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1.
目的 建立鸡沙门菌287/91株的基因组物理图,与鸡沙门菌SARB21以及鼠伤寒沙门菌LT2的基因组物理图进行比较,以找出同种细菌不同菌株之间以及近缘菌之间基因组的差异,进而探讨细菌基因组进化的一般规律。方法 细菌基因组DNA用XbaⅠ、AvrⅡ和bCeuⅠ进行酶切,再用脉冲场凝胶电泳方法分离出DNA片段,通过Tn10插入等方法对这些片段进行精确排列。结果 构建了鸡沙门菌287/91株的基因组物理图。与SARB21株的基因组物理图比较发现,二者相对于鼠伤寒沙门菌LT2有相似的插入和缺失片段。结论 鸡沙门菌287/91株与SARB21株基因组很相似,其主要差异在于rrn操纵子DNA介导的同源性重组发生的具体部位不同,导致了基因组DNA片段的不同排列,因而造成二者不同的基因组结构。  相似文献   

2.
细菌进化中的基因横向转移   总被引:1,自引:0,他引:1  
越来越多的证据表明,通过横向基因转移(lat eralgenetransfer ,LGT)而获得外源DNA是细菌中的普遍现象,在很多情况下,有可能是细菌进化的关键因素〔1 12〕。随着基因组序列信息的大量增加和基因芯片等基因组学技术的不断进步,人们已经能够追踪亲缘关系较近的细菌中某些基因的出现、消失与再现,从而探讨细菌基因组进化的一些基本规律。近年来这方面研究在沙门菌(Salmonella)属的细菌中多有报道〔6,12 2 0〕。沙门菌属的细菌虽然在遗传上互相非常接近,但是在宿主和临床表现上可有很大差异,因此,特别适合于细菌基因组进化的研究。3株沙门菌…  相似文献   

3.
目的 分析保守序列CTAG在S.typhimurium DT 104的含量及分布情况,比较4个主要插入片段之间的相对进化时间规律,探究在所有沙门菌全基因组中CTAG所反映出的进化关系.方法 统计S.typhimurium DT104菌株4个插入片段(ST64B、ST104、ST104B及SGI1)的位置、CTAG含量及分布规律.将NCBI中下载的32株目的菌株分为3个水平,通过基因组序列比对方式统计其共有的保守序列CTAG所在位置及功能注释,结合菌株间进化关系加以分析.结果 保守序列CTAG在整个基因组进化中不断被清除,插入片段中CTAG分布频率较原基因组更高,且存在由中间向两端逐渐减少的趋势.沙门菌全基因组中尚存的CTAG所在位置涉及进化过程中的重要功能.结论 CTAG在沙门菌进化中为适应生存需要整体呈退化趋势,其含量及分布规律可以反映插入片段相对进化时间的远近.CTAG在细菌基因组进化过程中高度保守,可作为相关研究的补充衡量指标.  相似文献   

4.
细菌、果蝇和人的染色体重复   总被引:1,自引:0,他引:1  
本文综述了细菌、果蝇和人的染色体重复,总结了染色体重复的一般特征.指出染色作片段的串联重复是一种常见的突变机制。同时,染色体重复及由其导致的基因重复是基因组进化的普遍特征,并被看作是新的基因功能产生和适应性进化的主要机制.  相似文献   

5.
细菌,果蝇和人的染色体重复   总被引:1,自引:0,他引:1  
本文综述了细菌、果蝇和人的染以体重复,总结了染色体重复的一般特征。指出染色体片段的串联重复是一种常见突变机制。同时,染色体及人导致的基因重复是基因组进行化的普遍特征,并被看作是新的基因功能产生和适应性进化的主要机制。  相似文献   

6.
目的:从进化的角度研究古菌、细菌和真核生物基因组中密码对的使用,得到密码对使用与生物进化的可能的规律。方法:生物统计学。结果:首先,比较了编码序列中密码对出现频数的观测值与理论值之差的分布,发现这种分布基本是随机的;其次,这个分布也表明密码对的使用普遍具有偏好性,且不同物种所偏好的密码对和偏好的程度是不同的;第三,终止密码对的使用也存在偏好性,对于同一个密码子与不同的终止密码组合时,其观察值与理论值的关系依赖于终止密码子的类型。结论:结果表明密码对的使用与基因组进化存在相关性。  相似文献   

