Adsorption of Copper and Cadmium by Cu- and Cd-Resistant Bacteria and Their Composites with Soil Colloids and Kaolinite

Abstract

Remediation of toxic metals by bacteria offers a relatively inexpensive and efficient way for the decontamination of soil and associated environments. The present study was carried out to investigate the surface characteristics, adsorption, and remobilization of Cd and Cu on bacteria and their composites with soil colloidal components, which are the most active constituents in soils. The bacterial strain NTG-01 (Enterobacter aerogenes), which was both Cd- and Cu-resistant, was isolated from a heavily Cu-contaminated soil of the mining area in Daye suburb of Hubei Province, China. Batch laboratory experiments with NTG-01 and soil colloids were performed to quantify adsorption of Cu and Cd. The surface area of kaolinite and the soil colloids from an Alfisol and Ultisol increased by 3.0–8.8% after the introduction of the bacteria. In the presence of bacterial cells, the negative charges of soil colloid systems increased and the positive charges decreased, shifting pH from 4.0 to 6.5. Our results demonstrate that bacteria promote the adsorption of Cd and Cu by kaolinite and soil colloid systems. However, the heavy metals bound by the bacterial composites could also be easily released by NH₄NO₃ and EDTA. Caution should be taken when using such bacterial strains in bioremediation of heavy metal-contaminated soils.     

Effects of Temperature,pH and Salt Concentrations on the Adsorption of Bacillus subtilis on Soil Clay Minerals Investigated by Microcalorimetry

Adsorption of microorganisms on minerals is a ubiquitous interfacial phenomenon in soil. Knowledge of the extent and mechanisms of bacterial adsorption on minerals is of great agronomic and environmental importance. This study examined adsorption of Bacillus subtilis on three common minerals in soils such as kaolinite, montmorillonite and goethite under various environmental conditions. Isothermal titration calorimetry (ITC) was used to investigate the effects of temperature (20, 30, and 40°C), pH (5.0, 7.0, and 9.0) and KNO₃ concentration (0.001, 0.01, and 0.1 mol L^?1) on the adsorption by direct measurement of enthalpies. The results revealed that the adsorption process in all the mineral systems were exothermic, with the enthalpy changes (ΔH_ads ) ranging from ?52 to ?137, ?33 to ?147, and ?53 to ?141 kJ kg^?1 (dry weight of adsorbed bacteria) for kaolinite, montmorillonite, and goethite, respectively. No obvious dependence of ΔH_ads on temperature was observed. The heat release for all the systems generally declined with pH and decrease of salt concentration, which can be explained by the variations of hydrophobicity and electrostatic force with pH or salt concentration. The largest decrease was found for goethite among the three minerals from pH 5.0 to 7.0, suggesting that electrostatic attraction may play a more important role in bacterial adsorption on this mineral. The ΔH_ads values for all the minerals became nearly the same at pH 9.0, indicating that the same force probably hydrophobicity governing the adsorption for the minerals in alkaline environment. It is assumed that acidic or saline soils and the associated environments favor the adsorption of B. subtilis on clay minerals. In addition, the negative enthalpies expressed as kJ kg^?1 (carbon) revealed an energy flow into the environment accompanied by the carbon adsorption on the minerals in soil.     

Extremely Rapid Extraction of DNA from Bacteria and Yeasts

A very simple and rapid method for extracting genomic DNA from Gram-negative bacteria, Gram-positive bacteria and yeasts is presented. In this method, bacteria or yeasts are lysed directly by phenol and the supernatant is extracted with chloroform to remove traces of phenol. The supernatant contains DNA that is suitable for molecular analyses, such as PCR, restriction enzyme digestion and genomic library construction. This method is reproducible and simple for the routine DNA extraction from bacteria and yeasts.     

