Characterisation of Erwinia carotovora subspecies and detection of Erwinia carotovora subsp. atroseptica in potato plants, soil and water extracts with PCR-based methods

A PCR-RFLP test based on a pectate-lyase encoding gene permits the detection of several Erwinia carotovora subspecies, but requires complete DNA extraction. This paper reports on the suitability of a simplified PCR-RFLP protocol to characterise E. carotovora strains and on the performance of PCR, using the same primers, to detect the atroseptica subspecies in substrates of epidemiological significance. A collection of 140 strains from various hosts and geographical origins was characterised for biochemical traits and PCR-RFLPs. PCR performed on boiled bacterial suspensions yielded an amplification product of 434 bp in 109 of the 140 strains. None of the E. carotovora subsp. betavasculorum strains was amplified, even after complete DNA extraction. RFLPs of the PCR product yielded 24 groups, 3 of which were new. Twenty one groups were specific to one subspecies. Several strains biochemically similar to E. carotovora subsp. atroseptica, but growing at 37 °C, showed PCR-RFLP profiles characteristic of E. carotovora subsp. carotovora. Phenetic and cladistic analyses gave three main domains, not strictly related to hosts or geographical origins. The atroseptica (RFLP groups 1 and 2) and wasabiae (group 21) subspecies constituted one of the domains, despite clustering distantly from one another. Host specialisation and molecular homogeneity suggest a clonal structure within these subspecies. Conversely, E. carotovora subsp. odorifera, despite its limited host range and geographical distribution, and E. carotovora subsp. carotovora showed great molecular diversity, spreading respectively across five and 19 RFLP groups. These two subspecies shared RFLP groups 4, 5 and 6. The tree nodes in the phenograms showed a low robustness when bootstrapping the data matrix. PCR coupled with a 48h enrichment step in a polypectate-rich medium improved detection thresholds of E. carotovora subsp. atroseptica (1.5.10²- 1.5.10³ bacteria/ml in leaves, stems, and tuber peel extracts to 4.10⁷ bacteria/ml in wash water) relative to either immunomagnetic separation coupled with PCR or DAS-ELISA (2.10⁵ in plant samples to 2.10⁷ bacteria/ml in wash water).     

Immunomagnetic isolation of canine circulating endothelial and endothelial progenitor cells

Background: Increased concentrations of circulating endothelial cells (CECs) are thought to be a biomarker of vascular injury in human patients with cardiovascular disease, neoplasia, vasculitis, sickle cell anemia, shock, and sepsis. Immunomagnetic isolation is a technique currently used to enumerate human CECs and can detect low numbers of cells. Objectives: The purpose of this study was to determine whether a standard protocol for immunomagnetic isolation could be used to obtain and enumerate CECs and a subpopulation of endothelial progenitor cells (EPCs) from canine whole blood. Methods: Cultured canine aortic endothelial cells were stained immunohistochemically with von Willebrand factor to verify morphology and number. Using magnetic beads conjugated with anti‐CD146, CECs/EPCs were isolated in culture and in canine whole blood. CD146‐positive cells were stained with fluorescein‐conjugated Ulex europaeus agglutinin 1 (UEA‐1) to confirm endothelial origin and cells were counted manually using a fluorescent microscope. The method was then applied to EDTA‐anticoagulated whole blood samples from 10 healthy client‐owned dogs. Results: The anti‐CD146–coated magnetic beads (>5/cell) bound the cultured canine aortic endothelial cells. Only rare UEA‐1–positive cells were obtained from whole blood, while >85–90% of cultured canine aortic endothelial cells were UEA‐1 positive. The percentage recovery of cultured canine aortic endothelial cells was >86%. CECs in canine whole blood had >8 beads attached to the surface and were 10–40 μm in size. Using immunomagnetic isolation, 43.4 ± 15.6 CECs/mL (range 24–70/mL) were isolated from canine whole blood samples. Conclusions: Immunomagnetic isolation is an acceptable method for enumerating canine CECs/EPCs in whole blood. Further studies are warranted to evaluate the clinical significance of CEC/EPC concentration in different canine diseases.     

免疫磁性捕获ELISA技术在松材线虫检测中的应用

本研究采用种子聚合法合成聚苯乙烯磁性微球,并以兔抗松材线虫IgG致敏,制备出能特异性地捕获松材线虫蛋白抗原的免疫磁性微球。以生物素标记抗体为示踪抗体,并结合酶标亲和素检测系统,用于疫木样品的分析。利用该方法对采自不同地区的3种松树,其中松材线虫病木17株、拟松材线虫病木5株和健木3株进行检测。实验结果表明,虽然拟松材线虫病木也呈现了一定的交叉反应,但疫木中松材线虫总检出率为94.1%,灵敏度达到0.1μg.mL-1线虫蛋白抗原。研究表明免疫磁性捕获ELISA技术可直接捕获木屑中的微量线虫抗原,具有简便、快速、准确等优点,是一种实用的松材线虫的快速检疫方法。     