7.
耐药性播散机制进展——整合子-基因匣子系统   总被引:2,自引:0,他引:2  
整合子 -基因匣子系统是近年在细菌中发现的天然克隆与表达系统 ,能捕获外来耐药基因 ,在整合子中形成多种耐药基因的组合、排列 ,是细菌耐药性播散的机制之一 ,对细菌及质粒基因组的进化具有重要意义。本文对整合子 -基因匣子系统的结构特征、基因匣子的移动性与表达、整合子的流行病学及超整合子等方面进行综述。  相似文献   

8.
背景:有研究表明,不同试剂盒提取的粪便细菌基因组DNA质量有差别,选择一种操作简便、质量优良的粪便细菌基因组DNA提取试剂盒成为研究者们关注和急需解决的问题。 目的:比较QIAamp及Biomed粪便细菌基因组DNA提取试剂盒提取的人肠道细菌基因组DNA质量的差异。 方法:收集健康成年人新鲜粪便标本30例,用两种试剂盒分别提取细菌基因组DNA,检测其浓度、吸光度A260/280 nm值及提取率,设计乳酸菌属16S rDNA基因特异性引物,以各自所提DNA为模板,进行常规聚合酶链反应,凝胶电泳后比较条带数量、明暗度及密度,并进行实时荧光定量聚合酶链反应定量检测各自所含乳酸菌属的数量。 结果与结论:QIAamp试剂盒提取的正常人肠道细菌基因组DNA的浓度、提取率、表达量及乳酸菌属的数量均高于Biomed试剂盒(P < 0.05或P < 0.01)。说明QIAamp试剂盒提取的粪便细菌基因组DNA质量优于Biomed试剂盒。  相似文献   

9.
  美国 Baylor 医学院 George Weinstock博士领导的恒河猴基因组成功破译出了猕猴的基因组,这是继人类和黑猩猩之后,科学家破译出的第 3 种灵长类动物基因组。今年 4 月13日出版的 Science 以封面文章形式发表了这项最新成果。研究结果证实,虽然早在约 2.5 亿万年前,恒河猴从向人类进化的灵长类动物中分离出来,但人类和恒河猴基因组仍有93%的同源性。此项研究将有助于科学家进一步探索人类与恒河猴相似性及差异性背后的遗传学基础。通过比较人类和恒河猴基因组的异同可以获得许多有意义的结果。 从医学研究的角度,由于恒河猴常用于实验性药物及治疗方案的研究,明确恒河猴与人类基因水平的差异,有助于更好地预计一种药物在人体上产生的效果是否有别于动物实验的结果。研究者还指出,尤其在免疫系统方面,人类和恒河猴的众多基因类型存在显著差别。通过研究这些差别,如何使用恒河猴动物模型作为人类疾病研究的替代品将得到进一步的调整和优化,从而提高灵长类动物实验结果对人体试验的参考价值。此外,研究者还发现,和人类基因组相比,对于糖类消化极其重要的一种基因在恒河猴基因组中被大量扩增。研究者猜测这一基因水平的适应使得恒河猴可以摄入含有大量水果及糖分的饮食。 恒河猴基因组测序的完成还为其他灵长类动物和人类基因组比较提供了一个新的参考依据。早在 2005 年,科学家完成了一种更为接近人类的灵长类动物--猩猩的基因组测序,结果显示猩猩的基因组与人类基因组有 98% 的同源性。如果科学家发现人类和猩猩的某种基因存在不同,可以通过与恒河猴基因组比较以判断谁携带了更古老的基因。通过进行类似的比较,科学家希望能够确定基因组中参与人类进化的特定区域。在未来的几年内,随着更多非人类灵长类动物基因组测序的完成,将使得这一方法得到更广泛的应用。  相似文献   

10.
23S rRNA基因序列分析及其在细菌鉴别诊断中的应用   总被引:9,自引:0,他引:9  
目的研究细菌23S rRNA基因序列的差异,为细菌鉴别诊断和相关研究提供科学依据。方法设计合适的通用引物、寻找恰当的扩增条件扩增常见细菌的23S rRNA基因片段。通过序列测定和运用生物信息学分析不同种属细菌23S rRNA基因的保守序列、变异规律及菌株间种系进化关系。结果扩增出常见引起食源性感染的16属(种)细菌23S rRNA基因片段。部分扩增产物进行了限制性酶切鉴定和序列测定。序列比较研究获得21个23S rRNA的通用保守序列,23S rRNA基因保守序列与变异区在种系间呈间隔分布,大量变异区呈“马赛克”式分布。种系间进化关系与16S rRNA分析结果一致。结论23S rRNA基因序列的分布规律为进行细菌的鉴别诊断及基因芯片的研制提供了重要的理论和实验基础。  相似文献   

