铜绿假单胞菌群体感应系统的研究进展

细菌的群体感应也称自身诱导,是指细菌通过产生和感应信号分子浓度的变化来监测其群体密度,协调群体行为的过程.自身诱导物随着细菌密度增高而增高,当自身诱导物达到某一阈值后,会与一些转录调节子结合,从而诱导或抑制多种基因的表达.群体感应系统内由多种信号分子和效应蛋白组成复杂的调节网络,调控包括细菌毒力因子产生与释放、生物膜形成、接合反应等,从而影响细菌的致病过程.本文主要对铜绿假单胞菌的群体感应系统及其与宿主关系、群体感应抑制剂等方面的研究进展进行综述.     

铜绿假单胞菌群体感应系统研究进展

群体感应系统是一种细胞密度依赖的基因表达系统,其广泛存在于细菌性病原体中,是细菌细胞通讯方式的一种。群体感应系统可利用细菌释放的信号分子不断监控周围细菌的密度。当细菌密度达到阈值时,群体感应系统网络将启动,参与调控生物被膜、细菌毒力等特定基因的表达,从而使临床抗感染治疗失败。而通过抑制群体感应系统,可一定程度上治疗铜绿假单胞菌引起的感染。本文通过查阅近年国内外相关文献,对铜绿假单胞菌群体感应系统研究进展进行总结,为临床铜绿假单胞菌治疗提供新的方向,即群体感应系统抑制剂有可能成为治疗铜绿假单胞菌感染的新策略。     

粘质沙雷氏菌AS-1中SpnR功能及卤化呋喃对其群体感应的抑制

通过分泌和感知一系列信号分子,细菌能够根据自身菌体密度的变化调控基因的表达,从而控制一系列重要的表现型,包括毒力因子的产生,生物膜的形成以及菌体发光等.这种广泛存在的信号机制被称为群体感应.在沙雷氏菌种中已经发现了多套群体感应机制.粘质沙雷氏菌AS-1从土壤中分离,其中含有LuxI/LuxR的同类蛋白,被称为SpnI/SpnR.粘质沙雷氏菌AS-1合成AHLs分子N-hexanoy1-L-homoserinelactone(C6-HSL)和N-(3.oxohexanoyl)-L-homoserine lactone(3-oxo-C6-HSL)作为其信号分子,通过群体感应感知菌体密度来控制基因的表达.通过基因替代的方法制得了spnR基因破坏的变异株,命名为粘质沙雷氏菌AS-1R.对粘质沙雷氏菌AS-1R的研究表明SpnR蛋白消极的调控沙雷氏菌红色色素的产生,运动性以及生物膜的形成等一系列由群体感应控制的性状:另一方面,作为一种天然的群体感应抑制剂,卤化呋喃能够有效的抑制粘质沙雷氏菌AS-1的群体感应,但并不干扰AHL-SpnR的相互作用.为运用粘质沙雷氏菌群体感应调节抑制其致病性提供了方法和依据,同时也为卤化呋喃对群体感应抑制机理的研究提供了新的思路.     

真菌群体感应现象的研究进展

群体感应是细菌中普遍存在的细胞与细胞间的通讯系统,即细菌可通过向环境释放可扩散的信号分子来感知细胞群体密度并调控自身的某些生理行为。近年来研究发现,真菌中也存在类似于细菌群体感应信号分子的信息素,并参与调节真菌诸如菌相转化、致病性及次级代谢产物产生等生理行为。主要综述了目前真菌中群体感应系统的研究进展。     

细菌群体感应的信号转导机制及其对抗生素生产的影响

摘要：细菌的群体感应是一种群体行为调控机制。自然界中的很多细菌都有这种能力,即分泌一种或多种信号分子,通过这些信号分子的浓度来感知菌群密度,调控一系列相应靶基因的表达。在这些受调控的基因中,备受关注的是信号分子对抗生素生产的调节。本文综述了群体感应机制的最新研究进展和它对抗生素生产的调节,尤其对洋葱伯克霍尔德菌(Burkholderia. cepacia)进行了较为详细的探讨。     

