Genotypic characteristics of the causal agent of chinaberry gall

Chinaberry (Melia azedarach) is a deciduous tree of moderate size, grown throughout warm countries. The plantation of M. azedarach tree improves the environmental condition of the country. During the years 1390–1391, bacterial gall symptoms were observed on chinaberry. The isolation of the causal agent bacteria was done on nutrient agar medium. Approximately 4 weeks after inoculation, galls developed on the chinaberries inoculated with different isolates. The specific primer was designed based on 16S rRNA gene and all isolates amplified 429 bp fragment. To sequence 16S rRNA gene of Shiraz isolates, the universal primer PS16Sf-FAM/PS23Sr was used to amplify 16S rRNA gene. The Iranian isolates of Pseudomonas meliae showed 99.7% similarity to P. meliae (type strain) in the Gene Bank. Based on the rep-PCR results and sequence of 16S rRNA gene, Pseudomonas syringae and Pseudomonas fluorescens were placed in the different groups.     

大型和小型萼花臂尾轮虫的遗传和生活史特征比较研究

近年来，有关生物个体大小变异规律的研究已经成为生活史对策研究的重要内容之一。研究发现，大小相似的萼花臂尾轮虫（Brachionus Calyciflorus）母体所产休眠卵孵化出的不同克隆后代个体大小变化显著，其中，最大个体是最小个体体积的6.25倍。推测种群内产生不同大小的后代个体是轮虫应对环境变化的一种适应性进化策略，然而目前对上述不同大小轮虫克隆的遗传和生活史特征的研究尚未见报道。以mtDNA COI基因和rDNA ITS序列作为分子标记，比较了个体大小差异显著的不同克隆萼花臂尾轮虫的遗传分化程度和分类地位，并在不同温度（20℃、25℃、30℃）和不同斜生栅藻（Scenedesmus obliquus）食物密度（1.0×10⁶、3.0×10⁶、5.0×10⁶个/mL）下比较了它们的生活史特征。结果表明，萼花臂尾轮虫种群内个体大小变异并非由于遗传特征的明显分化所导致，大型和小型个体轮虫克隆在两种分子标记上并不构成姐妹种，且两种形态型间还存在共享单倍型。温度、食物密度、轮虫形态型，以及温度和食物密度各自与轮虫形态型之间的交互作用，均显著影响轮虫的生活史特征。小型轮虫在1.0×10⁶个细胞/mL食物密度下显著延长了胚胎和幼体的发育时间，缩短了生殖期历时；大型轮虫在1.0×10⁶个细胞/mL和3.0×10⁶个细胞/mL食物密度下显著延长了幼体的发育时间，但是其用于胚胎发育和生殖的时间却不随食物密度的变化而变化。各温度和食物密度条件下，大型轮虫的生殖期历时、平均寿命和世代时间均显著延长，或有延长趋势；而两者的种群增长能力之间的差异却因温度和食物密度的不同而异。20℃、25℃以及3.0×10⁶个细胞/mL和5.0×10⁶个细胞/mL食物密度下两种形态型轮虫的生殖能力相似；30℃条件下小型轮虫的生殖能力更强；1.0×10⁶个细胞/mL食物密度下大型轮虫的生殖能力更强。小型轮虫在各温度和各食物密度下均未产生混交雌体后代，而大型轮虫在20℃低温下有较高的后代混交率。因此，大型和小型个体轮虫克隆具有显著不同的生活史策略，且利用有性生殖直接产生个体体积明显变异的不同克隆后代是萼花臂尾轮虫适应不可预测环境变化的一种"赌注策略"。     

乙型脑炎病毒NS2A-C60A位点突变对其生物学特性影响研究*

目的:旨在探索Ⅰ型日本乙型脑炎病毒传代致弱后基因组突变NS2A-C60A对乙脑病毒生物学特性的影响。方法:首先通过对传代致弱及原始乙脑毒株基因组序列进行测序比对、结构预测分析并利用Western blotting(WB)确定了目标研究位点NS2A-C60A;然后使用反向遗传定点突变技术构建拯救了包含NS2A-C60A单点突变的病毒株;最后利用噬斑形态观察、生长曲线、双萤光素酶分析,WB以及炎性因子检测和动物实验研究了该单点突变对于乙脑病毒生物学特性的影响。结果:首次研究发现Ⅰ型乙脑病毒传代致弱会导致NS1'蛋白表达的显著下降以及可能的相关位点NS2A-C60A,并成功拯救获得了NS2A-C60A单点突变毒株rJEV-C60A,研究发现NS2A-C60A突变对乙脑病毒的生长特性及噬斑形成没有显著影响,但是能够显著降低乙脑病毒NS1'蛋白的表达,并且该位点突变能够轻微阻碍乙脑病毒对细胞炎性因子表达的抑制,动物实验结果显示NS2A-C60A点突变病毒与原毒株具有相似的神经毒力,说明该位点突变不是影响乙脑病毒毒力致弱的关键位点。结论:新发现的NS2A-C60A位点突变能够显著减少乙脑病毒NS1'蛋白的表达,但是对其增殖、诱导炎症及神经毒力等生物学特性没有显著影响。     

Strength and Leaching Characteristics of Magnesium Phosphate Cement-Solidified Zinc- Contaminated Soil under the Effect of Acid Rain

Long-term static leaching experiments were conducted to investigate characteristics of magnesium phosphate cement (MPC) solidified/stabilized Zn-contaminated soil under impact of acid rain. Effects of initial pH values of acid rain, binder agent types and compositions, as well as curing age on strength and leaching characteristics of the sample were analyzed. Standard sand was used as raw material, with the content of cement at 15%. Our study used two types of MPC with MgO/KH₂PO₄(M/P) ratio of 3:1 and 6:1 (respectively referred to as M3 and M6), and also ordinary Portland cement with content at 15% (referred to as C15) as test control. Experimental results show that acid rain with pH = 2 has the greatest weakening effect on unconfined compressive strength (q_u) of the sample, while with pH = 4 and 7 such weakening effects on q_u are similar. Research findings also indicate that M6 is the most effective in immobilizing Zn-spiked soils, M3 is next and C15 is the least. The effect of Zn²⁺ on hydration of MPC is much lower than that of C15. Precuring method can improve q_u of the MPC-solidified samples and its resistance to acid rain. Compared with non-renewal, replacing acid rain leachant at designated intervals decreases q_u of the sample.     

Experimental study of the spray characteristics of biodiesel based on inedible oil

We studied the spray characteristics of inedible oil using experimental and simulation methods. Spray penetration, spray cone angle and spray tip speed were measured at different biodiesel ratios in a constant volume vessel with wide visualization and high back pressure, using a high-speed camera. The characteristics of biodiesel spray were simulated under the same conditions using Star-CD software. The experimental results showed that, as the ratio of biodiesel in the blends increased, spray penetration and spray speed increased, but the spray cone angle decreased. Throughout the spray injection period, the region at 0.05–0.475S (spray tip penetration) was a key area affecting spray cone angle. From 0.8 ms after injection, the spray penetration deviation ratios started to increase with increasing biodiesel blend ratios. Simulation results showed similar macroscopic spray characteristics to the experimental results for jatropha oil. The results also showed that the Sauter mean diameter of blend fuels was greater than that of diesel, and spray was more concentrated, due to the higher viscosity and surface tension of the biodiesel, compared with conventional diesel fuel. The macroscopic and microscopic spray properties of blended fuels containing 5%, 10% and 20% biodiesel were similar to diesel.