新型海洋趋磁细菌YSC-1的磁性能分析

对从黄海冷水团附近海域的底泥中分离到的一株新型海洋趋磁细菌YSC-1的磁特性进行了分析。对YSC-1菌株进行的磁铁吸附实验显示YSC-1菌株有一定的磁性、核磁共振(MRI)测定表明菌体中包含磁性材料,磁性能测量结果证明YSC-1的菌体沉淀有磁性,但磁性较弱,磁滞回线测量显示YSC-1菌株中含有铁磁材料,饱和磁矩约为40memu/g。每个细菌的磁矩为:3.06×10-14emu。     

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.     

脉冲磁场对趋磁螺细菌AMB-1磁小体形成及相关基因表达的影响

本文利用Cmag测量、透射电镜观察等技术研究了脉冲磁场对不同初始状态的趋磁螺细菌AMB-1(Magnetospirillum magneticum AMB-1)磁小体形成的影响,并对其相关蛋白MamA、Mms13、Mms6和MagA编码基因的表达情况做了荧光实时定量反转录聚合酶链式反应(qRT-PCR).结果表明:同自然地磁场相比,50Hz、1mT脉冲磁场可促进AMB-1磁小体形成;当初始菌种为含有磁小体的AMB-1时,脉冲磁场促进指数期菌体magA基因的表达;而当初始菌种为不含磁小体的AMB-1时,则促进指数期菌体magA和mamA基因的表达.脉冲磁场虽然导致指数期细胞磁颗粒不均匀,但使磁小体链加长,含磁小体菌的平均磁颗粒数也较地磁场明显增加.实验结果为应用磁场干预磁小体形成,提高磁小体产率的研究提供了实验和理论依据,也有助于进一步了解磁场的生物学效应.     

生物无机铁磁纳米粒子酶活性能研究

采用酶标分析仪,在H2O2存在的情况下,研究了原核生物趋磁细菌天然合成的磁性纳米颗粒——磁小体具有内在的类似于过氧化物酶的酶活性能。结果显示,随着缓冲液的pH值、反应温度和H2O2浓度的增加,磁小体的所有酶活性能皆呈＂抛物线＂型变化,满足酶学中关于酶催化反应性能的解释。由此得出磁小体催化反应的最适pH是4.0值,最佳温度是30℃,最佳H2O2浓度是0.28mol/L。随后,进一步考察了磁小体的酶活稳定性。结果显示在pH值从0.2～12.9变化的不同缓冲液浸泡2h之后的磁小体的类酶活性保持在60%以上;从4～97℃不同温度孵育磁小体2h,磁小体的类酶活性没有明显下降。所有结果表明处理之后的磁小体仍能保持优异的酶催化稳定性。     

基于电/磁转换的海洋电场检测方法

传统的直接电测量方法受1/f噪声限制,在低频处信号与噪声发生混叠,难以实现高水平低噪声测量。该文提出一种基于电/磁转换的海洋电场低噪声检测方法,将电信号转化为磁信号,通过微机械的方法将磁信号调制到高频,有效避开低频1/f噪声影响。设计一种实现电/磁转换功能的微机械结构,利用TMR电阻构成惠斯通电桥测量磁信号,实现海洋电场的高水平低噪声检测。仿真与实验结果在1 Hz处噪声分别达到1.16 nV/(Hz)~(1/2)和1.41 nV/(Hz)~(1/2),优于传统电测量方案的噪声水平,验证该方法的有效性。     

La空位掺杂对La-Ca-Sr-MnO_3磁热性质的影响

用溶胶-凝胶法制备了不同空位掺杂的系列样品La_(0.7-x)Ca_(0.28)Sr_(0.02)MnO_3,研究了La~(3+)空位浓度对样品居里温度和磁热效应的影响。结果表明,在La位掺入少量空位(x0.06),可以实现将样品的居里温度有效调整至室温,同时也促进了样品磁熵变的提高。当La空位掺杂x=0.06时,与未空位掺杂样品相比,居里温度由227 K提高到264 K,近室温,其磁熵变值为3.01 J·kg-1·K-1(外加磁场1 T)。该系列样品在室温附近,较低磁场下,有较强的磁制冷能力。     