11.
The general principles of structural and functional organization of genomes in pathogenic bacteria are considered. Main data on the specific features of genomes of Chlamydia trachomatis, Rickettsia prowazekii, Treponema pallidum, Helicobacter pylori, Haemophilus influenzae, Neisseria meningitidis, Vibro cholerae and pathogenic strains of Escherichia coli are summarized. Particular attention is paid to the problems of genetic control of pathogenicity, intraspecies variations in bacterial genomes, to the environmental and evolutionary meaning of horizontal gene transfer. Whether methods for genotyping bacterial strains can be used is discussed.  相似文献   

12.
As genomes evolve, they undergo large-scale evolutionary processes that present a challenge to sequence comparison not posed by short sequences. Recombination causes frequent genome rearrangements, horizontal transfer introduces new sequences into bacterial chromosomes, and deletions remove segments of the genome. Consequently, each genome is a mosaic of unique lineage-specific segments, regions shared with a subset of other genomes and segments conserved among all the genomes under consideration. Furthermore, the linear order of these segments may be shuffled among genomes. We present methods for identification and alignment of conserved genomic DNA in the presence of rearrangements and horizontal transfer. Our methods have been implemented in a software package called Mauve. Mauve has been applied to align nine enterobacterial genomes and to determine global rearrangement structure in three mammalian genomes. We have evaluated the quality of Mauve alignments and drawn comparison to other methods through extensive simulations of genome evolution.  相似文献   

13.
Recent advances in sequencing of complete bacterial genomes, molecular typing of micro-organisms, and research on microbial pathogenicity factors changed our view on the evolution of human bacterial pathogens. We review current evolutionary concepts on plague and meningococcal disease to illustrate the interplay of molecular phylogeny, epidemiology, and pathogenicity research. Furthermore, examples of the tremendous velocity of bacterial evolution under changing environmental conditions will be discussed.  相似文献   

14.
Most recently published complete bacterial genomes have revealed unexpectedly high numbers of long strict repeats. In this article we discuss the various functional and evolutionary roles of these repeats, focusing in particular on their role in terms of genome stability, gene transfer, and antigenic variation.  相似文献   

15.
Reconstructing the evolutionary history of all species is an essential objective for evolutionary biologists. Much effort has been devoted to ancestral genome reconstruction. Numbered genome sequencing of current and extinct organisms enables evolutionary biologists to compare genomic data and reconstruct ancestral genomes. Long-term conservation of karyotype, gene order or gene sequence are clues to the heritage of each species and these data can be used by evolutionary biologists to synthesize distant ancestral genomes. In this review, we referred to the recent advances in ancestral genomes reconstruction and the insight it gives on genome evolution. Special attention is devoted to the use of this knowledge to understand the evolution of the immune system genes.  相似文献   

16.
Gene order in prokaryotes is conserved to a much lesser extent than protein sequences. Only several operons, primarily those that code for physically interacting proteins, are conserved in all or most of the bacterial and archaeal genomes. Nevertheless, even the limited conservation of operon organization that is observed can provide valuable evolutionary and functional clues through multiple genome comparisons. A program for constructing gapped local alignments of conserved gene strings in two genomes was developed. The statistical significance of the local alignments was assessed using Monte Carlo simulations. Sets of local alignments were generated for all pairs of completely sequenced bacterial and archaeal genomes, and for each genome a template-anchored multiple alignment was constructed. In most pairwise genome comparisons, <10% of the genes in each genome belonged to conserved gene strings. When closely related pairs of species (i.e., two mycoplasmas) are excluded, the total coverage of genomes by conserved gene strings ranged from <5% for the cyanobacterium Synechocystis sp to 24% for the minimal genome of Mycoplasma genitalium, and 23% in Thermotoga maritima. The coverage of the archaeal genomes was only slightly lower than that of bacterial genomes. The majority of the conserved gene strings are known operons, with the ribosomal superoperon being the top-scoring string in most genome comparisons. However, in some of the bacterial-archaeal pairs, the superoperon is rearranged to the extent that other operons, primarily those subject to horizontal transfer, show the greatest level of conservation, such as the archaeal-type H+-ATPase operon or ABC-type transport cassettes. The level of gene order conservation among prokaryotic genomes was compared to the cooccurrence of genomes in clusters of orthologous genes (COGs) and to the conservation of protein sequences themselves. Only limited correlation was observed between these evolutionary variables. Gene order conservation shows a much lower variance than the cooccurrence of genomes in COGs, which indicates that intragenome homogenization via recombination occurs in evolution much faster than intergenome homogenization via horizontal gene transfer and lineage-specific gene loss. The potential of using template-anchored multiple-genome alignments for predicting functions of uncharacterized genes was quantitatively assessed. Functions were predicted or significantly clarified for approximately 90 COGs (approximately 4% of the total of 2414 analyzed COGs). The most significant predictions were obtained for the poorly characterized archaeal genomes; these include a previously uncharacterized restriction-modification system, a nuclease-helicase combination implicated in DNA repair, and the probable archaeal counterpart of the eukaryotic exosome. Multiple genome alignments are a resource for studies on operon rearrangement and disruption, which is central to our understanding of the evolution of prokaryotic genomes. Because of the rapid evolution of the gene order, the potential of genome alignment for prediction of gene functions is limited, but nevertheless, such predictions information significantly complements the results obtained through protein sequence and structure analysis.  相似文献   

