土壤噬菌体及其介导的抗生素抗性基因水平转移研究进展

土壤中抗生素耐药性的扩散对全球的公共卫生和食品安全造成威胁,严重挑战人类感染类疾病的预防与治疗.噬菌体介导的抗生素抗性基因(ARGs)的水平转移是环境中抗性基因扩散的重要机制.但是,噬菌体对土壤环境中抗性基因传播的贡献尚未见报道.本文综述了土壤环境中噬菌体的分布特征与影响因子,总结了纯化和富集土壤噬菌体的主要研究方法;...     

病毒性载体介导的基因转移研究进展

病毒性载体介基因转移研究进展迅速,并率先用于临床基因治疗试验。目前研究重点在其进一步完善和发展,以及发现新的适于基因治疗的病毒性载体,已获部分突破性进展,大大加速了基因治疗研究的进程,但也存在一些限制因素,尚需深入研究。     

噬菌体整合酶--基因转移的工具酶

噬茵体整合酶是整合位点序列特异性的酶类。由于这一特性,它可用于向染色体定位特异性地导入目的基因,在遗传工程、基因治疗、转基因动物等领域极具应用前景。本文综述噬茵体整合酶的发现与分类、结构与功能及其应用前景。     

痢疾杆菌染色体中噬菌体插入序列的分析

噬菌体作为细菌的病毒通过参与细菌的代谢过程完成自身的繁殖和复制.自80多年前噬菌体被发现以来,噬菌体因其遗传物质和结构组成十分简单并且与宿主细胞相互作用非常密切一直被作为研究生命基本规律的良好的模型系统.     

金黄色葡萄球菌毒力基因的调控位点

金黄色葡萄球菌的许多致病因子受到细菌的多种遗传位点的调控,各调控位点之间存在复杂作用,各位点的突变可降低金黄色葡萄球菌的致病力。     

金黄色葡萄球菌中PVL基因与噬菌体DNA的同源性

为了探讨金黄色葡萄球菌PVL基因与噬菌体的相关性,从4株含有PVL基因的菌株中分离出DNA,用HindⅢ或EcoRI酶切后,分别与PVL和Lukm-lukF-PV探针进行Southern印迹杂交,以及对含有PVL基因及其下游区域的片段克隆、测序和同源性分析。结果表明3株菌的PVL基因及其下游区域的序列与V8菌株噬菌体ΦPVL的PVL基因及其下游噬菌体stt site的序列一致。另一菌株的LukM-lukF-PV基因与ΦPVL,的PVL基因有78％的同源性,并且在LukM-lukF-PV基因的下游区域发现与金黄色葡萄球菌噬菌体Φ11整合位点有98％同源性的序列,根据PVL基因存在于噬菌体的基因组上,推测可通过噬菌体转导在金黄色葡萄球菌中传播。     

幽门螺杆菌毒力基因分型与相关胃病

幽门螺杆菌毒力基因是其致病的原因之一,目前已知的主要毒力基因包cagPAI,vacA,iceA,babA等,不同毒力基因分型及其结合与相关性胃疾病的关系在不同地区报道不同。对幽门螺杆菌毒力基因分型的研究有利于鉴别其毒力菌株,揭示其致病机制及为幽门螺杆菌感染的流行病学研究提供帮助。     

原噬菌体PBSX阻遏基因及其温度敏感型等位基因的克隆分析

本研究利用聚合酶链式反应技术,成功地克隆了枯草芽孢杆菌缺陷型原噬菌体ＰＢＳＸ阻遏基因及其温度敏感型等位基因。核苷酸序列分析发现,野生型及其温度敏感型阻遏基因之间的碱基变异较大,但却存在几乎完全相同的开放读框,尤其是开放读框ｏｒｆⅠ,可能编码着１１３个氨基酸的阻遏蛋白,并且还推定了开放读框的启动区和核糖体结合位点。通过互补实验,证实了野生型阻遏基因的产物能够抑制温度诱导ＰＢＳＸ原噬菌体,表明克隆的基因有着正常的生物活性。     

Phage dUTPases Control Transfer of Virulence Genes by a Proto-Oncogenic G Protein-like Mechanism

