Structural purity of magnetite nanoparticles in magnetotactic bacteria

Magnetosome biomineralization and chain formation in magnetotactic bacteria are two processes that are highly controlled at the cellular level in order to form cellular magnetic dipoles. However, even if the magnetosome chains are well characterized, controversial results about the microstructure of magnetosomes were obtained and its possible influence in the formation of the magnetic dipole is to be specified. For the first time, the microstructure of intracellular magnetosomes was investigated using high-resolution synchrotron X-ray diffraction. Significant differences in the lattice parameter were found between intracellular magnetosomes from cultured magnetotactic bacteria and isolated ones. Through comparison with abiotic control materials of similar size, we show that this difference can be associated with different oxidation states and that the biogenic nanomagnetite is stoichiometric, i.e. structurally pure whereas isolated magnetosomes are slightly oxidized. The hierarchical structuring of the magnetosome chain thus starts with the formation of structurally pure magnetite nanoparticles that in turn might influence the magnetic property of the magnetosome chains.     

Micro-goethite in percolated water from Fushui Reservoir in Hubei Province,China

The sediments in the percolated water from Fushui Reservoir have been studied. The cause for formation of a special-shaped micro-goethite in the modern depositional environment (reservoir) as well as the action and the significance of microorganism in the biomineralization of iron are discussed in this paper. Tests show that the main cations in the percolated water include Ca²⁺, Mg²⁺, K⁺ and Na⁺, with minor Fe²⁺ and Fe³⁺, whereas the main anion is HCO₃⁻. The sediments from the percolated water are mainly oxidized products of iron. The mineral phase and the form of the particles from percolated water in Fushui Reservoir are studied by such means as powder X-ray diffraction (XRD), differential thermal analysis (DTA), infrared spectroscopic analysis (IR), Mössbauer spectrum, transmission electron microscope (TEM) and scanning electron microscope (SEM). The main mineral phases include goethite, quartz, illite, montmorillonite and small amounts of calcite, only slightly crystallized. The Mössbauer spectral characteristics and the special form of goethite imply that goethite originated from ferric bacteria. The following results can be reached: the sediments in Fushui Reservoir are mainly composed of amorphous ferric hydroxide colloid and weakly crystalline goethite; the genesis of goethite is related with ferric bacteria.     

青岛汇泉湾海洋趋磁细菌多样性研究

在青岛汇泉湾沿岸沉积物中发现了大量海洋趋磁细菌,最大丰度可达105 个/cm3.透射电镜观察发现该菌菌体形态多样,有球形或卵球形、长短杆状、弧状和螺旋状,其中球形或卵球形趋磁细菌占绝对优势.电镜观察还发现该菌磁小体的排列方式多样化,大多数呈链状排列,有单链、双链及多链,还有的呈环状或者成簇排列.磁小体的形态也多种多样,有正方体、棱柱体、立方八面体、子弹头状、片状和齿状.用RFLP方法分析了70个克隆测序,得到10条不同序列.经16S rRNA系统发育分析,发现9个属于α-变形菌亚纲,1个属于γ-变形菌亚纲,共有8个不同的属,优势种属于未培养的海洋趋磁球菌.所有菌株与最接近的海洋趋磁球菌的相似性并不高(76.4%～89.4%),表明该海区的趋磁细菌为新发现的微生物资源.     

Crystal growth of bullet-shaped magnetite in magnetotactic bacteria of the Nitrospirae phylum