DNA微阵列技术在细菌感染后宿主反应研究中的应用

感染性疾病是病原微生物和宿主紧密相互作用的结果。深入理解宿主对病原微生物感染发生反应的分子基础是预防感染性疾病发生和组织损伤的必要条件。本文通过介绍体内、体外2种感染模型中宿主对细胞内和细胞外致病菌感染后的基因表达谱变化,简述了DNA微阵列技术在病原菌一宿主相互作用中宿主反应研究中的应用。     

细菌产生的挥发性物质及其生物学功能

细菌产生的挥发性物质种类繁多,成分复杂,是寻找具有特殊生物学功能的天然化合物的一个重要来源。近些年,越来越多的研究人员关注细菌产生的挥发性物质及其生物学功能。概述了细菌产生的挥发性物质的种类以及分析鉴定挥发性物质成分的方法;着重评述了细菌产生的挥发性物质对真菌、细菌、动物和植物生长和代谢的影响,并对细菌产生的挥发性物质未来的主要研究方向进行了展望。     

黏土矿物中重金属离子的吸附规律及竞争吸附

采用等温吸附法,研究了重金属铜、铅、镉、镍在膨润土中的吸附特征,发现膨润土对铜、铅的吸附明显强于镉、镍,吸附强度大小顺序为Pb2 >Cu2 >Ni2 >Cd2 。Langmuir和Freundlich方程对这4种金属离子等温吸附的拟合均呈极显著关系。Pb2 、Cd2 、Ni2 分别与Cu2 的双组分竞争吸附表明,黏土矿物对4种离子具有"选择性吸附"。在Pb2 、Ni2 、Cd2 的存在条件下,黏土矿物对Cu2 的吸附产生不同程度的下降;100mg/LCu2 对Pb2 的影响不大,但可完全抑制Ni2 、Cd2 的吸附。建立了IAS和LCA模型来预测Pb2 与Cu2 的双组分竞争吸附,并对LCA模型进行修正,提出了更符合实际情况的竞争吸附模型。文章最后用LCA修正模型对Pb2 与Cu2 的双组分竞争吸附进行了模拟。     

运用基因芯片技术建立检测水产食品中常见病原微生物方法的研究

目的:利用基因芯片技术,以细菌16S rDNA和23S rDNA为靶序列筛选引物和探针,建立快速、准确的检测水产食品中肠道致病菌的方法。方法:将致病菌的16S rDNA和23S rDNA全序列进行软件比对,在可变区和恒定区分别设计特异性寡核苷酸探针和通用性引物,点样于玻片制成基因芯片。致病菌DNA经过通用引物扩增后与芯片上的探针杂交,然后通过扫描图像对结果进行判断。对基因芯片检测的灵敏度进行了评价,并对模拟污染样本进行了实际检测,以验证所建立的方法。结果:设计的4对通用引物在同一条件下能够扩增7种常见肠道致病菌。在均一的杂交条件下能够同时检测单核细胞增生利斯特菌、副溶血性弧菌、霍乱弧菌、金黄色葡萄球菌、弗氏志贺氏菌、鼠伤寒沙门氏菌和肠出血性大肠杆菌O157∶H7;以鼠伤寒沙门氏菌为对象,本方法的检测灵敏度可达到10~3 cfu/mL,实际检测模拟污染的样本的正确率达到100%。结论:建立的基因芯片系统可以准确而稳定地实现对7种水产食品中常见致病菌的通用检测,为食源性感染的诊治与预防提供了有效的技术手段和方法依据。     

Calculations of DNA Condensation Caused by Ligand Adsorption

A method for calculating the curves of DNA transition from linear to condensed state upon binding of condensing ligands has been developed. The character of the transition and ligand concentration necessary for condensation have been shown to be governed by the length of DNA molecule, energy and stoichiometry parameters of the DNA–ligand complex (equilibrium constant between linear and condensed form in the absence of ligands, constants for ligand binding to linear and condensed forms, the number of base pairs covered by one ligand, etc.). The results of the calculations indicate that a slight difference in the free energies of these DNA states (less than 6 cal/mol(bp) for a DNA of 500 bp) is sufficient for the existence of a stable linear state in the absence of ligands (in free DNA) and the formation of stable condensed state upon complexation.     