旋甩快淬带ErCoSi的各向异性磁热效应

磁制冷技术的关键在于磁热效应材料的发展。具有各向异性磁热效应的新型磁制冷材料可以用于旋转磁制冷技术而被广泛研究。研究了ErCoSi旋甩快淬带化合物的磁性、磁热效应及磁各向异性。在T_c=5.5 K处发生了铁磁(FM)到顺磁(PM)的二级相变。通过分析5 m/s-ErCoSi快淬带在磁场//和⊥横截面的两个方向的等温磁化曲线、磁熵变和磁制冷能力可知,在μ₀H=0～5 T的磁场变化时,磁场//和⊥快淬带横截面的最大磁熵变值-ΔS_M分别为17.5 J·kg^-1 k^-1和12 J·kg^-1 k^-1;制冷能力分别可达230 J·kg^-1和120 J·kg^-1.表明5 m/s-ErCoSi快淬带具有大的磁热效应和明显的磁各向异性,有望实现旋转样品磁制冷技术.     

厦门海域产蛋白酶浮游细菌的多样性研究

从厦门海域分离筛选到33株产蛋白酶浮游细菌,并通过对其16S核糖体RNA(16S rRNA)基因进行聚合酶链式反应(PCR)扩增和限制性片段长度多态性(RFLP)分析,初步研究了该海域产蛋白酶浮游细菌的多样性.研究发现,这33株菌可分为12种操作分类单元(OTU),其中OTU-Ⅰ和OTU-Ⅱ分别包含8株和12株菌株,分别占总菌数的24.2%和36.4%,为优势分离类群.分别从12种OTU中随机选取1株细菌作为代表进行16S rRNA基因测序.序列分析结果显示,属于OTU-Ⅶ的细菌为假交替单胞菌属(Pseudoalteromonas sp.),而包括OTU-Ⅰ和OTU-Ⅱ在内的9种OTU 都属于弧菌属(Vibrio sp.),表明弧菌在厦门海域产蛋白酶浮游细菌中占优势.初步的生理检测显示,这些细菌的适宜生长温度为16℃左右,适宜生长盐度范围为3%～5% NaCl.     

室温磁工质与磁制冷机的研究和开发

室温磁制冷作为一种高能效、环境友好和运行可靠的制冷技术,具有广阔的应用前景。室温磁制冷技术利用磁工质的磁热效应以及AMR循环实现制冷。在过去数十年的探索中,室温磁制冷的研究主要集中于磁工质的研发和磁制冷机的设计。本文综述了目前已开发的几种典型的室温磁工质以及研制的磁制冷样机。目前研究较丰富的室温磁工质主要包括稀土金属Gd及其合金、NaZn₁₃型La(Fe, Si)₁₃系合金以及Fe₂P型MnFePAs系合金,本文对它们的磁热性能进行对比并分析存在的实际应用问题。基于运行方式的不同,目前研制的磁制冷样机主要分为往复式和旋转式,介绍了不同研究机构研发的磁制冷样机的实验参数与制冷性能。回顾了室温磁制冷技术在不同领域已取得的实际应用,并对该技术未来的发展趋势进行展望。     

Gd2Co2Al合金的磁相变及磁热效应

电弧炉熔炼的Gd2Co2Al合金在铸态条件下即为W2Co2B型单相正交结构。变温磁化曲线表明,当外加磁场为0.01和0.1T时,可以在40、77和215K附近观察到磁相变;而外加磁场增加到1T以上时,40和215K温度处的磁相变消失。在排除第二相相变的前提下,推测215和77K处的相变对应Gd2Co2Al合金中Co和Gd次晶格的磁有序相变,而40K处的相变可能是由于自旋重取向产生。在0～5T磁场变化下,Gd2Co2Al合金在77K附近的最大磁熵变(-ΔSMmax)为10.7J/kgK,相对制冷量的值为5.4×102J/kg,表明该合金适合作为工作在液氮温区附近的磁致冷工质。     

Bacteria contributing to behaviour of radiocarbon in sodium acetate

An acetate-utilising bacterium was isolated and identified from deionised water that was used for flooding of paddy soils in this study's batch culture experiments. Bacteria in the deionised water samples formed colonies on agar plates containing [1,2-(14)C] sodium acetate, and the autoradiograms showed that all the colonies were positive for (14)C utilisation. Then one of the acetate-utilising bacteria was isolated. The isolate was characterised by phylogenetic analysis, cell morphology, Gram staining and growth at 30 °C. Phylogenetic analysis based on 16S rRNA sequencing showed that the isolate belonged to the genus Burkholderia. The bacterium was gram-negative rods and grew at 30 °C under aerobic conditions. Based on these characteristics, the isolate was identified as Burkholderia gladioli. Because B. gladioli is often found in soil, water and the rhizosphere, attention must be paid to the relationships between bacteria and the behaviour of (14)C to for the safety assessment of geological disposal of transuranic waste.     

