细菌群体感应信号分子——酰基高丝氨酸内酯的检测

革兰氏阴性菌根据信号分子N-酰基高丝氨酸内酯(AHLs)的浓度可以监测周围环境中自身或其他细菌的数量变化,当信号分子达到一定浓度阈值时,能启动相关基因的表达来适应环境的变化,这一调控系统被称为细菌的群体感应(quorumsensing,QS)系统。快速简便而有效地检测细菌是否以及产生何种信号分子成为深入研究和了解细菌群体感应的重要手段。现对信号分子AHLs敏感的用于检测不同的信号分子AHLs的微生物传感菌进行综述,并对其检测能力进行了讨论。     

信息素——细菌相互交流的物质基础

信息素是细菌分泌到体外的一些物质,这些物质能被同种菌的其它个体所接受,并引起它们产生某一种特殊反应,比如一个特定的行为或生长过程,微小的量就能起作用［’］。信息素有M＄基一L－一高丝氨酸内酯（N-acyl-L-homoserinelactones,即AHLs）、丁酸内酯、氨基酸、肽链、低分子量的脂类等多种类型,本文将重点讨论AHLs信息素系统。1AHLs调控系统AHLs首先是在发光细菌中发现的,目前在许多革兰氏阴性菌中均有报道。AHLs由LuxI族蛋白诱导产生,然后通过细胞膜扩散至胞外,并在培养基中积累。如果AHLs在细胞外积累到一定的浓度,…     

细菌群体感应LuxR solos蛋白研究进展

N-酰基高丝氨酸内酯(N-acyl-L-homoserine lactones,AHLs)信号分子介导的群体感应(quorum sensing,QS)是一种普遍的革兰氏阴性细菌信息交流方式。AHL-QS系统包括Lux I型AHLs合成酶和LuxR型受体蛋白。然而,部分革兰氏阴性菌缺失1个或多个LuxI型AHLs合成酶,仅有未配对的LuxR型受体蛋白,该LuxR型受体蛋白称为LuxR solo或Orphan蛋白。LuxR solos蛋白在细菌窃听、种间和种内的信号交流中起重要作用,为群体感应研究领域的热点。本文主要综述细菌LuxR solos蛋白的发现、基本概念、蛋白结构及类型,阐述感应AHLs和非AHLs信号分子的重要LuxR solos蛋白及功能,并对群体感应LuxR solos蛋白的研究前景和意义进行了展望。     

群体感应信号分子及其抑制剂快速检测方法的建立

细菌能自发产生、释放一些特定的信号分子,并能感知其浓度变化,调节微生物的群体行为,这一调控系统称为群体感应。细菌群体感应参与包括人类、动植物病原菌致病力在内的多种生物学功能的调节,群体感应抑制剂成为抗感染药物开发的靶点。利用紫色色杆菌(Chromobacterium violaceum)和根癌农杆菌(Agrobacterium tumefaciens)作为指示菌,建立检测高丝氨酸内酯(AHLs)及其抑制剂的简便方法。结果表明,通过平板交叉划线接种,使用指示菌能够有效地检测AHLs,并且通过薄层层析(TLC)与细菌生物感应器相结合的方法可以快速、方便地鉴定AHLs的种类;通过双层平板法观察指示菌色素产生情况,能够有效地检测群体感应信号分子AHLs抑制剂,且该方法简单易行。     

内生菌Pseudomonas sp. G5 phzIR基因的克隆与表达

假单胞菌菌株G5是分离自香菜(Coriandrum sativumL.)茎内的一株内生菌,经BIOLOG系统分析其底物利用图谱,初步鉴定为桔黄假单胞菌Pseudomonas aurantiaca。大量研究已表明许多革兰氏阴性细菌应用群体感应系统,通过感应扩散性小信号分子―乙酰基高丝氨酸内酯(N-acyl homoserine lactones,AHLs),以种群密度依赖的方式调控基因表达,控制植物相关细菌的多种表型。本研究组合应用AHLs检测菌株Chromobacterium violaceum CV026和薄层层析分析,初步检测出菌株G5可产生几种可检测水平的AHLs信号分子,其中以N-hexanoyl-homoserine lactone(C6-HSL,HHL)为主,迁移率Rf值为0.4。进一步克隆和测序了该菌株中由PhzI和PhzR组成的群体感应quorumsensing系统的编码基因phzIR,并在大肠杆菌中异源表达了AHLs信号分子合成酶基因phzI。序列和系统进化分析表明它们与假单胞菌属其他的phzIR基因有高度同源性和进化上的保守性。     