Magnetotactic bacteria (MTB) are known to produce single-domain magnetite or greigite crystals within intracellular membrane organelles and to navigate along the Earth''s magnetic field lines. MTB have been suggested as being one of the most ancient biomineralizing metabolisms on the Earth and they represent a fundamental model of intracellular biomineralization. Moreover, the determination of their specific crystallographic signature (e.g. structure and morphology) is essential for palaeoenvironmental and ancient-life studies. Yet, the mechanisms of MTB biomineralization remain poorly understood, although this process has been extensively studied in several cultured MTB strains in the Proteobacteria phylum. Here, we show a comprehensive transmission electron microscopy (TEM) study of magnetic and structural properties down to atomic scales on bullet-shaped magnetites produced by the uncultured strain MYR-1 belonging to the Nitrospirae phylum, a deeply branching phylogenetic MTB group. We observed a multiple-step crystal growth of MYR-1 magnetite: initial isotropic growth forming cubo-octahedral particles (less than approx. 40 nm), subsequent anisotropic growth and a systematic final elongation along [001] direction. During the crystal growth, one major {111} face is well developed and preserved at the larger basal end of the crystal. The basal {111} face appears to be terminated by a tetrahedral–octahedral-mixed iron surface, suggesting dimensional advantages for binding protein(s), which may template the crystallization of magnetite. This study offers new insights for understanding magnetite biomineralization within the Nitrospirae phylum.     

Production, modification and bio-applications of magnetic nanoparticles gestated by magnetotactic bacteria

Magnetotactic bacteria (MTB) were first discovered by Richard P. Blakemore in 1975, and this led to the discovery of a wide collection of microorganisms with similar features i.e., the ability to internalize Fe and convert it into magnetic nanoparticles, in the form of either magnetite (Fe₃O₄) or greigite (Fe₃S₄). Studies showed that these particles are highly crystalline, monodisperse, bioengineerable and have high magnetism that is comparable to those made by advanced synthetic methods, making them candidate materials for a broad range of bio-applications. In this review article, the history of the discovery of MTB and subsequent efforts to elucidate the mechanisms behind the magnetosome formation are briefly covered. The focus is on how to utilize the knowledge gained from fundamental studies to fabricate functional MTB nanoparticles (MTB-NPs) that are capable of tackling real biomedical problems.     

Biodegradation of fenoxaprop-p-ethyl by bacteria isolated from sludge

A mixed bacterial population was isolated using enrichment in a basal medium containing increasing amounts of fenoxaprop-p-ethyl as a sole carbon source from sludge that had been exposed to fenoxaprop-p-ethyl production wastewater for about 2 years. Eight kinds of isolates could utilize fenoxaprop-p-ethyl, but only one was identified belonging to genus Alcaligenes, named Alcaligenes sp. H. In pure culture, there was 45.8, 66.0 and 69.5% loss of fenoxaprop-p-ethyl (initial concentration: 100, 50, 25 ppm, respectively) as the sole carbon source with biodegradation by Alcaligenes sp. H and fenoxaprop-p-ethyl degradation kinetics obeyed the first-order kinetics, the same as the fenoxaprop-p-ethyl biodegradation kinetics in soil. At least five degradation products of fenoxaprop-p-ethyl biodegradation by Alcaligenes sp. H and two degradation products of fenoxaprop-p-ethyl biodegradation by Huv separated by HPTLC. It is possible that the fenoxaprop-p-ethyl biodegradation by Alcaligenes sp. H includes the same pathway as that by Huv comparing with the Rf.     

攀枝花铁矿降低爆破噪声的措施

通过对攀枝花铁矿狮子山爆区产生爆破噪声的特性分析,找到了爆破噪声超标是爆破单段药量过大、装药结构不合理、地表网路缺陷等原因,提出了采用孔内孔间延时爆破方式、控制炮孔内每段装药长度、覆盖爆破声源体、选择较好的高精度雷管等一系列降低爆破噪声的措施,在攀枝花铁矿狮子山1 225～1 210 m台阶爆区进行实验,取得了较好地降低爆破噪声的效果。解决了爆破噪声影响周边居民生活的问题,也为矿山生产创造了良好的条件。     

Synthesis of mesoporous silica materials (MCM-41) from iron ore tailings

Highly ordered mesoporous materials were successfully synthesized by using the iron ore tailings as the silica source and n-hexadecyltrimethyl ammonium bromide as the template. The samples were detail characterized by powder X-ray diffraction, scanning electron microscope, high-resolution transmission electron microscopy and N₂ physisorption. The as-synthesized materials had high surface area of 527 m² g⁻¹ and the mean pore diameter of 2.65 nm with a well-ordered two-dimensional hexagonal structure. It is feasible to prepare mesoporous MCM-41 materials using the iron ore tailings as precursor.     