Adhesion of Pseudomonas putida onto Palygorskite and Sepiolite Clay Minerals

Adhesion of bacteria to clay minerals is of great importance in both natural soil environments and technological applications. In the present study, equilibrium experiments along with Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy-dispersive X-ray analysis (EDX) were used to investigate the adhesion of Pseudomonas putida to the palygorskite and sepiolite clay minerals. The results showed that bacterial adhesion was rapid and reached equilibrium within 30 min. Equilibrium data showed that sepiolite has higher capacity and affinity than palygorskite for P. putida retention. Mixed FT-IR peak features of the clay minerals and P. putida were observed in the clay–bacteria complex spectra, indicating significant adhesion of P. putida to the minerals. However, some differences in the position of the individual bands were observed between infrared spectra obtained for pure bacteria or clay minerals and their corresponding clay–bacteria complexes, which are believed to be related to clay–bacteria interactions via different mechanisms. SEM/EDX analysis demonstrated fine fibrous clay particles adhered to the surface of individual P. putida cells. The results revealed rapid and close interactions of palygorskite and sepiolite with P. putida cells, which is important for better understanding the fate of bacteria in soil systems dominated by fibrous clay minerals and their practical applications in bioengineering and biotechnology.     

胆汁酸功能及其与肠道细菌相互关系

胆汁酸具有多种重要生理功能. 近年研究发现,胆汁酸可作为信号分子与褐色脂肪细胞表面受体TGR5结合,可激活法尼酯衍生物X受体（nuclear receptor farnesoid X receptor, FXR）的表达. 通过激活这些不同的信号传导途径,胆汁酸可以分别起到调节体内能量代谢平衡、控制肥胖以及抑制肠道细菌过度增殖的作用. 胆汁酸与人及动物肠道细菌具有复杂的相互关系：肠道细菌对于胆汁酸的转化很重要,除了在胆汁酸的转化中发挥重要作用外,肠道微生物菌群还可以十分有效地水解已被胆汁酸清除的生物体内结合寄生物或异源物质,促进这些物质的活化或肠肝循环. 宿主拥有一些抑制细菌过度增殖的机制,这些机制包括快速转运以及利用抗菌肽、蛋白水解肽和胆汁酸等进行抑菌;而有些肠道细菌在进化中形成一些抗性机制可避免胆汁酸胁迫. 本文主要就胆汁酸控制肥胖以及抑制细菌过度增殖的机制和胆汁酸与肠道细菌相互关系进行了综述.     

Adsorption of DNA on clay minerals: protection against DNaseI and influence on gene transfer

Abstract Numerous authors have investigated DNA relationships with sandy soil. A model composed of various DNAs adsorbed on montmorillonite clay was developed to assay enzyme (DNaseI) activity on clay-adsorbed nucleic acids. The extent of DNA adsorption was affected by the concentration and valency of the cations used (Mg²⁺, Ca²⁺, Na⁺), indicating a charge-dependent process. Calf thymus DNA was found to be highly adsorbed by smectite (up to 30 mg g⁻¹ of dry clay). Adsorbed DNA was shown to be more resistant to degradation by DNaseI than free DNA. Experimental data with plasmid and short linear amplified (through polymerase chain reaction) DNA showed that protection against nucleases was only partial. Nevertheless, clay-adsorbed DNA was found to be still able, even after a strong DNaseI treatment, to artificially transform competent Escherichia coli cells. The results show that persistance of DNA and gene transfer by genetic transformation may occur in soil.     

Isolation and Identification of Three Potassium-Solubilizing Bacteria from Rape Rhizospheric Soil and Their Effects on Ryegrass

More than 90% of potassium (K) in soil exists in forms of insoluble silicate minerals and cannot be directly utilized by plants. K-solubilizing bacteria (KSB) can improve soil fertility and plant growth as biofertilizers by decomposing silicate minerals and releasing insoluble K into soluble forms. The objectives of this study were to isolate and characterize KSB from rape rhizospheric soil and to evaluate their effects on ryegrass growth. In this study, 16 cultivable potential KSB were isolated from rape rhizosphere at first. Then, quantitative analysis revealed that three KSB strains, named S-15, S-17 and S-18, showed the best K mineral solubilizing ability and they were identified as Mesorhizobium sp., Paenibacillus sp. and Arthrobacter sp. Inoculating the three strains into available K limit soil increased available K content significantly. The result of the pot experiment revealed that the three strains increased ryegrass growth vigor, biomass yield and K uptake to different degrees in available K deficient soil. S-17 showed the most pronounced ryegrass growth promotion ability. Further studies are required to determine the effects of the three KSB on mobilization of K-bearing minerals under field conditions.     