细菌毒力的环境调控——在疫苗研制生产中的应用

<正>菌苗研制的主要根据是细菌体外培养时所表现出的抗原性结果。它只能部分显示细菌与毒力、细菌与保护性免疫应答之间的关系,而不能真正反映病原菌在宿主体内环境的全部表现。因此,由宿主环境调控表达的抗原,以及与调控有关的感觉信号,目前更为引人注目。     

铁和细菌

在传染过程中铁元素起着非常重要的作用。宿主组织的内环境对其中病原菌的特性和生长的影响都与病原菌对铁的利用有关。传染过程得以发生的基本因素是病原菌侵袭力,即在宿主体内各种环境条件下病原菌成功繁殖的能力。病原性微生物必须摄取足够的铁方能在宿主体内生长繁殖,而宿主组织中可供细菌所利用的铁有时是有限的。此外,环境中铁的存在与否也是协调细菌毒力     

细菌中群体感应调节系统

细菌根据特定信号分子的浓度可以监测周围环境中自身或其它细菌的数量变化,当信号达到一定的浓度阈值时,能启动菌体中相关基因的表达来适应环境中的变化,这一调控系统被称为细菌的群体感应调节系统(QuorumSensing系统)。本文系统介绍了细菌感知种内与种间数量的群体感应调节系统,并阐述了植物针对病原菌这一信号系统的抗病策略。     

3-羰基辛酰基高丝氨酸内酯诱导拟南芥根细胞Ca~（2＋）内流

N-酰基高丝氨酸内酯（AHLs）是革兰氏阴性细菌群体感应系统（QS）中的胞间通讯信号分子。近年的研究表明AHLs可以调控植物生长发育及防卫反应,但其调控机制尚不清楚。本研究以拟南芥为材料,采用3-羰基辛酰基高丝氨酸内酯（3OC8-HSL）处理转水母发光蛋白基因的拟南芥幼根细胞,利用冷光仪检测3OC8-HSL对拟南芥根细胞中胞质游离Ca2＋浓度（[Ca2＋]cyt）变化的影响,同时采用Ca2＋专一性螯合剂EGTA和Ca2＋通道抑制剂预处理转基因拟南芥根细胞,用全细胞膜片钳技术分析3OC8-HSL诱导拟南芥根细胞中[Ca2＋]cyt升高的Ca2＋来源。结果表明,3OC8-HSL可诱导拟南芥根细胞中[Ca2＋]cyt瞬时升高。这种诱导效应可被EGTA、异搏定（verapamil）、LaCl3所抑制,但LiCl预处理对这种诱导效应无影响。膜片钳分析结果显示,3OC8-HSL可激活质膜Ca2＋通道,增加胞外Ca2＋内流。说明细菌AHLs可诱导植物Ca2＋信号产生,且这种Ca2＋信号主要源于胞外Ca2＋内流,暗示Ca2＋信使系统参与植物对细菌QS信号的响应。     

仿刺参“腐皮综合症”病灶处优势菌的分离鉴定及AHLs信号分子的检测

仿刺参"腐皮综合症"是一种由细菌引起的高传染性、高死亡率疾病.为了研究仿刺参"腐皮综合症"病灶处优势菌以及其是否存在N-酰基高丝氨酸内酯类化合物(AHLs)介导的群体感应系统,本文从患病仿刺参病灶处分离纯化出7株优势菌,生理生化指标测定和16S rDNA序列分析表明:菌株C6属Tenacibaculum属,菌株4属于腐败希瓦菌群(Shewanella putrefaciens group),菌株TB属于弧菌属(Vibrio),菌株BP2、BP3、BP4及BP6属于假交替单胞菌属(Pseudoalteromonas).采用AHLs的高效检测菌株根癌农杆菌(Agrobacterium tumefaciens KYC55)对优势菌的AHLs活性进行检测,其中菌株C6、4、TB、BP3及BP4存在以AHLs为信号分子的群体感应系统,菌株BP2与BP6则无AHLs活性;不同细菌AHLs活性不同,AHLs活性从高到低顺序为4＞TB＞BP4＞BP3＞C6.     

The plant pathogen Erwinia amylovora produces acyl-homoserine lactone signal molecules in vitro and in planta

We report for the first time the production of acyl homoserine lactones (AHLs) by Erwina amylovora, an important quarantine bacterial pathogen that causes fire blight in plants. E. amylovora produces one N-acyl homoserine lactone [a N-(3-oxo-hexanoyl)-homoserine lactone or a N-(3-hydroxy-hexanoyl)-homoserine lactone] quorum sensing signal molecule both in vitro and in planta (pear plant). Given the involvement of AHLs in plant pathogenesis, we speculate that AHL-dependent quorum sensing could play an important role in the regulation of E. amylovora virulence.     

