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.     

金黄色葡萄球菌附属基因调节系统研究进展

金黄色葡萄球菌的微生物病原特性非常复杂并且不断地产生抗生素抗性,目前迫切需要增加对金黄色葡萄球菌的了解。它所引起的疾病与大量毒力因子相关,这些毒力因子的表达是受多个基因调控,其中agr（accessory gene regulator,附属基因调节）是最主要的一个。由于agr系统与人类的多种疾病有关,研究的较为深入,现已成为一个理解群体感应激活和抑制机制的模型系统。agr系统以及其它菌的群体感应系统已经引起了越来越多研究者的注意,本文对agr系统的研究现状、研究过程中发现的问题及其潜在应用价值作了深入地探讨。     

群体感应与病原菌致病性研究进展

群体感应是细菌根据细胞密度变化进行基因表达调控的一种生理行为。当细菌密度达到临界阈值时能释放一些特定的自诱导信号分子,从而调节本种群或同环境中其他种群的群体行为。细菌群体感应参与包括人类、动植物、病原菌在内的多种生物的生物学功能调节,如生物膜的形成、毒力因子的产生、病原菌的耐药性等。深入研究病原菌群体感应系统的调控机制,将提高对病原菌发病机制的认识,有利于以群体感应作为防治疾病策略的研究。系统阐述了群体感应系统的组成类型、群体感应与病原菌致病性的关系,及其在抑制病原菌致病方面的应用。     

AI-2,一种新的细菌自体诱导分子

细菌通过数量阈值感应系统调节群体内个体的基因表达而使整个群体步调一致。细菌通过感应自体诱导分子(autoinducer,AI)浓度而感知周围环境中同类存在的密度,并据此调节自身特定性状的表达。AI．2是近年来新发现的一种介导细菌种间信号传导的自体诱导分子,其分子结构、功能均不同于传统的A1分子。AI．2对细菌的调节作用主要表现为对毒力基因表达的影响,但目前也有人认为AI-2可能只是一种代谢产物。     

细菌群体感应及其在病原菌防治中的应用

细菌分泌一种或多种化学信号分子,这些化学信号分子作为诱导因子感知和判断菌群密度和周围环境的变化。当菌群达到一定阈值时会启动一系列相关基因的表达以调控菌体的群体行为,细菌的这种生理行为称为群体感应。大量的研究表明,不同类型的细菌具有不同的群体感应系统。群体感应机制广泛存在于病原菌中,并与其侵染过程、毒力基因表达及致病性密切相关。利用这种群体感应机制作为靶点进行病原菌的防治是医学领域广泛关注的问题。在此就细菌群体感应及其在病原菌防治中的应用进行阐述。     

微生物群体感应系统的调控机制及应用研究进展

微生物通过群体感应监控范围内菌体数量并调节其自身相关基因的启动表达,进而完成对质粒的接合转移、毒力因子的表达、抗生素的产生和稳定期的进入等一系列相关生命活动的控制,因此群体感应对细菌群体的稳定有重要作用,随着对群体感应系统研究的深入,群体感应相关基因元件及调控原理逐渐清晰,也有许多群体感应系统被应用于实践中。本文中,笔者综述了几种当今研究比较清楚且有代表性的微生物群体感应系统及其调控元件,并且介绍了利用群体感应相关元件构建基因开关实现代谢流的动态调控,以及利用致病菌的群体感应实现微生物的检测及杀灭的应用。     

葡萄球菌呼吸相关双组分系统SrrAB研究进展

葡萄球菌呼吸相关双组分系统SrrAB能感应外界O2浓度,并将信号传至胞内,调控下游基因的转录,以应对外界环境的变化。有研究表明,金黄色葡萄球菌SrrAB在有氧条件下促进毒力因子的表达,抑制生物膜的形成;在厌氧条件下抑制毒力因子的表达,促进生物膜的形成。另外,在有氧及厌氧条件下,金黄色葡萄球菌SrrAB调控生长代谢的途径也不一致。表皮葡萄球菌中也存在类似的双组分系统SrrAB,且与金黄色葡萄球菌SrrAB具有较高同源性,但目前尚不清楚两者在生长代谢及毒力调控方面的异同。结合课题组研究工作,简要综述葡萄球菌SrrAB的调控机制,着重比较其在有氧及厌氧条件下的调控差异,这对临床诊治葡萄球菌引起的感染具有一定的借鉴意义。     

