Succession and phylogenetic profile of eukaryotic communities in rice straw incorporated into a rice field: Estimation by PCR-DGGE and sequence analyses

Abstract

Succession and the phylogenetic profile of eukaryotic communities associated with rice straw decomposition in a rice field were studied using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis followed by 18S rDNA sequencing. Nylon mesh bags containing leaf sheaths or blades were buried in the plow layer of a rice field under flooded conditions after transplanting (Experiment 1) and under drained conditions during the off-crop season (Experiment 2). In addition, rice straw samples in Experiment 2 were taken out before plowing in spring and re-placed in the rice field under flooded conditions at transplanting. Statistical analyses based on DGGE patterns showed that eukaryotic communities were divided into two groups, namely group A before the placement in soil, after the mid-season drainage in Experiment 1 and under the drained conditions in Experiment 2 and group B before the mid-season drainage in Experiment 1 and under the flooded conditions in Experiment 2. Based on the sequence analysis of DGGE bands, which characterized the eukaryotic communities, succession of the communities was revealed, that is, most of the bands in group A were closely related to fungi, whereas the bands in group B were closely related to protozoa. These results indicated that eukaryotic communities associated with rice straw decomposition in the rice field are mainly affected by soil conditions, such as oxic or reduced conditions, irrespective of rice straw parts (leaf sheaths and blades).     

一种改进的基于混沌吸引子的径流降尺度分析

基于混沌理论，研究水文科学的尺度问题，将混沌分析方法应用于径流的降尺度计算。通过分析大时间尺度的年径流量分解到小时间尺度的月径流量的分解系数的混沌特征量，论证了分解系数具有混沌特性。在此基础上，对分解系数的预测方法提出改进意见并给出具体算法。然后根据预测结果进行月径流量的降尺度计算。实例研究表明，改进的算法用于径流量的降尺度分析具有明显的优点。     

不同抗生素对生姜组织培养中姜芽脱菌效果的研究

以PDA和Plate Count Agar作为基本培养基,外加不同浓度配比抗菌素进行脱菌。结果表明：以PDA125 mL作为基本培养基外加1 g/L黄连素10 mL、1 g/L卡那霉素10 mL和外加1 g/L黄连素10 mL、1 g/L多菌灵10 mL,姜块脱菌试验染菌率为0,脱菌效果良好。以PDA125 mL作为基本培养基外加1 g/L青霉素10 mL、1 g/L卡那霉素10 mL,姜芽脱菌试验染菌率为0,脱菌效果良好,另外整个试验过程姜芽的脱菌效果均优于姜块的脱菌效果。     

热水溶出茧层丝胶蛋白的结构变化

对不同时间热水溶出的茧层丝胶的氨基酸组成、热分解温度和分子结构等进行了测定分析．结果表明，随着热水溶出时间的延长，茧层丝胶蛋白中的酸性氨基酸因易溶于水而略有下降，热分解温度因受取向性、结晶性的影响而有所增高，分子结构也由无规则卷曲转化为β构象．丝胶蛋白被降解而成分子大小不一的混合类型     

智能化纳米释药系统用于细菌感染治疗的研究进展

细菌耐药性的相关研究已成为多学科交叉研究的热点,纳米技术因其独特的物化性质在药物递送系统(drug delivery systems,DDSs)的应用中具有可以改善药物的药代动力学和药效学特性,为应对全球细菌抗生素耐药性问题提供了一种新的策略。作为药物载体,理想的纳米粒子必须具有较高的载药量,将药物运送到特定的病理部位和(或)靶细胞,同时不发生药物泄漏,并且在作用部位迅速释放药物。为此,人们积极寻求各种"智能"纳米释药系统,这种纳米释药系统可以对内部或外部刺激(如pH、氧化还原、温度、磁和光等)进行响应,从而实现对药物的可控释放。本文围绕pH、温度、光照以及酶和其他内源或外源因子刺激响应的智能化抗菌药物递送系统领域的最新研究进展进行了评述。     

Upscaling as ecological information transfer: a simple framework with application to Arctic ecosystem carbon exchange

