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141.
Abstract A highly sensitive nested polymerase chain reaction method was designed for the detection of a wide spectrum of strains from Borrelia burgdorferi sensu lato. This technique allows the detection of as little as 3 fg of total genomic DNA extracted and purified from pure cultures of the organism, this amount corresponds to less than 10 organisms. Two sets of primers homologous to conserved spots in the coding region of the hbb gene, encoding a conserved histone-like protein, were constructed. These were based on a multiple sequence alignment of 39 strains representing all the genomic groups described in B. burgdorferi sensu lato.  相似文献   
142.
Apioceridae (Insecta: Diptera): cladistic reappraisal and biogeography   总被引:1,自引:0,他引:1  
Twenty members of the fly families Apioceridae and Mydidae are compared in terms of 77 adult characters. Cladistic analysis of 91 synapomorphies provides a well corroborated reconstruction of lineage relationships, and reveals that the Apioceridae is paraphyletic with respect to the Mydidae. In order to render the Apioceridae monophyletic, the genus Rhaphiomidas and the subfamily Megascelinae of the Apioceridae are transferred to the Mydidae. The subfamily Rhaphiomidinae is reinstated to accommodate Rhaphiomidas , comprising the most plesiomorphic mydids. The relationships of the remaining subfamilies of Mydidae are discussed in the context of these findings. The genus Apiocera is divided into four subgenera, the type subgenus Apiocera Westwood in Australia, Pyrocera subgen. nov. in North America, and the subgenera Ripidosyrma Hermann and Anypenus Philippi are applied to the South African and South American species, respectively. A key to the four subgenera of Apiocera is provided. The biogeographic relationships of the subgenera and genera of the Apioceridae and the Megascelinae are discussed. Although considered an example of a transantarctic or Gondwanan group, we argue that the distribution of the Apioceridae predates the Mesozoic supercontinent Gondwanaland and extends onto sections of Pangaea, and should be termed 'Pangaean'. The cladistic relationships between the genera of Apioceridae and Megascelinae are consistent with the geological vicariance of the fragments of Pangaea on which they now occur.  相似文献   
143.
【目的】滨海湿地生态系统位于淡水与海水交互地带,含有高浓度Fe2+的地下水渗透到沉积物表层形成的湿地径流和周期性潮汐淹水形成的含氧-缺氧界面有利于铁氧化细菌介导的Fe2+的生物氧化过程发生。然而,目前缺乏对滨海湿地生态系统中铁氧化细菌类群的全面评估。【方法】以上海崇明西沙湿地公园及浙江舟山市朱家尖岛东沙沙滩两地共5处滨海湿地沉积物为研究对象,分析沉积物的氧气穿透深度等环境参数,并基于16S rRNA基因扩增子测序技术,全面解析不同滨海湿地生态系统中细菌与铁氧化细菌的群落组成与分布特征。【结果】与崇明西沙湿地相比,朱家尖岛东沙沙滩有更深的氧气穿透深度,达到10 mm以上。非度量多尺度分析(non-metric multidimensional scaling, NMDS)统计结果表明,细菌群落结构主要受到区域位置不同导致的环境条件差异的影响,而铁氧化细菌的群落结构则受到采样的区域位置和沉积物氧气穿透深度的共同影响。崇明西沙湿地和朱家尖岛东沙沙滩的优势细菌为蓝细菌门(Cyanobacteria)、γ-变形菌纲(Gammaproteobacteria)、拟杆菌门(Bacteroidetes)、α-变形菌纲(Alphaproteobacteria)和放线菌门(Actinobacteria);优势铁氧化细菌为嘉利翁氏菌属(Gallionella)、红细菌属(Rhodobacter)、LepthothrixSideroxydans。【结论】通过对崇明西沙湿地和朱家尖岛东沙沙滩沉积物中栖息的铁氧化菌的调查发现,铁氧化细菌的群落组成与湿地沉积物类型导致的氧气穿透深度差异具有密切联系。  相似文献   
144.
蛋白质折叠规律研究是生命科学领域重要的前沿课题之一,蛋白质折叠类型分类是折叠规律研究的基础。本研究以SCOP数据库的蛋白质折叠类型分类为基础、以Astral SCOPe 2.05数据库中相似性小于40%的α、β、α+β及α/β类所属的折叠类型为研究对象,完成了989种蛋白质折叠类型的模板构建并形成模板数据库;基于折叠类型设计模板建立了蛋白质折叠类型分类方法,实现了SCOP数据库蛋白质折叠类型的自动化分类。家族模板自洽性检验与独立性检验所得的敏感性、特异性以及MCC的平均值分别为:95.00%、99.99%、0.94与90.00%、99.97%、0.92,折叠类型模板自洽性检验与独立性检验所得的敏感性、特异性以及MCC的平均值分别为:93.71%、99.97%、0.91与86.00%、99.93%、0.87。结果表明:模板设计合理,可有效用于对已知结构的蛋白质进行分类。  相似文献   
145.
蛋白质折叠规律研究是生命科学重大前沿课题,折叠类型分类是蛋白质折叠研究的基础。构建BRD-like折叠类型模板数据库,建立了基于多模板的综合分类方法,并用于该折叠类型的分类。对实验集的12 117个样本进行检验,结果的敏感性、特异性分别为0.923和0.997,MCC值为0.72;对独立检验集2 260个样本的检验,结果发现:敏感性、特异性分别为0.941和0.998,MCC值为0.86.结果表明:基于多模板的综合分类方法可用于蛋白质折叠类型分类。  相似文献   
146.