Assays Based on Differential Adsorption of Single-stranded and Double-stranded DNA on Unfunctionalized Gold Nanoparticles in a Colloidal Suspension

Under certain conditions, single-stranded DNA adsorbs to negatively charged gold nanoparticles in a colloid whereas double-stranded DNA does not. We present evidence that this phenomenon can be explained by the difference in their electrostatic properties that in turn reflects conformational differences. The ability to discriminate the hybridization state of DNA on the basis of adsorption behavior can be utilized to design simple colorimetric and fluorimetric assays that take advantage of plasmon resonance in the gold nanoparticles. We present examples where we detect specific target sequences in oligonucleotides and in genomic DNA. Because conformational changes in special DNA sequences can also be induced by analytes such as potassium, we report a potassium ion detection scheme based on the same principle.     

限制性条件下药物对细菌抑制作用微量量热法研究

用微量量热计测定了福氏志贺氏菌(Shipella flexneri)中7株菌(6、2b、3b、sb、la、x、y)在合成药物抑制作用下生长的热谱图,按限制性条件下微生物生长的模型进行了数学处理,得出了比生长速率(μ),由此确定了各细菌比生长速率(μ)与药物浓度?之间的定量关系,求出了比生长速率(μ)为零时的用药浓度,并对该合成药对各细菌的抑菌效果进行了分析．     

微生物在矿物表面吸附的研究进展

微生物在矿物表面的吸附是微生物与矿物表面深度作用的前提, 也是生物药剂在选矿中的应用的基础研究。本文综述了影响微生物在矿物表面吸附的环境因素, 微生物细胞与矿物表面之间的相互作用, 微生物细胞表面基团、表面成分及其胞外聚合物对吸附过程的影响, 并提出了今后的研究方向。     

Allelopathic Bacteria and Their Impact on Higher Plants

The impact of allelopathic, nonpathogenic bacteria on plant growth in natural and agricultural ecosystems is discussed. In some natural ecosystems, evidence supports the view that in the vicinity of some allelopathically active perennials (e.g., Adenostoma fasciculatum, California), in addition to allelochemicals leached from the shrub's canopy, accumulation of phytotoxic bacteria or other allelopathic microorganisms amplify retardation of annuals. In agricultural ecosystems allelopathic bacteria may evolve in areas where a single crop is grown successively, and the resulting yield decline cannot be restored by application of minerals. Transfer of soils from areas where crop suppression had been recorded into an unaffected area induced crop retardation without readily apparent symptoms of plant disease. Susceptibility of higher plants to deleterious rhizobacteria is often manifested in sandy or so-called skeletal soils. Evaluation of phytotoxic activity under controlled conditions, as well as ways to apply allelopathic bacteria in the field, is approached. The allelopathic effect may occur directly through the release of allelochemicals by a bacterium that affects susceptible plant(s) or indirectly through the suppression of an essential symbiont. The process is affected by nutritional and other environmental conditions, some may control bacterial density and the rate of production of allelochemicals. Allelopathic nonpathogenic bacteria include a wide range of genera and secrete a diverse group of plant growth-mediating allelochemicals. Although a limited number of plant growth-promoting bacterial allelochemicals have been identified, a considerable number of highly diversified growth-inhibiting allelochemicals have been isolated and characterized. Some species may produce more than one allelochemical; for example, three different phyotoxins, geldanamycin, nigericin, and hydanthocidin, were isolated from Streptomyces hygroscopicus. Efforts to introduce naturally produced allelochemicals as plant growth-regulating agents in agriculture have yielded two commercial herbicides, phosphinothricin, a product of Streptomyces viridochromogenes, and bialaphos from S. hygroscopicus. Many species of allelopathic bacteria that affect growth of higher plants are not plant specific, but some do exhibit specificity; for example, dicotyledonous plants were more susceptible to Pseudomonas putida than were monocotyledons. Differential susceptibility of higher plants to allelopathic bacteria was noted also in much lower taxonomical categories, at the subspecies level, in different cultivars of wheat, or of lettuce. Therefore, when test plants are employed to evaluate bacterial allelopathy, final evaluation must include those species that are assumed to be suppressed in nature. The release of allelochemicals from plant residues in plots of ‘continuous crop cultivation’ or from allelopathic living plants may induce the development of specific allelopathic bacteria. Both the rate by which a bacterium gains from its allelopathic activity through utilizing plant excretions, and the reasons for the developing of allelopathic bacteria in such habitats, are important goals for further research.     