金黄色葡萄球菌非编码小RNA的研究进展

金黄色葡萄球菌(Staphylococcus aureus,S.aureus)是困扰全球公共卫生及人类健康的重要病原菌,其引起的各种临床感染与该菌表达的多种毒力因子密切相关,而这些毒力因子表达受到调节性因子的精确调控,在细菌致病机制中发挥着核心作用。非编码小RNA(Small non-coding RNA,s RNA)是基因表达的一类重要调节因子,可使细菌对环境因素做出反应,调节其应激适应性及毒力因子表达。但到目前为止,仅少数金黄色葡萄球菌s RNA的生物学功能得到阐述。本文将针对这些调节性s RNA的研究进展作一综述。     

群体感应QseB/QseC系统对外界环境变化的响应机制

细菌群体感应(quorum sensing, QS)是一种细菌种群之间和与环境之间的相互作用机制，不仅可以评估其自身物种的种群密度，还可以评估给定环境中其他细菌物种的种群密度，是维持细菌感知并响应环境变化的重要协调途径。编码鞭毛表达和组装以及运动性的基因是潜在的毒力相关因子，受细菌种群密度调节，利用群体感应激活。QseB/QseC双组分系统是参与鞭毛和运动基因调节的群体感应调节级联反应的一个重要组成部分。本文综述了细菌群体感应系统的种类及其作用，将近年来有关QseB/QseC双组分系统介导的群体感应系统结构功能、QseB/QseC信号转导调控机制以及QseB/QseC双组分系统在调控细菌致病性、生物膜形成、鞭毛运动性等方面所发挥的作用进行整理、归纳和总结，并对目前研究不足的地方作出了展望，希望能找出下一个研究的方向。对QseB/QseC信号系统介导的群体感应机制的深入研究，不仅为解决细菌耐药及致病机制等问题提供新思路，还可能为开发疫苗和药物提供新靶点。     

肠杆菌科细菌群体感应系统的研究进展

细菌能够感受种群密度的变化,并通过调节自身某些基因的表达来作出应答,这种细菌种间和种内的沟通方式被称为群体感应(QS)。肠杆菌科细菌大多是食源性致病菌或食品腐败菌,且研究证明毒力因子的调控表达和食品的腐败变质均与QS密切相关。本文中,笔者综述了肠杆菌科成员中5种信号分子介导的群体感应系统,包括N-酰基高丝氨酸内酯(AHLs)介导的Ⅰ型QS系统、由自诱导物2(AI-2)介导的Ⅱ型QS系统、AI-3/肾上腺素/去甲肾上腺素介导的Ⅲ型QS系统、一种线型五肽(NNWNN) QS因子EDF(extracellular death factor)短肽介导的QS系统和吲哚介导的QS系统,并对其在毒力基因和食品腐败变质的调控机制中的研究进行了介绍。     

GeneChip expression analysis of the VqsR regulon of Pseudomonas aeruginosa TB

Two interlinked quorum sensing circuits, las and rhl, which control pathogenesis of Pseudomonas aeruginosa are further modulated by numerous regulators, including VqsR (virulence and quorum sensing regulator). High-density oligonucleotide microarrays were used to compare the global expression profile of a wild-type and VqsR mutant in ABC minimal medium. The expression of a large group of metabolic genes, ECF sigma factors as well as of many quorum-sensing genes previously not assigned to VqsR-regulon was found to be affected by the disruption of vqsR.     