Characterization of lead-resistant and ACC deaminase-producing endophytic bacteria and their potential in promoting lead accumulation of rape

Forty-nine lead (Pb)-resistant endophytic bacteria were isolated from metal-tolerant Commelina communis plants grown on lead and zinc mine tailing, of which, seven 1-aminocyclopropane-1-carboxylate (ACC) deaminase-producing endophytic bacteria were initially obtained and characterized with respect to heavy metal resistance and production of ACC deaminase, indole-3-acetic acid (IAA) as well as siderophores. Two isolates (Q2BJ2 and Q2BG1) showing higher ACC deaminase activity were evaluated for promoting plant growth and Pb uptake of rape grown in quartz sand containing 0 and 100 mg kg(-1) of Pb in pot experiments. The seven Pb-resistant and ACC deaminase-producing endophytic bacterial isolates were found to exhibit different multiple heavy metal resistance characteristics and to show different levels of ACC deaminase activity (ranging from 12.8 μM α-KB mg(-1) h(-1) to 121 μM α-KB mg(-1) h(-1)). Among the seven isolates, six isolates produced indole acetic acid, whilst five isolates produced siderophores. In experiments involving rape plants grown in quartz sand containing 100 mg kg(-1) of Pb, inoculation with the isolates resulted in the increased dry weights of above-ground tissues (ranging from 39% to 71%) and roots (ranging from 35% to 123%) compared to the uninoculated control. Increases in above-ground tissue Pb contents of rape cultivated in 100 mg kg(-1) of Pb-contaminated substrates varied from 58% to 62% in inoculated-rape plants compared to the uninoculated control.     

Characterization study and recovery of copper from low grade copper ore through hydrometallurgical route

Characterization studies were conducted on low grade copper ore with the aid of standard approaches. The Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS) study specifies the semi-quantitative data of qualitatively analyzed chemical elements present in the ore sample. Optical Microscopy (OM) and X-Ray Diffraction (XRD) endorse the presence of chalcopyrite (CuFeS₂) and pyrites along with other different mineral phases in the ore sample. Thermo Gravimetric Analysis (TGA) and Mossbauer spectroscopy studies confirm the formation of CuO and Fe₂O₃ after roasting at 700 °C. The better copper recovery from low grade copper ore was achieved through optimized leaching parameters. It was found that the particle size of ?63+53 µm can be leached up to 94.96 % of copper using a lixiviant reagent mixture (30 vol. % hydrogen peroxide and 0.5 M sulfuric acid) under magnetic stirring for 30 min at a constant speed of 300 rpm, by keeping the liquid/solid (L/S) ratio at 20/2 ml/g. Moreover, the solvent extraction process works well with the pregnant leach solution, whereby, 98.9 % of copper extraction is possible, and the loading time is less than a minute. Meanwhile, 93.91 % of overall copper extraction efficiency was achieved through optimized leaching parameters and solvent extraction method.     

Dielectric behaviour of MgFe2O4 prepared from chemically beneficiated iron ore rejects