17.
An unusually high proportion of proteins encoded in Chlamydia genomes are most similar to plant proteins, leading to proposals that a Chlamydia ancestor obtained genes from a plant or plant-like host organism by horizontal gene transfer. However, during an analysis of bacterial-eukaryotic protein similarities, we found that the vast majority of plant-like sequences in Chlamydia are most similar to plant proteins that are targeted to the chloroplast, an organelle derived from a cyanobacterium. We present further evidence suggesting that plant-like genes in Chlamydia, and other Chlamydiaceae, are likely a reflection of an unappreciated evolutionary relationship between the Chlamydiaceae and the cyanobacteria-chloroplast lineage. Further analyses of bacterial and eukaryotic genomes indicates the importance of evaluating organellar ancestry of eukaryotic proteins when identifying bacteria-eukaryote homologs or horizontal gene transfer and supports the proposal that Chlamydiaceae, which are obligate intracellular bacterial pathogens of animals, are not likely exchanging DNA with their hosts.  相似文献   

18.
Evidence has shown that bacterial genomes have undergone random shuffling of genomic elements consisting of one to two genes. In order to delineate such genome-shuffling events in mammals, we constructed a high-resolution map of Sus scrofa chromosome 3 (SSC3) with a total of 116 genes/markers. Alignment of this pig map to orthologous regions in human, dog, mouse and rat led to the identification of 31 provisional conserved ancestral blocks (CABs) in these five species. Among them, only 3 CABs (<10%) had one gene, indicating that one-gene shuffling is not frequent in mammals. The sizes of CABs vary significantly within a species, but each may be relatively consistent in different species with a scale to species-genome evolution. The type and frequency of rearrangement events that takes place, either intra- or interchromosomal, depends on the evolutionary regions and species under comparison. Characterization of 36 tentative breakpoint regions flanking these 31 CABs indicated that they occupied ∼43 Mb in length and featured genome deserts, gene duplications, and birth/death of species-specific genes in humans. Identification of CABs provides an alternative for further determination of the evolutionary make-up of mammalian genomes.  相似文献   

19.
Although the members of the Herpesvirus family are responsible for a wide variety of human diseases, advances in the understanding of viral molecular mechanisms of pathogenesis have been hampered by the large size of herpesvirus genomes, rendering the viruses difficult to experimentally manipulate. Better techniques have been needed to facilitate mutagenesis of herpesvirus genomes, allowing for the assessment of the role of specific viral gene products in replication, immunity, and pathogenesis. Homologous recombination with plasmids containing genes of interest flanked by selectable markers has been a successful method for generating viral mutants, as has the generation of recombinant virus from transfection of cosmid clones. Although these efforts to generate recombinant viruses have met with modest success, the protocols have been cumbersome. More recently, a novel technique for the manipulation of herpesvirus genomes has been developed. This technology utilizes bacterial F plasmids, and allows for the stable cloning of herpesvirus genomes as bacterial artificial chromosomes (BACs) in Escherichia coli. Once cloned, such BACs are stable, and DNA purified from E. coli is infectious, fully capable of reproducing replication-competent virus. Manipulation of herpesvirus genomes is now feasible using the powerful techniques of bacterial genetics, and should facilitate a better understanding of the molecular pathogenesis of herpesvirus infections.  相似文献   

20.
A model to explain the evolutionary history of animal-bacteria obligatory mutualistic symbiosis is presented. Dispensability of genes and genetic isolation are key factors in the reduction process of these bacterial genomes. Major steps in such genome reductive evolution, leading towards primary endosimbiosis, and the possibility of complementation or replacement by a secondary symbiont are also indicated. Yet, we need to understand what happens at the beginning of the adaptative process towards an obligate mutualistic relationship. For this purpose, we propose to sequence the complete genome of SOPE, the primary endosymbiont of the rice weevil.  相似文献   

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