黄河鲤水产细菌的分离及其毒力因子和群体感应信号分子的检测

【背景】水产细菌病害制约水产养殖业健康发展,群体感应与细菌毒力因子的产生密切相关,群体感应调控细菌的毒力因子特性值得进一步研究。【目的】探究群体感应与黄河鲤细菌病害的关系,明确群体感应对细菌毒力因子特性的影响。【方法】通过16S rRNA基因测序并构建系统进化树确定筛选菌株的进化地位,通过脱脂牛奶平板法和偶氮酪蛋白法检测菌株胞外蛋白酶活力,采用结晶紫染色法对菌株的生物膜形成能力进行测定,通过报告菌株BB170和CV026分别测定菌株产信号分子AI-2和高丝氨酸内酯的能力,外源添加高丝氨酸内酯检测信号分子对菌株胞外蛋白酶活力和生物膜形成能力的影响。【结果】哈夫尼亚菌(Hafnia sp.) Z11和气单胞菌(Aeromonas sp.) Z12具有高水平的胞外蛋白酶活力和生物膜形成能力,能够分泌AHLs信号分子且具有菌体密度依赖性。外源添加HSL对菌株毒力因子特性有不同程度的影响,外源添加高浓度的N-丁酰基高丝氨酸内酯(C4-HSL)和N-己酰基高丝氨酸内酯(C6-HSL)能够分别提高菌株Z11和Z12的胞外蛋白酶活力和生物膜形成能力。【结论】高浓度群体感应信号分子AHLs对哈夫尼亚菌和气单胞菌胞外蛋白酶活性有促进作用,说明该2种菌的群体感应现象可能会影响其毒力。     

细菌的群体感应及与病原菌致病性的关系

微生物的群体感应(quorum sensing,QS)也称为自诱导,是微生物间通过小分子分泌物(自诱导物)在细胞与细胞之间扩散以感知群体密度,并通过自诱导物的浓度及其与转录因子的相互作用调控整个群体细胞中一系列目标基因表达的一种自我感知系统.不同的细菌类型,其QS系统也有一定的差异.根据信号分子的不同,一般可以将细菌的QS系统分为3类,即以AHL为信号分子的革兰氏阴性细菌、以寡肽类物质为信号分子的革兰氏阳性细菌和以哈氏弧菌为代表的兼具上述两种类型QS系统特征的第三类QS系统.综述革兰氏阴性细菌、革兰氏阳性细菌和哈氏弧菌的3种不同QS系统及其在病原菌致病性方面的研究进展.     

Bacterial Hypoxic Responses Revealed as Critical Determinants of the Host-Pathogen Outcome by TnSeq Analysis of Staphylococcus aureus Invasive Infection

Staphylococcus aureus is capable of infecting nearly every organ in the human body. In order to infiltrate and thrive in such diverse host tissues, staphylococci must possess remarkable flexibility in both metabolic and virulence programs. To investigate the genetic requirements for bacterial survival during invasive infection, we performed a transposon sequencing (TnSeq) analysis of S. aureus during experimental osteomyelitis. TnSeq identified 65 genes essential for staphylococcal survival in infected bone and an additional 148 mutants with compromised fitness in vivo. Among the loci essential for in vivo survival was SrrAB, a staphylococcal two-component system previously reported to coordinate hypoxic and nitrosative stress responses in vitro. Healthy bone is intrinsically hypoxic, and intravital oxygen monitoring revealed further decreases in skeletal oxygen concentrations upon S. aureus infection. The fitness of an srrAB mutant during osteomyelitis was significantly increased by depletion of neutrophils, suggesting that neutrophils impose hypoxic and/or nitrosative stresses on invading bacteria. To more globally evaluate staphylococcal responses to changing oxygenation, we examined quorum sensing and virulence factor production in staphylococci grown under aerobic or hypoxic conditions. Hypoxic growth resulted in a profound increase in quorum sensing-dependent toxin production, and a concomitant increase in cytotoxicity toward mammalian cells. Moreover, aerobic growth limited quorum sensing and cytotoxicity in an SrrAB-dependent manner, suggesting a mechanism by which S. aureus modulates quorum sensing and toxin production in response to environmental oxygenation. Collectively, our results demonstrate that bacterial hypoxic responses are key determinants of the staphylococcal-host interaction.     