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.     

Characterization of magnetotactic bacteria and their magnetosomes isolated from Tieshan iron ore in Hubei Province of China

Several magnetotactic bacteria (MTB) have been isolated from iron cap belt, surface soil of intermediate belt and “primary iron ore belt” of Tieshan iron ore in Hubei Province, China. These magnetotactic bacteria were cultivated in enrichment medium at room temperature (25–30 °C), with oxygen concentration of 5–10% under the field of a permanent magnet. The magnetotactic bacteria were cocci or rods. They contained two or more magnetosomes under transmission electron microscope (TEM H-7000 FA), and the magnetosomes were in the shapes of rounded, triangular, rectangular and irregular. Energy spectrum analysis with Jeol 2000 transmission electron microscope (JEM2000FXII) equipped with energy dispersive system (EDS) controlled by Oxford Instruments Analytical system (INCA) showed that iron oxides were the main component of the magnetic particles.     

Factors affecting the biodegradation of PCP by Pseudomonas mendocina NSYSU

A pentachlorophenol (PCP) degrading bacterium was isolated from PCP-contaminated soils and identified as Pseudomonas mendocina NSYSU (P. mendocina NSYSU). The main objectives of this study were to (1) clarify the factors affecting the ability and efficiency of PCP biodegradation by P. mendocina NSYSU, and (2) optimize the use of this bacterium in bioremediation of PCP. Microcosm experiments were conducted to fulfill the objectives. In batch cultures, P. mendocina NSYSU used PCP as its sole source of carbon and energy and was capable of completely degrading this compound. This was confirmed by the stoichiometric release of chloride ion. Moreover, P. mendocina NSYSU was able to mineralize a high concentration of PCP (150 mg/L). Results from the oxygen concentration experiment reveal that the growth of P. mendocina NSYSU was inhibited under low oxygen and anaerobic conditions. Results indicate that the optimal growth conditions for P. mendocina NSYSU include the following: slightly acidic (6相似文献   

氯代芳香族污染物生物降解菌株的分离及其降解质粒的初步研究

从工业废水污染的水体和污泥中,分离并筛选到６株对氯苯和苯酚类有机污染物高浓度耐受力的细菌菌株。６株降解细菌能在氯代苯和氯代酚作为唯一碳源的培养介质中生长,具有不同程度降解这类有机污染物的代谢能力,除２号和５号菌外,所筛选的其它４株降解细菌均含有一个或多个质粒。采用２,４－Ｄ单加氧酶基因ｔｆｄＡ的保守引物和ＰＣＲ扩增技术,证明在２号和６力的染色体和３号菌的大质粒上含有ｔｆｄＡ基因的同源序列。     

Biological detoxification of Cr(VI) using wood-husk immobilized Acinetobacter haemolyticus

Acinetobacter haemolyticus, a Gram-negative aerobic locally isolated bacterium, immobilized on wood-husk showed the ability to detoxify Cr(VI) to Cr(III). Wood-husk, a natural cellulose-based support material, packed in an upward-flow column was used as support material for bacterial attachment. Around 97% of the Cr(VI) in wastewater containing 15 mg L(-1) of Cr(VI) was reduced at a flow rate of 8.0 mL min(-1). The wastewater containing Cr(VI) was added with liquid pineapple wastewater as nutrient source for the bacteria. Electron microscopic examinations of the wood-husk after 42 days of column operation showed gradual colonization of the wood-husk by bacterial biofilm. The use of 0.1% (v/v) formaldehyde as a disinfecting agent inhibited growth of bacteria present in the final wastewater discharge. This finding is important in view of the ethical code regarding possible introduction of exogenous bacterial species into the environment.     