Evidence for acyl homoserine lactone signal production in bacteria associated with marine sponges

We report for the first time the production of acyl homoserine lactones (AHLs) by bacteria associated with marine sponges. Given the involvement of AHLs in bacterial colonization of many higher organisms, we speculate that such quorum sensing signals could play a part in interactions between sponges and the dense bacterial communities living within them.     

Evidence for Acyl Homoserine Lactone Signal Production in Bacteria Associated with Marine Sponges

We report for the first time the production of acyl homoserine lactones (AHLs) by bacteria associated with marine sponges. Given the involvement of AHLs in bacterial colonization of many higher organisms, we speculate that such quorum sensing signals could play a part in interactions between sponges and the dense bacterial communities living within them.     

N-酰基高丝氨酸内酯调控植物生长发育的研究进展

植物与细菌之间存在着复杂的相互作用关系。N-酰基高丝氨酸内酯（AHLs）是革兰氏阴性细菌进行胞间通讯的信号分子,也是介导植物与细菌互作的重要信号分子,在调控植物生长发育方面起着重要作用。本文对近年来的相关研究进展作一综述,这将有助于全面了解植物与细菌间的信息交流机制,并对实际农业生产具有指导意义。     

Acyl homoserine lactones from culture supernatants of Pseudomonas aeruginosa accelerate host immunomodulation

The virulence of Pseudomonas aeruginosa is multifactorial and under the control of quorum sensing signals, such as acyl homoserine lactones (AHLs). The importance of these molecules in the establishment of infection has been previously reported. These molecules either improve the virulence potential of P. aeruginosa or modulate the host immune response. To establish the immune modulating potential of quorum sensing signal molecules, previous studies have only used synthetic AHLs. However, there can be differences in the biological properties of synthetic and natural AHLs. The use of naturally extracted AHLs from the culture supernatant of P. aeruginosa is likely to simulate natural conditions more than the use of synthetic AHLs. Therefore, in the present study, the immune modulating potential of synthetic and naturally extracted AHLs was compared using a thymidine uptake assay, immunophenotyping and sandwich ELISA in order to assess mouse T-cell proliferation and production of Th1 and Th2 cytokines. Natural AHLs were able to suppress T-cell proliferation, even at low concentrations, compared to synthetic AHLs. The majority of cells undergoing proliferation were CD4+, as revealed by immunophenotyping. The inhibition of T-cells was stronger with natural AHLs compared to synthetic AHLs. Moreover, the natural AHLs were also able to shift immune responses away from host protective Th1 responses to pathogen protective Th2 responses.     

Acyl-homoserine lactones modulate the settlement rate of zoospores of the marine alga Ulva intestinalis via a novel chemokinetic mechanism

Bacteria utilize quorum sensing to regulate the expression of cell density-dependant phenotypes such as biofilm formation and virulence. Zoospores of the marine alga Ulva intestinalis exploit the acyl-homoserine lactone (AHL) quorum sensing system to identify bacterial biofilms for preferential settlement. Here, we demonstrate that AHLs act as strong chemoattractants for Ulva zoospores. Chemoattraction does not involve a chemotactic orientation towards the AHL source. Instead, it occurs through a chemokinesis in which zoospore swimming speed is rapidly decreased in the presence of AHLs. The chemoresponse to AHLs was dependant on the nature of the acyl side chain, with N-(3-oxododecanoyl)-homoserine lactone (30-C12-HSL) being the most effective signal molecule. Mean zoospore swimming speed decreased more rapidly over wild-type biofilms of the marine bacteria Vibrio anguillarum relative to biofilms of the vanM mutant, in which AHL synthesis is disrupted. These data implicate a role for AHL-mediated chemokinesis in the location and preferential settlement of Ulva zoospores on marine bacterial assemblages. Exposure to AHLs did not inhibit the negative phototaxis of Ulva zoospores, indicating that chemoattraction to bacterial biofilms does not preclude the response to a light stimulus in substrate location.     

Bacterial quorum sensing in symbiotic and pathogenic relationships with hosts*

Gram-negative bacteria communicate with each other by producing and sensing diffusible signaling molecules. This mechanism is called quorum sensing (QS) and regulates many bacterial activities from gene expression to symbiotic/pathogenic interactions with hosts. Therefore, the elucidation and control of bacterial QS systems have been attracted increasing attention over the past two decades. The most common QS signals in Gram-negative bacteria are N-acyl homoserine lactones (AHLs). There are also bacteria that employ different QS systems, for example, the plant pathogen Ralstonia solanacearum utilizes 3-hydroxy fatty acid methyl esters as its QS signals. The QS system found in the endosymbiotic bacterium associated with the fungus Mortierella alpina, the development of an affinity pull-down method for AHL synthases, and the elucidation of a unique QS circuit in R. solanacearum are discussed herein.