Does Pseudomonas aeruginosa use intercellular signalling to build biofilm communities?

Pseudomonas aeruginosa is a Gram-negative bacterial species that causes several opportunistic human infections. This organism is also found in the environment, where it is renowned (like other Pseudomonads) for its ability to use a wide variety of compounds as carbon and energy sources. It is a model species for studying group-related behaviour in bacteria. Two types of group behaviour it engages in are intercellular signalling, or quorum sensing, and the formation of surface-associated communities called biofilms. Both quorum sensing and biofilm formation are important in the pathogenesis of P. aeruginosa infections. Quorum sensing regulates the expression of several secreted virulence factors and quorum sensing mutant strains are attenuated for virulence in animal models. Biofilms have been implicated in chronic infections. Two examples are the chronic lung infections afflicting people suffering from cystic fibrosis and colonization of indwelling medical devices. This review will discuss quorum sensing and biofilm formation and studies that link these two processes.     

MexEF-OprN efflux pump exports the Pseudomonas quinolone signal (PQS) precursor HHQ (4-hydroxy-2-heptylquinoline)

Bacterial cells have evolved the capacity to communicate between each other via small diffusible chemical signals termed autoinducers. Pseudomonas aeruginosa is an opportunistic pathogen involved, among others, in cystic fibrosis complications. Virulence of P. aeruginosa relies on its ability to produce a number of autoinducers, including 4-hydroxy-2-alkylquinolines (HAQ). In a cell density-dependent manner, accumulated signals induce the expression of multiple targets, especially virulence factors. This phenomenon, called quorum sensing, promotes bacterial capacity to cause disease. Furthermore, P. aeruginosa possesses many multidrug efflux pumps conferring adaptive resistance to antibiotics. Activity of some of these efflux pumps also influences quorum sensing. The present study demonstrates that the MexEF-OprN efflux pump modulates quorum sensing through secretion of a signalling molecule belonging to the HAQ family. Moreover, activation of MexEF-OprN reduces virulence factor expression and swarming motility. Since MexEF-OprN can be activated in infected hosts even in the absence of antibiotic selective pressure, it could promote establishment of chronic infections in the lungs of people suffering from cystic fibrosis, thus diminishing the immune response to virulence factors. Therapeutic drugs that affect multidrug efflux pumps and HAQ-mediated quorum sensing would be valuable tools to shut down bacterial virulence.     

The impact of mutations in the quorum sensing systems of Aeromonas hydrophila, Vibrio anguillarum and Vibrio harveyi on their virulence towards gnotobiotically cultured Artemia franciscana

Disruption of quorum sensing, bacterial cell-to-cell communication by means of small signal molecules, has been suggested as a new anti-infective strategy for aquaculture. However, data about the impact of quorum sensing on the virulence of aquatic pathogens are scarce. In this study, a model system using gnotobiotically cultured Artemia franciscana was developed in order to determine the impact of mutations in the quorum sensing systems of Aeromonas hydrophila, Vibrio anguillarum and V. harveyi on their virulence. Mutations in the autoinducer 2 (AI-2) synthase gene luxS, the AI-2 receptor gene luxP or the response regulator gene luxO of the dual channel quorum sensing system of V. harveyi abolished virulence of the strain towards Artemia. Moreover, the addition of an exogenous source of AI-2 could restore the virulence of an AI-2 non-producing mutant. In contrast, none of the mutations in either the acylated homoserine lactone (AHL)-mediated component of the V. harveyi system or the quorum sensing systems of Ae. hydrophila and V. anguillarum had an impact on virulence of these bacteria towards Artemia. Our results indicate that disruption of quorum sensing could be a good alternative strategy to combat infections caused by V. harveyi.