青岛和大连海区海带(Laminaria japonica)外生细菌的16S rRNA基因序列分析

从采集自青岛和大连的大型褐藻海带(Laminaria japonica)表面分离到22株革兰氏阴性海洋细菌。根据16SrRNA基因序列分析结果,将其分别鉴定为假交替单胞菌(Pseudoalteromonas,Cobetia)菌,嗜冷单胞菌(Psychromonas),交替单胞菌(Alteromonas),产碱杆菌(Alcaligens)和海杆菌(Marinobacter)。其中假交替单胞菌在两地样品中占据绝对优势,但每个产地的假交替单胞菌不能单独聚类在一起,不同海区的海带表面存在遗传关系非常接近的菌株。假交替单胞菌之外的其他菌株于两地样品之间存在种或属水平上的差异。本文结果提示外生细菌的种类既与环境相关,又受宿主的状况影响。对8株受试菌株的拮抗实验结果显示了外生细菌在寻找新型抗生素方面的潜力。     

Performance and dye-degrading bacteria isolation of a hybrid membrane process

Textile dyeing wastewater contains harmful compounds, which are toxic to both marine organisms and human beings if it discharged into an aquatic environmental without suitable treatment. In this study, the wastewater containing the azo dye, Reactive Black 5 (RB5), was partially treated in an anaerobic sequencing batch reactor which was further treated either in an aerobic membrane bioreactors (AOMBR) or in combined aerobic membrane bioreactor/reverse osmosis (AOMBR/RO) process. The results showed that in the anaerobic sequencing batch reactor the RB5 dye was degraded to form aromatic amine intermediate metabolites, which were further mineralized in the AOMBR. It was also observed that although all effluents from the AOMBR and AOMBR/RO processes met the Taiwan EPA's effluent criteria, irrespective of which membranes were used in the aerobic tank, the effluent from the AOMBR/RO process met the criteria for reuse for toilet flushing, landscaping, irrigation, and cooling water purposes, where as the AOMBR effluent only met the criteria for cooling water due to incomplete color removal. Five anaerobic high dye-degrading bacteria were isolated, which were identified to be the same species of Lactococcus lactis by 16S rRNA sequencing. The L. lactis showed complete degradation of RB5 and further studies showed that it can also able to degrade Reactive Red 120 and Reactive Yellow 84 efficiently within 6 h.     

Long-Term Stability,Biocompatibility, and Magnetization of Suspensions of Isolated Bacterial Magnetosomes

Magnetosomes are magnetic nanoparticles biosynthesized by magnetotactic bacteria. Due to a genetically strictly controlled biomineralization process, the ensuing magnetosomes have been envisioned as agents for biomedical and clinical applications. In the present work, different stability parameters of magnetosomes isolated from Magnetospirillum gryphiswaldense upon storage in suspension (HEPES buffer, 4 °C, nitrogen atmosphere) for one year in the absence of antibiotics are examined. The magnetic potency, measured by the saturation magnetization of the particle suspension, drops to one-third of its starting value within this year—about ten times slower than at ambient air and room temperature. The particle size distribution, the integrity of the surrounding magnetosome membrane, the colloidal stability, and the biocompatibility turn out to be not severely affected by long-term storage.     

A Versatile Toolkit for Controllable and Highly Selective Multifunctionalization of Bacterial Magnetic Nanoparticles

Their unique material characteristics, i.e. high crystallinity, strong magnetization, uniform shape and size, and the ability to engineer the enveloping membrane in vivo make bacterial magnetosomes highly interesting for many biomedical and biotechnological applications. In this study, a versatile toolkit is developed for the multifunctionalization of magnetic nanoparticles in the magnetotactic bacterium Magnetospirillum gryphiswaldense, and the use of several abundant magnetosome membrane proteins as anchors for functional moieties is explored. High‐level magnetosome display of cargo proteins enables the generation of engineered nanoparticles with several genetically encoded functionalities, including a core–shell structure, magnetization, two different catalytic activities, fluorescence and the presence of a versatile connector that allows the incorporation into a hydrogel‐based matrix by specific coupling reactions. The resulting reusable magnetic composite demonstrates the high potential of synthetic biology for the production of multifunctional nanomaterials, turning the magnetosome surface into a platform for specific versatile display of functional moieties.