Ontogenic development is divided into infant, juvenile, adolescent and adult life‐stages. Although the developmental trajectory of an individual is a flexible entity, which differs within species, environment and sex, life‐stage classifications are generally structured, age‐based systems. This invariably leads to rigidity within a dynamic system and consequently hampers our understanding of primate life history strategies. We propose that life‐stage classifications should be quantitative, flexible entities, which use a reliable measurement of development. Here, we provide a methodological example where placement into a life‐stage is based upon behavioral variance between other similar‐aged individuals. Behavioral data were collected from 12 male (3–11 years old) and 9 female (3–8 years old) captive immature western gorillas (Gorilla gorilla gorilla) housed in five family groups, using continuous focal sampling; 900 hr of data were collected over 131 days. Data were applied to four published life‐stage classifications for mountain gorillas (Gorilla beringei beringei), which showed variable ability to determine life‐stage in western gorillas. A new life‐stage classification (Hutchinson & Fletcher) was proposed specifically for western gorillas, whereby multiple co‐varying behavior provided a robust measure of linear development across immaturity. Each life‐stage was found to be a distinct ontogenic phase and the classification discriminated life‐stage with a high level of accuracy. Using the Hutchinson & Fletcher classification we provide evidence for disparity in developmental trajectories between the sexes from the juvenile period onwards. To expand the understanding of primate life histories, we propose that flexible classifications should be used to enable comparison of allometric life history traits within and between species, from birth onwards. Am. J. Primatol. 72:492–501, 2010. © 2010 Wiley‐Liss, Inc.  相似文献   
147.
有关物种概念与划分中的一些问题   总被引:2,自引:1,他引:2  
同号文 《古生物学报》1995,34(6):761-776
关于物种的问题已经争论了几百年,但至今仍未达成完全一致,尤其是在物种的概念、物种的划分及物种的形成等主要方面的观点分歧较大,可说是学派林立、百家争鸣。引起这些分歧的根本原因是生物的极端多样性,当然,也与每个人的观察角度和认识水平不无关系。目前,最大的矛盾是,一方面大家竟相给物种想下一个简明而又高度概括的定义,另一方面在实际操作中,对不同生物却是各有其标准。这样就必然产生了很多不同的物种概念,甚至产生了混乱。此外,种下单元的划分,不论在标准还是术语方面,都存在很大问题,尤其是种和亚种的分类及系统关系问题过去和现在都被严重地忽视了。  相似文献   
148.
We used the four redfish taxa (genus Sebastes) from the North Atlantic to evaluate the potential of multilocus genotype information obtained from microsatellites in assigning individuals at two different levels of group divergence. We first tested the hypothesis that microsatellites can diagnostically discriminate individual redfish from different groups. Second, we compared two different methods to quantify the effect of number of loci and likelihood stringency levels on the power of microsatellites for redfish group membership. The potential of microsatellites to discriminate individuals from different taxa was illustrated by a shared allele distance tree in which four major clusters corresponding to each taxa were defined. Concomitant with this strong discrimination, microsatellites also proved to be powerful in reclassifying specimens to the taxon of origin, using either an empirical or simulated method of estimating assignment success. By testing for the effect of both the number of loci and the level of stringency on the assignment success, we found that 95% of all specimens were still correctly reclassified with only four loci at the most commonly used criterion of log0. In contrast, the results obtained at the population level within taxa highlighted several problems of assignment that may occur at low levels of divergence. Namely, a drastic decrease of success with increasing stringency illustrated the lack of power of our set of loci. Strong discrepancy was observed between results obtained from the empirical and simulated methods. Finally, the highest assignment success was obtained when reducing the number of loci used, an observation previously reported in studies of human populations.  相似文献   
149.
CORA is a suite of programs for multiply aligning and analyzing protein structural families to identify the consensus positions and capture their most conserved structural characteristics (e.g., residue accessibility, torsional angles, and global geometry as described by inter-residue vectors/contacts). Knowledge of these structurally conserved positions, which are mostly in the core of the fold and of their properties, significantly improves the identification and classification of newly-determined relatives. Information is encoded in a consensus three-dimensional (3D) template and relatives found by a sensitive alignment method, which employs a new scoring scheme based on conserved residue contacts. By encapsulating these critical "core" features, templates perform more reliably in recognizing distant structural relatives than searches with representative structures. Parameters for 3D-template generation and alignment were optimized for each structural class (mainly-alpha, mainly-beta, alpha-beta), using representative superfold families. For all families selected, the templates gave significant improvements in sensitivity and selectivity in recognizing distant structural relatives. Furthermore, since templates contain less than 70% of fold positions and compare fewer positions when aligning structures, scans are at least an order of magnitude faster than scans using selected structures. CORA was subsequently tested on eight other broad structural families from the CATH database. Diagnostics plots are generated automatically and provide qualitative assistance for classifying newly determined relatives. They are demonstrated here by application to the large globin-like fold family. CORA templates for both homologous superfamilies and fold families will be stored in CATH and used to improve the classification and analysis of newly determined structures.  相似文献   
150.
We developed and tested a quantitative geographic information system (GIS)-based approach for selecting wetland restoration sites. Our approach uses a combination of an existing wetland function evaluation program, a GIS and integer programming methodology with an objective to minimize cost of restoration subject to meet environmental requirements. Investigations were conducted on the formulation to examine the effects of problem size, site ordering for input, and restoration targets. The formulation could be solved for the largest problem size tested of 996 integer variables. The larger the problem, the more time it took to solve. Larger restoration targets usually took more sites and more time to solve. Sorting sites by size was found to lead to inefficient and often unfeasible solutions. Random sorting of sites was found to be the more efficient method of inputting restoration sites into analysis.  相似文献   
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