

采用梯度浓度驯化的方法,筛选分离出一株能高度耐镉和富集镉的菌株,初步鉴定为假单胞菌属(Pseudomonas sp.).该菌株在含Cd2+浓度4500mg/L的液体细菌培养基中能够生存,当Cd2+浓度为100mg/L时,pH值为6～8有利于提高菌株耐镉能力.Cd2+为低浓度时菌株积累Cd2+,菌体对Cd2+浓度为100mg/L的积累率达99.1%,冻干菌体对Cd2+的吸附量为8.786mg/g干菌体;当Cd2+浓度大于909mg/L时,菌体表现出外排Cd2+现象.红外分析和电镜观察表明,菌株细胞壁在吸附Cd2+中起重要作用,67.4%的Cd2+吸附在细胞壁上.     

模拟城市径流中加乐麝香和镉对大型水蚤的毒性效应

通过生物测试,研究了加乐麝香和重金属镉在模拟城市径流和清水条件下对大型水蚤(Daphnia magna)的单一、联合毒性效应.结果表明,在单一毒性效应试验中,当暴露时间为24,48h时,加乐麝香和镉在模拟城市径流条件下的EC50值分别为2.455,1.187mg/L以及0.384,0.304mg/L;在清水试验条件下的EC50值分别为0.533,0.189mg/L以及0.359,0.244mg/L.2种污染物在模拟城市径流条件下EC50值均高于清水条件下的EC50值.采用毒性1∶1试验测定2种污染物联合毒性效应,当暴露时间为24,48h时,在清水条件下AI>0,二者联合毒性效应表现为协同效应;在模拟城市径流条件下,AI<0,联合毒性效应为拮抗效应.     

球形红细菌转化去除重金属镉及其机理研究

研究了不同理化因素对光合细菌球形红细菌(Rhodobacter sphaeroides)H菌株生长和镉去除能力的影响.结果表明,该菌株的最佳生长和对镉的最佳去除条件为:pH=7.0,温度为30℃,好氧黑暗,接种量9%.在最佳条件下,镉的去除率可达85%以上.通过X射线衍射光谱分析,H菌株对镉离子的转化产物为硫化镉.通过测定镉的去除与细菌生长曲线及半胱氨酸脱巯基酶的活性,表明镉的去除与菌体的生长稳定期相关.此外,通过分析菌体对硫酸盐的代谢过程,探讨了该菌株生长细胞去除重金属镉的机理.     

转枣树金属硫蛋白基因拟南芥对镉的耐受性研究

对转枣树金属硫蛋白(MT)基因拟南芥植株与非转基因对照组拟南芥对重金属镉的耐受性进行了研究,为实现用转基因生物法治理环境中重金属污染提供依据。采用水培实验,比较了转基因拟南芥与对照组拟南芥对镉的吸收情况。实验表明:经0.1 mol/L镉处理24 h和48 h时,转枣树MT基因拟南芥根部对镉的吸收量分别为22,323 mg/L,地上部分为513,667 mg/L,明显超过对照组(根部93,107 mg/L;地上部分323,437 mg/L);0.001 mol/L镉浓度处理下,转MT基因拟南芥对镉的富集系数为92.0%,而对照组仅为47.3%;转枣树MT基因拟南芥对镉的转移系数为1.053~3.473,因此转MT基因拟南芥属于镉超富集植物,转枣树MT基因显著地提高了拟南芥对重金属镉的耐受性。     

抗锶放线菌的分子鉴定及对Sr~(2+)的吸附效果和初步吸附机理分析

从大亚湾核电站附近水体中分离筛选出一株抗锶放线菌(编号YF-64),研究了该菌株在不同环境参数条件下对锶的吸附效果和初步机理,通过形态和16S rDNA序列相结合的方法对菌株进行了分类鉴定,采用红外光谱(FT-IR)分析技术对菌株吸附前后进行表征,探讨其吸附机制。结果表明,抗锶菌株隶属于天蓝黄链霉菌(基因序列登录号:JF901702),菌株对Sr~(2+)具有较强的吸附效果,根据数据显示,当接触时间为50 min,pH值为6,Sr~(2+)初始浓度为50 mg/L,摇床转速为120 r/min时,该菌株的吸附效果达到最佳为44.29 mg/g;FT-IR结果显示,JF901702菌株对Sr~(2+)的吸附主要是由细胞壁上的羟基,次甲基,羰基起主要吸附作用。由此可知,JF901702菌株可作为经济、高效、环境友好的生物吸附材料进行废水重金属处理。     

一株耐酸SRB的分离及其脱硫除镉性能

为减轻酸性矿山废水引起的环境污染,为矿山废水处理提供潜在的菌种资源,从土壤中分离出一株耐酸的硫酸盐还原菌SRB1并探讨了该菌株的还原硫酸盐和除镉特性.结果表明该菌株具有较强的脱硫除镉能力,其最低耐受pH值,最适温度,最大耐Cd²⁺浓度分别为3.7,35℃和40mg/L.在COD/SO₄^2-≥2,Cd²⁺浓度≤30mg/L条件下,除镉率可达99%以上.在高浓度Cd²⁺和SO₄^2-的体系中,该菌对Cd²⁺有较强的吸附作用,能将Cd²⁺从50mg/L降至15.5mg/L,吸附率达58%,采用二次培养能将SO₄^2-从1.5g/L降至0.04g/L,脱硫率达97.3%,Cd²⁺浓度几乎降为零.TEM、FTIR、SEM表征显示,在镉胁迫下,该菌株的细胞形态发生改变,吸附前后,红外吸收峰改变明显,沉淀颗粒含有结晶CdS.     