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Highlights? dUTPases are signaling molecules acting in analogous manner to the G proteins ? Binding to dUTP induces a conformational change in the phage-encoded dUTPases ? The dUTP-bound form of the phage dUTPases induces transfer of virulence genes ? The dUTPase P loop-like motif V is the molecular switch of the signaling mechanism     

Virulence Gene Regulation by l-Arabinose in Salmonella enterica

Invasion of the intestinal epithelium is a critical step in Salmonella enterica infection and requires functions encoded in the gene cluster known as Salmonella Pathogenicity Island 1 (SPI-1). Expression of SPI-1 genes is repressed by l-arabinose, and not by other pentoses. Transport of l-arabinose is necessary to repress SPI-1; however, repression is independent of l-arabinose metabolism and of the l-arabinose-responsive regulator AraC. SPI-1 repression by l-arabinose is exerted at a single target, HilD, and the mechanism appears to be post-translational. As a consequence of SPI-1 repression, l-arabinose reduces translocation of SPI-1 effectors to epithelial cells and decreases Salmonella invasion in vitro. These observations reveal a hitherto unknown role of l-arabinose in gene expression control and raise the possibility that Salmonella may use L-arabinose as an environmental signal.     

Interrelationship between Colony Type, Phage Susceptibility and Virulence in Xanthomonas oryzae

S ummary : A colonial mutant of Xanthomonas oryzae. (tentatively designated T) had a transparent colony (associated with absence of polysaccharide), resistance to the bacteriophage Bpl and markedly attenuated virulence. Phage resistant mutants with the same colonial characteristics as the wild type (W), which is opaque because of abundant polysaccharides produced, showed various degrees of virulence. Disease symptoms were not suppressed when cells of T were mixed with W in various proportions and used to inoculate rice plants. Disease severity was dependent on the proportion of T in the inoculum and the multiplication of T in the plant was proportional to its initial number of cells in the mixture. When infected rice plants were grown in irrigation water containing phage, little or no selection of phage-resistant mutants was detected in spite of repeated and high selection pressure. This may be explained by an insufficient supply of bacterial cells from diseased leaves into the irrigation water and by the very low propotion of phage-resistant mutants that are virulent.     

禽流感病毒NP蛋白与T4噬菌体SOC蛋白的融合表达

利用PCR技术扩增禽流感病毒(avian influenza virus,AIV)NP基因。将NP基因克隆至T4噬菌体表达质粒pSOC的SOC基因(T4噬菌体表面非结构蛋白基因)下游,构建成T4噬菌体SOC位点表达NP的表达载体pSOC-NP。将其转化至大肠杆菌BL21(DE3),经IPTG诱导后表达的目的蛋白SOC-NP进行SDS-PAGE与Western-blot方法检测。结果表明,表达的SOC-NP蛋白相对分子质量约58kD,表达量占菌体总蛋白量的20.34%,并具有与AIV特异性抗体反应的活性。     

Characterization of the prfA Virulence Gene Cluster Insertion Site in Non-Hemolytic Listeria spp.: Probing the Evolution of the Listeria Virulence Gene Island

The prfA virulence gene cluster is present between prs and ldh in the pathogenic L. monocytogenes and L. ivanovii, but absent from the non-pathogenic L. innocua and L. welshimeri. To probe the evolution of this virulence gene cluster, we sequenced the prs-ldh intergenic region in L. welshimeri and L. innocua. Two ORFs (ORFA and ORFB) were found in both species as well as in L. monocytogenes. Another ORF of unknown function (ORFZ) was found in L. monocytogenes and L. innocua, while two unique ORFs were present in L. welshimeri. ORFA and ORFB showed significant functional constraint, suggesting that further investigations in the functions of these genes, including possible roles in horizontal gene transfer or sequence deletion, are warranted. DNA sequences homologous to Tn1545 integration consensus sequences were found downstream of prs and ORFB, thus defining the likely junctions of the virulence gene island and indicating that the prs-ldh intergenic region may represent a Tn insertion hot spot. Our results are consistent with the hypothesis that a combination of horizontal gene transfer and deletion events may have been involved in the evolution of the prfA virulence gene cluster in Listeria. Received: 27 November 2000 / Accepted: 20 February 2001     

Acquisition of Phage Sensitivity by Bacteria through Exchange of Phage Receptors

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