Transferring ecological information across scale often involves spatial aggregation, which alters information content and may bias estimates if the scaling process is nonlinear. Here, a potential solution, the preservation of the information content of fine-scale measurements, is highlighted using modeled net ecosystem exchange (NEE) of an Arctic tundra landscape as an example. The variance of aggregated normalized difference vegetation index (NDVI), measured from an airborne platform, decreased linearly with log(scale), resulting in a linear relationship between log(scale) and the scale-wise modeled NEE estimate. Preserving three units of information, the mean, variance and skewness of fine-scale NDVI observations, resulted in upscaled NEE estimates that deviated less than 4% from the fine-scale estimate. Preserving only the mean and variance resulted in nearly 23% NEE bias, and preserving only the mean resulted in larger error and a change in sign from CO₂ sink to source. Compressing NDVI maps by 70–75% using wavelet thresholding with the Haar and Coiflet basis functions resulted in 13% NEE bias across the study domain. Applying unique scale-dependent transfer functions between NDVI and leaf area index (LAI) decreased, but did not remove, bias in modeled flux in a smaller expanse using handheld NDVI observations. Quantifying the parameters of statistical distributions to preserve ecological information reduces bias when upscaling and makes possible spatial data assimilation to further reduce errors in estimates of ecological processes across scale.     

梨果实在贮藏过程中果胶分解酶活性的变化

以苹果梨和新高梨为试材,测定了梨贮藏过程中果胶分解酶的活性变化.结果表明:2品种果实在软化过程中多聚半乳糖醛酸酶(PG)活性均增加且在贮藏后期新高梨的PG活性极显著(p<0.01)高于苹果梨;贮藏性强的苹果梨的β-半乳糖苷酶(β-Gal)活性很低且在贮藏中减少,但贮藏性相对较弱的新高梨的β-Gal活性极显著(p<0.01)高于苹果梨且在可溶性果胶增加的时期达活性高峰;苹果梨的果胶甲基酯酶(PME)活性在贮藏后期有所增加,但新高梨减少.可见,在贮藏过程中PG和β-Gal酶均是梨果实软化的重要酶,但β-Gal的作用比PG酶更重要;PME的活性变化因品种而异,与耐贮性关系不大.     

鳞毛蕨(Dryopteris filix-mas)天山云杉林倒木更新分析

对西天山国家级自然保护区1 hm2典型鳞毛蕨天山云杉林临时标准地内,倒木对更新的影响进行了研究.结果表明:①研究区中所有倒木的平均倾倒方向为西北方向,具有更新个体存在的倒木平均倾倒方向为东北方向;②倒木的倾倒方向对倒木的更新没有显著影响(F3,51=0.645,P=0.589),而倒木的腐朽等级对倒木的更新存在显著影响(F2,51=3.215,P=0.048);③不同腐朽等级倒木上幼苗、幼树的出现概率不同,能为幼苗、幼树生长提供生境的倒木只有腐朽等级高的Ⅲ,Ⅳ,Ⅴ级倒木,且倒木腐朽等级越高,对幼苗、幼树的生长越有利.     

关于兽用抗菌药使用减量化行动的探索与实践

宁夏以兽药生产经营使用环节全链条监管、动物源细菌耐药性监测技术体系建立、养殖场生物安全体系构建、减抗替抗产品推广应用、示范点带动等重点工作为切入点,强化质量保障,重视创新驱动,构建“政府+企业”产学研合作机制,不断促进兽用抗菌药使用减量化,形成了一套“监管到位、技术保障、企业尽责、用药减量”的兽用抗菌药使用减量化技术推广模式。     

紫云英腐解液对牛筋草种子萌发及幼苗生长的影响

为探讨不同腐解天数及不同浓度梯度紫云英的腐解液对牛筋草种子萌发及二叶期幼苗生长的影响,以牛筋草种子为材料进行发芽试验,测定发芽率等6个生理指标。采用不同浓度的紫云英腐解液对二叶期幼苗进行灌根处理,测定牛筋草叶片的保护酶活性、脯氨酸（Pro）和丙二醛（MDA）含量。结果表明：相同浓度腐解液处理条件下,随着腐解天数的增加,腐解液对牛筋草的抑制作用增强;腐解液对牛筋草的化感作用存在“低促高抑”的现象;当腐解时间超过2 d,腐解液处理浓度达到80%时,能100%抑制牛筋草种子萌发。牛筋草幼苗的超氧化物歧化酶（SOD）活性随着腐解液浓度升高而下降;过氧化物酶（POD）在低浓度腐解液处理时酶活性下降,浓度大于30%时酶活性升高;过氧化氢酶（CAT）活性在30%腐解液浓度内随着浓度升高而升高,80%时活性下降。当腐解液浓度≥2%时,随着腐解液浓度的增加,牛筋草叶片MDA、Pro及过氧化氢（H₂O₂）含量增加。综上所述,紫云英腐解液对牛筋草种子萌发及幼苗生长具有显著的抑制作用。由此可见,紫云英腐解物具有抑制杂草生长的潜力,研究结果可为发掘紫云英中抗杂草活性物质提供参考。