在DH5α中拼接构建ADAM10全长真核表达载体的基因突变

目的:构建ADAMI0真核表达载体,为进一步研究其生物学功能打基础.方法:将人ADAM10的上下两部分基因片段(分别为全长基因的1 ～910bp和911 ～2 247bp片段),依次与真核表达载体pcDNA3.1相连,以大肠杆菌DH5α或BL21(DB)作为感受态宿主菌用于转化连接产物,拼接成全长的阳性克隆通过PCR、酶切和测序鉴定.结果:ADAM10下段基因与已正确连入上段的pcDNA3.1重组质粒拼接时,若用DH5α为感受态菌,则下半段出现碱基插入增加512bp,测序结果显示为ADAM10基因第1 531 bp～2 042 bp间的序列有紧邻的双份;若用BL21(DE3)为感受态,则无突变.结论:将ADAM10基因与pcDNA3.1真核表达载体依次拼接构建重组质粒时,以DH5α为宿主菌可出现基因序列增加的罕见突变,而以BL21(DE3)为宿主则无突变,由此成功构建ADAM10全长基因与pcDNA3.1的重组质粒.     

透明颤菌血红蛋白的DNA改组研究

为提高透明颤菌血红蛋白在限氧条件下促进宿主细胞生长的能力,首先通过易错PCR向透明颤菌血红蛋白基因中引入突变,再结合DNA改组对其进行改造。将改组基因置于透明颤菌血红蛋白天然启动子下游,转化大肠杆菌DH5α,构建改组文库。以限氧培养条件下菌体沉淀的颜色为指标进行试管初筛,再以限氧和极端限氧条件下菌体湿重为指标进行摇瓶复筛,最终得到一个高活性突变蛋白VHb'042506。该蛋白使宿主的菌体湿重在限氧和极端限氧条件下较原基因转化子分别提高了31.25%和58.75%。经测序和比对,该基因与原基因相比发生了11处碱基点突变,致氨基酸4处错义突变。CO差光谱实验显示该蛋白具有更强的特征吸收。     

副溶血性弧菌群体感应蛋白CqsA的原核表达

副溶血性孤菌CqsA是一种推测的信号分子合成酶,其合成的信号分子在群体感应系统中可能具有重要的调控作用.从副溶血性弧菌ATCC 17802中克隆cqsA基因,构建重组质粒pET22b-cqsA.测序后转化大肠杆菌B1L21进行IPTG诱导表达,使用SDS-PAGE分析融合蛋白的表达状况,并通过6× His-Tag进行Western blotting检测.结果显示,经0.6 mmol/L IPTG诱导4h,目的基因以包涵体形式高效表达,表达的融合蛋白大小约为49 kD,与理论值相符(437 aa).表明副溶血性弧菌群体感应蛋白CqsA在大肠杆菌中成功表达,为后续寻找副溶血性孤菌群体感应信号分子,进一步探索副溶血性弧菌群体感应系统提供参考.     

群体感应及其在动物病原菌致病中的作用

摘要: 群体感应是指微生物群体某些基因的表达受到与群体密度相关的信号分子调控的现象。微生物以酰基高丝氨酸内酯化合物,某些短肽分子,呋喃酮类化合物,以及一些小分子物质为信号分子,介导不同的群体感应系统。各群体感应系统之间以平行协同或层次串连的方式组织起来调控微生物各种基因。众多病原菌致病基因的表达与群体感应密切相关,主要表现在：群体感应帮助微生物对宿主的侵袭和定殖;调控毒力因子的产生和作用于宿主;以及介导病原菌对宿主的免疫能力和药物抗性。进行群体感应对微生物致病过程调控的研究,将有利于从群体感应入手进行病原菌防控新策略的探索。     

密度感应系统对弗氏志贺菌生长竞争能力的影响

密度感应系统调节细菌应答反应的发生,这些应答反应与细胞密度有关。通过对比大肠杆菌(Escherichia coli)和志贺氏菌(Shigella spp.)的序列发现,志贺菌属密度感应系统操纵子普遍存在丢失或突变。为研究其密度感应系统的功能,文章利用哈氏弧菌(Vibrio harveyi)BB170作为指示菌,检测弗氏志贺菌(Shigella flexneri)密度感应系统信号分子AI-2,证明其可以分泌有活性的AI-2;其次,采用Golden Gate克隆法将大肠杆菌MG1655的密度感应系统基因克隆至弗氏志贺菌301中,获得密度感应系统回复株301。通过菌落计数表明,在混合培养条件下,密度感应系统基因回复株301比野生株301存在生长优势;通过双向电泳初步比较分析表明,密度感应系统基因可以在志贺菌中表达,并鉴定到了其他一些与应激反应相关的差异表达蛋白, 如Hsp60、GroEL、SodB。     

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.