Chemically beneficiated high silica/alumina iron ore rejects (27–76% Fe₂O₃) were used to synthesize iron oxides of purity 96–98% with SiO₂/Al₂O₃ ratio reduced to 0.03. The major impurities on chemical beneficiations were Al, Si, and Mn in the range 2–3%. A 99.73% purity Fe₂O₃ was also prepared by solvent extraction method using methyl isobutyl ketone (MIBK) from the acid extracts of the ore rejects. The magnesium ferrite, MgFe₂O₄, prepared from these synthetic iron oxides showed high resistivity of ∼ 10⁸ ohm cm. All ferrites showed saturation magnetization, 4πM_s, in the narrow range of 900–1200 Gauss and the Curie temperature,T, _cof all these fell within a small limit of 670 ± 30 K. All ferrites had low dielectric constants (ε′), 12–15, and low dielectric loss, tan δ, which decreased with the increase in frequency indicating a normal dielectric dispersion found in ferrites. The presence of insignificant amount of polarizable Fe²⁺ ions can be attributed to their high resistances and low dielectric constants. Impurities inherent in the samples had no marked influence on the electrical properties of the ferrites prepared from the iron ore rejects, suggesting the possibility of formation of ferrite of constant composition, MgFe₂O₄, of low magnetic and dielectric losses at lower temperatures of 1000°C by ceramic technique.     

Soft-magnetic composites from insulated iron powder and their potential technological applications

We have studied soft-magnetic composite materials fabricated from iron powder encapsulated in magnetic oxides. The results demonstrate that the use of such materials in power supplies, electric motors, and other devices ensures their stable operation under various conditions.     

Isolation and characterization of the heavy metal resistant bacteria CCNWRS33-2 isolated from root nodule of Lespedeza cuneata in gold mine tailings in China

A total of 108 strains of bacteria were isolated from root nodules of wild legumes growing in gold mine tailings in northwest of China and were tested for heavy metal resistance. The results showed that the bacterial strain CCNWRS33-2 isolated from Lespedeza cuneata was highly resistant to copper, cadmium, lead and zinc. The strain had a relatively high mean specific growth rate under each heavy metal stress test and exhibited a high degree of bioaccumulation ability. The partial sequence of the copper resistance gene copA was amplified from the strain and a sequence comparison with our Cu-resistant PCR fragment showed a high homology with Cu-resistant genes from other bacteria. Phylogenetic analysis based on the 16S rRNA gene sequence showed that CCNWRS33-2 belongs to the Rhizobium-Agrobacterium branch and it had 98.9% similarity to Agrobactrium tumefaciens LMG196.     

Mathematical modeling and distribution characteristics evaluation of fuel particles in iron ore sintering process

The distribution characteristics of fuel particles is a key factor affecting the thermal state of sintering. To find out the fuel distribution under different granulation conditions, a mathematical method based on the particle population balance and Lister’s model was established in this study. In combination with experiments including granulation and the fixed carbon and sulfur content of detection, the relative error of this model is within ±1.5. The proportion and particle size composition of fuel are selected to evaluate quantitatively the distribution characteristics. The result shows that the fuel distribution in granules mostly accumulates in the middle size granules. The increase of proportion and fine particles content of the fuel leads to the decline of the fuel content in +5 mm granules. With a higher ratio and higher content of fine particles in the fuel, the fuel distribution in the upper and middle of the sintering beds rises while that of the bottom layer is down, which is conducive to changing the nonuniform distribution of thermal. The fuel particle size composition has greater impact on fuel distribution than its proportion. To better investigation, further parameter simulation and optimization of granulation is necessary.     

Characterization of explosively bonded iron and copper plates

Explosive bonding between iron and copper plates was achieved under various conditions. A variety of experimental techniques were applied in order to investigate the bonding interface, including metallography, scanning electron microscopy, X-ray micro-analysis and X-ray diffraction. It was found that the bonding characteristics depend on the ratio of the explosive weight to the flyer plate weight (R ratio) and on the distance (X) from the detonation point. The microstructure of the molten pockets obtained depends strongly on their composition and on the cooling rate. Increasing the copper content in the molten pocket and the cooling rate resulted in a finer structure. Microstructural similarities between electron-beam molten surfaces and molten pockets in explosively bonded plates indicate, that cooling rates as high as 10⁵ K sec^–1 are obtained in both cases.     

