趋磁细菌WD-1的超微结构及批量培养方法*

报道了趋磁细菌WD 1的超微结构 ,菌株WD 1的超薄切片清楚地显示了细胞壁 (CW )、细胞膜 (CM)、细胞内部的聚-β-羟基丁酸 (poly β hydroxybutyrate)和磁小体 (MagnetosomesMS)。建立了菌体和磁小体批量培养和收集的方法 ,经培养每升培养基可获得 1 35mg干菌体。经SEM能谱分析菌体和磁小都含有Fe、Al、Si、P、S、Ca、Zn等元素成分 ;菌体和磁小体中铁的含量分别为 3.07%和84.57%。     

趋磁螺菌中磁小体链装配相关基因及其功能

趋磁细菌(MTB)依赖于体内磁小体结构在磁场中取向,多个磁小体以一定的组 织形式排列是形成菌体内生物磁罗盘的重要环节．多数趋磁细菌中磁小体成链排列,有效增加了细胞磁偶极矩,从而使菌体表现出在环境磁场中定向的能力．趋磁螺菌M. magneticum AMB－1和M. gryphiswaldense MSR－1中磁小体均沿细胞长轴形成一条磁 小体链．通过对相关基因突变体表型的研究,结合对磁小体链形成过程的实时动态观 察,人们已初步了解MamJ、MamK和MamA等基因在磁小体链装配和维护过程中的功能．本文介绍了近年来趋磁螺菌磁小体链装配过程中重要功能性基因的研究进展,并重点分析了AMB-1和MSR-1中磁小体链装配的差异．     

趋磁细菌的磁小体

趋磁细菌是一类对磁场有趋向性反应的细菌,其菌体能吸收外界环境中铁元素并在体内合成包裹有膜的纳米磁性颗粒Fe₃O₄或Fe₃O_{3S4晶体即磁小体。综述了趋磁细菌的磁小体生物矿化的条件,以及趋磁细菌的铁离子吸收、磁小体囊泡的形成、铁离子的转运到磁小体囊泡及囊泡中受控的Fe3O4生物矿化的分子生物学和生物化学等方面的研究进展,重点介绍了趋磁细菌磁小体合成机制的研究进展及未来研究磁小体的发展方向。}     

趋磁细菌磁小体研究进展

趋磁细菌能在细胞内形成由膜包裹的纳米级单畴磁性颗粒——磁小体。磁小体的形成是受生物严格控制的矿化过程,包括铁离子的吸收、转运和结晶成核等。磁小体膜在磁铁矿（Fe3O4）晶体的形成中起着重要的作用。主要介绍近年来关于磁小体形成过程和参与这一过程的蛋白质等方面的一些重要研究进展。     

趋磁细菌概述及应用进展

趋磁细菌是一类具有趋磁行为的革兰氏阴性茵的统称,其趋磁特性是由于菌体内含有磁小体。磁小体是由膜包被的纳米尺寸单磁畴颗粒,在菌体内多呈链状排列。自被发现以来,趋磁细菌及磁小体已逐步成为新的生物资源被广泛研究于材料学、医学、生物学、物理学、地质学等多个学科领域,并在仿生学、生态学、医学、地质学、工业处理、卫生检验等多个领域得到应用。主要介绍了趋磁细菌的生物特征、研究发展进程,以及近年来在多个学科领域的研究与应用。     

大肠杆菌RNA聚合酶σ亚基基因的表达及表达产物的分离纯化

将2种表达质拉pEGMD（含rpoD基因）和pETF（含rpoS基因）转化到BL21（DE3）菌株中,培养菌体。破碎细胞,用盐酸抓溶解包含体,经DEAE－纤维素柱层析,SDS－PAGE检测可得纯化σ的蛋白。通过紫外分光光度法测定蛋白浓度,实验表明σ38蛋白的得率为菌体温重的0．27％,σ70蛋白的得率为菌体湿重的0．06％。     

矿物作用下A.ferrooxidans中磁小体相关基因的差异表达

目的:研究氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans,A.f)中与磁小体形成相关的mpsA、magA、thy和mamB基因分别在黄铁矿、黄铜矿、磁黄铁矿和闪锌矿的作用下的表达差异,寻找有利于磁小体形成的最佳培养矿物能源。方法:测量以不同硫化矿为能源时的菌体生长特性,用实时定量PCR方法研究与磁小体形成相关基因的表达差异。结果:在以磁黄铁矿为能源时,菌的生长量及多数基因的表达量优于其它三种矿,四个基因相对表达量分别为1.15、2.35、1.32、2.68。结论:磁黄铁矿是A.f中磁小体形成的最佳矿物能源。     

趋磁细菌AMB-1生物矿化相关蛋白Mms6参与磁小体的合成

【目的】研究趋磁细菌AMB-1生物矿化相关蛋白Mms6与磁小体合成的关系。【方法】在液体静置培养条件和好氧条件下对AMB-1进行培养,分析基因mms6在不同培养条件下转录水平的变化;对基因mms6进行基因敲除,分析突变株的生长和产磁变化。【结果】基因mms6的转录水平随着磁小体的合成逐渐升高;mms6的突变导致菌株在液体静置培养条件下趋磁性降低约50%,但不会影响菌株的生长水平。【结论】基因mms6参与了趋磁细菌AMB-1胞内磁小体的合成。     

趋磁细菌及磁小体研究的回顾和展望

趋磁细菌及磁小体研究的回顾和展望陈明杰,卫扬保（武汉大学生命科学学院微生物学与免疫学系．武汉４３００７２）一趋磁细菌研究现状１趋磁细菌的发现１９７５年,美国人Ｂｌａｋｅｍｏｒｅ在显微镜下观察湖泊底部污泥的富集样品时,发现有一类细菌总是聚集在视野的靠北...     

（S）-（-）-β-羟基苯丙酸乙酯的微生物法合成

采用酿酒酵母CGMCC No．2266菌体,不对称还原β-羰基苯丙酸乙酯制备光学纯（S）-（-）-β-羟基苯丙酸乙酯。结果表明：采用初始pH为8．0的液体发酵培养基培养的CGMCCNo．2266菌体经过50℃预热处理30min后用于生物转化获得的（S）-（-）-G-羟基苯丙酸乙酯对映体过剩值可以达到100％ee。确定了合成（S）-（-）-β-羟基苯丙酸乙酯的较佳转化条件为pH7．0,温度30℃,转化时间24h,底物浓度为3．63mmol／L,菌体用量为86g/L（干重／反应体积）。以10％葡萄糖为辅助底物,产率比不加辅助底物时提高了75．4％。在最佳转化条件下反应转化率及（S）-（-）-β-羟基苯丙酸乙酯对映体过剩值可分别达到98．4％和100％ee。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.