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil and model sorbents

Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.     

Degradation of metabolites accumulated of benzo[a]pyrene by coupling Penicillium Chrysogenum with KMnO4

Several main metabolites of benzo[a]pyrene （BaP） formed by Penicillium chrysogenum, Benzo[a]pyrene-1,6-quinone （BP 1,6- quinone）, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene （BP 7,8-diol）, 3-hydroxybenzo[a]pyrene （3-OHBP）, were identified by high-performance liquid chromatography （HPLC）. The three metabolites were liable to be accumulated and were hardly further metabolized because of their toxicity to microorganisms. However, their further degradation was essential for the complete degradation of BaP. To enhance their degradation, two methods, degradation by coupling Penicillium chrysogenum with KMnO4 and degradation only by Penicillium chrysogenum, were compared; Meanwhile, the parameters of degradation in the superior method were optimized. The results showed that （1） the method of coupling Penicillium chrysogenum with KMnO4 was better and was the first method to be used in the degradation of BaP and its metabolites; （2） the metabolite, BP 1,6-quinone was the most liable to be accumulated in pure cultures; （3） the effect of degradation was the best when the concentration of KMnO4 in the cultures was 0.01% （w/v）, concentration of the three compounds was 5 mg/L and pH was 6.2. Based on the experimental results, a novel concept with regard to the bioremediation of BaP-contaminated environment was discussed, considering the influence on environmental toxicity of the accumulated metabolites.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

Effects of two sludge application on fractionation and phytotoxicity of zinc and copper in the soil

The potential harm of heavy metals is a primary concern in application of sludge to the agricultural land. A pot experiment was conducted to evaluate the effect of two sludges on fractionation of Zn and Cu in soil and their phytotoxicity to pakchoi. The loamy soil was mixed with 0%, 20%, 40%, 60% and 80% (by weight) of digested sewage sludge (SS) and composted sludge (SC). The additions of both sludges caused a significant raise in all fractions, resulting in that exchangeable (EXCH) and organic bound (OM) became predominance of Zn and organic bound Cu occupied the largest portion. There was more available amount of Zn and Cu in SS treatments than SC treatments. During the pot experiment, the concentration of Zn in EXCH, carbonate (CAR) and OM and Cu in EXCH and OM fractions decreased in all treatments, so their bioavailability reduced. Germination rate and plant biomass decreased when the addition rate was high and the best yield appeared in 20% mixtures at the harvest of pakchoi. The two sludges increased tissue contents of Zn and Cu especially in the SS treatments. Zn in pakchoi was not only in relationship to ΔEXCH and ΔCAR forms but also in ΔOM forms in the sludge-soil mixtures. Tissue content of Cu in pakchoi grown on SC-soils could not be predicted by ΔEXCH. These correlation rates between Zn and Cu accumulation in pakchoi and variation of different fractions increased with time, which might indicate that sludges represented stronger impacts on the plant in long-term land application.     

Intraspecific differences in effects of co-contamination of cadmium and

A hydroponic experiment was carried out to study intraspecific differences in the effects of different concentrations of cadmium (Cd)(0-10 mg/L) and arsenate (As(V)) (0-8 mg/L) on the growth parameters and accumulation of Cd and As in six wheat varieties Jing-9428, Duokang-1, Jingdong-11, Jing-411, Jingdong-8 and Zhongmai-8. The endpoints of wheat seedlings, including seed germination,biomass, root length and shoot height, decreased with increasing the Cd and As concentrations. Significant differences in seed germination, biomass, root length, shoot height and the accumulation of Cd and As were observed between the treatments and among the varieties (p ＜ 0.05). The lethal dosage 50% were about 20, 80, 60, 60, 80 and 20 mg As/L for Jing-9428, Duokang-1, Jingdong-11,Jing-411, Jingdong-8 and Zhongmai-8, respectively, and the corresponding values for Cd were about 30, 80, 20, 40, 60 and 10 mg Cd/L, respectively. Among the six varieties, Duokang-1 was found to be the most resistant to Cd and As toxicity, and Zhongmai-8 was the most sensitive to Cd and As co-contamination. The resistance of the six varieties was found dependant on the seedling uptake of Cd and As. Duokang-1 was the most suitable for cultivation in Cd and As co-contaminated soils.     

Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture

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Isolation and preliminary characterization of a 3-chlorobenzoate degrading bacteria

A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several （halo）aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no （chloro）catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway.     

Single and joint effects of pesticides and mercury on soil urease

The influence of two pesticides including chlorimuron-ethyl and furadan and mercury （Hg） on urease activity in 4 soils （meadow burozem and phaeozem） was investigated. The soils were exposed to various concentrations of the two pesticides and Hg individually and simultaneously. Results showed that there was a close relationship between urease activity and organic matter content in soil. Chlorimuron-ethyl and furadan could both activate urease in the 4 soils. The maximum increment of urease activity by chlorimuronethyl was up to 14%-18%. There was almost an equal increase （up to 13%-21%） in the urease activity by furadan. On the contrary, Hg markedly inhibited soil urease activity. A logarithmic equation was used to describe the relationship （P〈0.05） between the concentration of Hg and the activity of soil urease in the 4 tested soils. Semi-effect dose （ED50） values by the stress of Hg based on the inhibition of soil urease in the 4 soils were 88, 5.5, 24 and 20 mg/kg, respectively, according to the calculation of the corresponding equations. The interactive effect of chlorimuron-ethyl or furadan with metal Hg on soil urease was mainly synergic at the highest tested concentrations.