湖北少数民族服饰文化的传承和发展

探讨了湖北地区少数民族服饰特点和现状,认为传统民族服饰的传承必须依托当地的民族生态环境,在发展旅游经济的同时强化民族自豪感;认为对传统民族服饰的发展与创新必须把握其民族心理和精神定位,必须符合当代人的生活方式。     

Characterization of phyto-nanoparticles from Ficus krishnae for their antibacterial and anticancer activities

Background: Ovarian cancer is deadliest of fifth leading cause of death in women worldwide. This is due to advanced-stage disease rate associated with the development of chemoresistance. Hence, the current study emphasizes the process of synthesis of silver nanoparticles (AgNPs) from green chemistry method. Ficus krishnae is a perennial plant, native to India, used in folklore medicine to treat various diseases.

Objective: For the development of reliable, ecofriendly, less expensive process for the synthesis of AgNPs against bacterial and ovarian cancer.

Methodology: The synthesis of silver nanoparticles from stem bark of Ficus krishnae was carried out. The synthesized nanoparticles are subjected by UV-Vis spectrophotometer, scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and FTIR analysis. The antibacterial efficacy also determined by disc diffusion method, MIC, CFU and growth curve. In vitro cytotoxicity effect of aqueous extract and AgFK nanoparticle in ovarian cancer cell line by MTT assay was performed.

Results: The formation of AgNPs was confirmed by UV-VIS spectroscopic absorbance shown that peak at 435?nm. XRD photograph has indicated the face-centered cubic structure of the synthesized AgNPs. SEM study demonstrated that the size from 160 to 260?nm with interparticle distance, whereas shape is spherical. The particle size were ranging from 15 to 28?nm determined by XRD pattern. The antibacterial and cytotoxicity activity of this nanoparticle has showed a potential activity when compared with standards.

Conclusion: The present study confirms that the biosynthesized AgNPs from Ficus krishnae stem bark extract have a great affiance as antibacterial and anticancer agent.     

Characterization and in vivo evaluation of a bio-corrodible nitrided iron stent

A bio-corrodible nitrided iron stent was developed using a vacuum plasma nitriding technique. In the nitrided iron stents, the tensile strength, radial strength, stiffness and in vitro electrochemical corrosion rate were significantly increased compared with those of the control pure iron stent. To evaluate its performance in vivo, the deployment of the nitrided iron stents in juvenile pig iliac arteries was performed. At 3 or 6 months postoperatively, the stented vessels remained patent well; however, slight luminal loss resulting from intimal hyperplasia and relative stenosis of the stented vessel segment with piglets growth were observed by 12 months; no thrombosis or local tissue necrosis was found. At 1 month postoperatively, a nearly intact layer of endothelial cells formed on the stented vessel wall. Additionally, a decreased inflammation scoring, considerably corroded struts and corrosion products accumulation were seen. These findings indicate the potential of this nitrided iron stent as an attractive biodegradable stent.     

Bio-synthesis of gold and silver nanoparticles from Candida guilliermondii and their antimicrobial effect against pathogenic bacteria

In the present study we investigated the extra cellular synthesis of gold and silver nanoparticles by using the yeast Candida guilliermondii. The formation of noble metal nanoparticles was monitored by the UV-Visible spectroscopy. As prepared gold and silver nanoparticles showed distinct surface plasmon peaks at 530 nm and 425 nm respectively. Phase and morphology of the as synthesized materials were investigated by X-ray diffraction and electron microscopy techniques respectively. XRD patterns confirmed the formation of gold and silver nanoparticles with face centered cubic structures. Bio-TEM images showed the formation of near spherical, well dispersed gold and silver nanoparticles in the size range of 50-70 nm and 10-20 nm respectively. The biosynthesized nanoparticles were tested for their antimicrobial activity against five pathogenic bacterial strains. The highest efficiency for both gold and silver nanoparticles was observed against Staphylococcus aureus. A comparative study was also done to find the effect of chemically synthesized noble metal nanoparticles against the above test strains. Chemically synthesized particles had no antimicrobial activity against any of the pathogenic strains. The results obtained suggest that biosynthesized gold and silver nanoparticles can be used as effective antimicrobial agents against some of the potential harmful pathogenic microorganisms.