Temperature dependence of the transition enthalpy of core particle DNA and of long DNA

The denaturation of short (145 base pairs) and long (about 8000 base pairs) DNA moelucules has been studied by adiabitic differential microcalorimetry in solutions with different NaCl content. It is found that the enthalpy of denaturation of short DNA is more sensitive to changes in T_m than that of long DNA. A comparison with other data is also given.     

深海细菌及其适压机制

深海是以高压为主要特征的极端环境。在深海中适压生活的细菌在分类上多属于蛋白细菌(Pro-teobacteria)类群的γ分支。深海细菌对高压的适应可表现为嗜压或耐压,其适压的机制包括细胞膜脂成分中不饱和脂肪酸的增加,此外,细菌细胞的呼吸链系统也与耐压有关。     

Evaluation of the Adsorption of Mono- and Polytungstates onto Different Types of Clay Minerals and Pahokee Peat

Detailed knowledge about the fate and transport of tungsten in soils is critical to understanding and effectively addressing tungsten behavior in the environment. Recent studies have shown that tungsten anions may polymerize (depending upon concentration, pH, and aquatic geochemistry) in aquatic and soil systems. However, to date, of all soluble tungstate species only monotungstates have been scrutinized to a fair extent in adsorption studies. There is a lack of information evaluating adsorption mechanisms of mono- and polytungstates onto clay minerals. The objective of this work is to investigate the adsorption behavior of monotungstates (sodium tungstate, Na₂WO₄) and polytungstates (sodium metatungstate, 3Na₂WO₄·9WO₃) onto different types of clay minerals (montmorillonite, kaolinite, illite) and an organic adsorbent (Pahokee peat). Batch equilibrium experiments as a function of concentration (adsorption isotherms) and pH (adsorption envelopes) were performed to provide information about mono- and polytungstate adsorption onto clays and Pahokee peat. Adsorption equilibrium data for mono- and polytungstates onto different types of clay minerals and Pahokee peat were modeled with Freundlich and Langmuir isotherms. The adsorption affinity of clays and Pahokee peat for monotungstates follows the order: Pahokee peat>kaolinite>montmorillonite>illite; for polytungstates, the order is as follows: kaolinite>Pahokee peat>montmorillonite>illite. Results of this study suggest that the charges of the clay mineral surface, tungsten species, and solution pH are the main factors controlling tungsten adsorption. Moreover, polymeric tungsten species (i.e., metatungstate) appear to be more mobile in the environment than monomeric tungstate.     

Leptospirillum-Like Bacteria and Evaluation of Their Role in Pyrite Oxidation

Two strains of Leptospirillum-like bacteria isolated from dumps of Alaverdi and Akhtala sulfide ore deposits in Armenia were studied. The optimum and maximum temperatures for the growth of both strains were 37 and 40°C, respectively. The pH optimum was 2.0–2.3. Bacterial growth and ferrous iron oxidation were inhibited by yeast extract. The pyrite-leaching activity of the Leptospirillum-like bacteria under mesophilic conditions was close to that of Acidithiobacillus ferrooxidans and exceeded by 2.0–2.7 times the activity of these moderately thermophilic bacteria at 37°C. The leaching of pyrite by Leptospirillum-like bacteria increased in the presence of sulfur-oxidizing bacteria, particularly, in their association with a thermotolerant sulfur-oxidizing bacterium.