磁珠和蛋白质标签特异性免疫沉淀体系的建立

为建立植物中特异性免疫沉淀微量蛋白体系,以GUS为报告基因,利用Flag、Myc两种蛋白标签对GUS氨基端进行标记,以农杆菌为介导,在烟草叶片中瞬时高效表达GUS基因。利用Western blot检测叶片中标记的GUS蛋白含量,便于后续GUS蛋白的特异性纯化。以anti-Flag M2磁珠和anti-c-Myc琼脂糖为固相载体,特异性识别和结合标记的GUS蛋白,利用磁分离技术和特异性免疫沉淀对目的蛋白进行两次富集,通过Western blot检测对比各个步骤所得目的蛋白的含量判断富集纯化效果。结果表明,以磁珠和琼脂糖为载体的蛋白,经两次特异性免疫沉淀后得到明显富集和纯化,且每一次的富集效果都较好,初步建立了蛋白标签和磁珠法二次特异性免疫沉淀体系,为体外深入研究活性蛋白复合体奠定了一定的技术基础。     

含铁蛋白cyb5融合基因莱茵衣藻核转化表达载体的构建及转化

旨在构建并转化细胞色素cytb5基因的衣藻核转化表达载体,为其在衣藻叶绿体中对铁的利用情况研究奠定基础。将克隆的PsaD信号肽、细胞色素b5和增强型绿色荧光蛋白基因的基因融合,插入到pDBle载体中;采用玻璃珠法,将重组子导入莱茵衣藻(CW15)中;经博来霉素筛选获得转基因植株并鉴定。本项研究通过分子克隆技术获得了衣藻自身来源的PsaD信号肽、裂殖酵母来源的细胞色素b5和常用增强型绿色荧光蛋白基因片段;重组质粒pDBle-b5、pDBle-bG和pDBle-TbG测序完全正确;经博来霉素抗性筛选,获得转化衣藻单克隆;通过PCR检测转化衣藻基因组DNA,扩增片段与预期相符。实验结果表明,成功构建了pDBle-b5、pDBle-bG和pDBle-TbG衣藻核转化表达载体,重组质粒已整合到莱茵衣藻基因组中。     

三角帆蚌微卫星位点筛选及多态性分析

采用磁珠富集法,以生物素标记的(CA)10寡核苷酸为探针,构建了三角帆蚌(Hyriopsis cumingii)基因组微卫星富集文库。根据微卫星位点的侧翼序列设计引物,随机挑选扩增出与预期大小相符的32对引物,引物荧光标记后对24个三角帆蚌个体分别进行PCR扩增,共筛选出20对多态性较好的引物。结果表明,20个微卫星位点的等位基因数为5～20,有效等位基因数2.321 3～13.260 3。观察杂合度和期望杂合度分别为0.318 2～1.000 0和0.582 5～0.946 1;PIC值0.547 2～0.919 9;其中14个位点符合Hardy-Weinberg平衡(P>0.05)。本研究筛选的20个微卫星标记可作为三角帆蚌遗传多样性、种群遗传结构等研究的理想分子标记。     

一种快速检测阪崎肠杆菌的新方法——免疫磁性分离荧光标记

阪崎肠杆菌是肠杆菌科的一种,是人和动物肠道内寄生的一种革兰氏阴性无芽胞杆菌。我国于2005年8月批准了阪崎肠杆菌检测的行业标准,此标准改进了美国FDA的推荐方法。本文论述了一种基于免疫磁珠磁性分离、免疫量子点荧光标记联合应用的检测方法,本方法可灵敏、快速、高特异性的检出乳制品中的阪崎肠杆菌。     

基于免疫磁珠净化间接竞争酶联免疫吸附试验检测氟喹诺酮类药物

本研究旨在建立一种基于免疫磁珠进行分离、富集和净化前处理，检测鸡肉、鸡肝和鱼肉中氟喹诺酮类药物残留的间接竞争酶免疫吸附试验（indirect competitive enzyme-linked immunosorbent assay，icELISA）的研究方法。通过对合成免疫磁珠及免疫磁珠净化过程中单克隆抗体添加量、偶联时间、缓冲液pH、抗原添加量、抗原捕获时间、温度及包被条件等进行优化，初步建立了基于免疫磁珠净化的icELISA检测方法。结果显示：1）在1 mg的磁珠中，沙拉沙星（sarafloxacin，SAR）单克隆抗体最佳偶联量为15 μg，偶联时间60 min，pH为4.4；2）最佳抗原添加量为1 ng·mL^-1，捕获时间40 min，缓冲液为0.01 mol·L^-1 PBS，IC₅₀为0.73 ng·mL^-1，线性范围为1.0~3.2 ng·mL^-1；3）氟喹诺酮类药物在鸡肉、鸡肝、鱼肉的检测限均不超过1.33、2.17、2.31 μg·kg^-1，回收率为76.83%~98.70%，批内变异系数批间变异系数均不超过15%，经验证，鸡肉样本检测结果与高效液相色谱法（HPLC）结果一致。结果表明，与传统仪器检测方法相比，该方法提高了检测氟喹诺酮类药物的简便性、选择性以及检测效率，为氟喹诺酮类药物的残留检测提供了新思路。