群体感应与微生物耐药性

微生物耐药性已成为全球关注的严重问题,其演化机制和调控机理也已成为研究热点。近年来的研究发现,一些微生物耐药性机制受到群体感应系统的调控。群体感应是一种在微生物界广泛存在并与菌体密度关联的细胞-细胞间的通讯系统。高密度的菌落群体能够产生足够数量的小分子信号,激活下游包括致病毒力和耐药性机制在内的多种细胞进程,耐受抗生素并且危害寄主。本文结合国内外最新的研究进展,对微生物群体感应系统的研究现状进行了概括性介绍,重点阐述了群体感应系统对微生物耐药性机制的调控作用,如微生物生物被膜形成和药物外排泵调控等方面的作用,并探讨了利用群体淬灭控制微生物耐药性的新策略。     

群体感应与群体淬灭及其在抗微生物感染中的潜在应用

自从发现群体感应现象以来,由于其可替代抗生素药物以避免抗药性突变株出现的潜在应用前景,有关群体感应与群体淬灭研究日益受到人们的广泛关注,相关研究的进展速度促使研究者无法不相信群体淬灭机制作为新药开发的巨大价值。我们重点讨论了群体感应与群体淬灭的作用机制,并探讨了以群体淬灭方式作为抗病原性药物开发的应用前景。     

海洋微生物群体感应与群体感应淬灭的开发利用

群体感应与感应淬灭在微生物中普遍存在,群体感应通过调控基因表达赋予细菌有益或有害的特性,这些特性与人类健康、农业及水产养殖等领域密切相关。群体感应现象首先发现于海洋环境,近几年海洋采样等相关技术的发展,极大促进了海洋微生物的群体感应与淬灭研究的快速发展。本文对细菌及典型真菌的群体感应作用机制、信号分子的多样性以及其与细菌致病性的相关性进行了阐述,对群体感应淬灭的机制与意义、淬灭因子多样性以及相关酶资源的发掘也进行了分析和展望。     

基于Lux型群体感应系统干预的生物被膜调控在污水处理中的研究进展与前景

基于Lux型群体感应系统的生物被膜调控在污水处理中的研究备受关注,群体感应系统的干预包括正向强化和负向削弱两类。群体感应系统的正向强化作用可提高生物膜法污水处理中的挂膜速度,提高污水处理效率,促进活性污泥中胞外聚合物(Extracellular polymeric substance,EPS)和可溶性微生物产物(Soluble microbial products,SMP)的生成,提高生物被膜的产量;群体感应的负向削弱作用可以降解生物被膜形成过程中所需要的信号分子,切断生物被膜形成的基因表达过程,有效抑制MBR膜表面生物被膜的形成,防止膜污染。对信号分子酰基高丝氨酸内酯(N-acyl homoserine lactone,AHLs)的结构和作用机理的进一步研究、群体感应淬灭菌的固定化技术与应用、多种防治膜污染方法的协同效果验证及群体感应干预在更多污水处理领域的应用可行性是该领域要研究的几个重要方向。     

LuxR家族调控蛋白的结构及功能

LuxR家族调控蛋白是一类在革兰氏阴性细菌群体感应中起重要作用的调控蛋白,它们参与由酰基高丝氨酸内酯介导的多种生物学过程,调控细菌生物发光、质粒转移、生物膜形成以及多种胞外酶、毒力因子和次生代谢产物的合成。LuxR家族蛋白的研究在医学、环境监测、生物防治和微生物发酵等方面具有巨大的应用潜力。该文综述了LuxR家族调控蛋白近期的研究进展、存在问题及应用前景。     

Shoot the messages not the messengers

Microbes use quorum sensing (QS) as a mechanism to regulate host colonization and virulence in the rhizosphere. Various Gram-positive and Gram-negative bacteria engage in quorum sensing as a mode of communication to inflict pathogenicity on hosts. Of late, the use of various microbial biocontrol agents to restrict pathogenic fungi and bacteria has gained some pace. Although, not much is known about direct antagonistic mechanisms adapted by various biocontrol agents on pathogens, it still represents a sustainable technique to control pathogenesis. Crépin et al. (2012) in this issue of Plant Soil address, for the first time, the question of regulating quorum sensing (QS) by quorum-quenching (QQ) techniques. Crépin et al. show that a rhizosphere bacteria Rhodococcus erythropolis catabolizes the N-acylhomoserine lactones (N-AHLs) produced by Pectobacterium atrosepticum, thus attenuating its virulence. Their experimental results strongly support the involvement of inter-bacterial communication in the rhizosphere. This knowledge is of crucial importance for putting into practice sustainable disease-protection strategies for biocontrol technologies.     

Quorum sensing inhibitors: An overview

Excessive and indiscriminate use of antibiotics to treat bacterial infections has lead to the emergence of multiple drug resistant strains. Most infectious diseases are caused by bacteria which proliferate within quorum sensing (QS) mediated biofilms. Efforts to disrupt biofilms have enabled the identification of bioactive molecules produced by prokaryotes and eukaryotes. These molecules act primarily by quenching the QS system. The phenomenon is also termed as quorum quenching (QQ). In addition, synthetic compounds have also been found to be effective in QQ. This review focuses primarily on natural and synthetic quorum sensing inhibitors (QSIs) with the potential for treating bacterial infections. It has been opined that the most versatile prokaryotes to produce QSI are likely to be those, which are generally regarded as safe. Among the eukaryotes, certain legumes and traditional medicinal plants are likely to act as QSIs. Such findings are likely to lead to efficient treatments with much lower doses of drugs especially antibiotics than required at present.     

革兰氏阴性细菌LuxR/I型群体感应抑制剂研究进展

摘要：细菌群体感应（Quorum sensing, QS）被视为对抗细菌感染与解决细菌耐药性问题的新靶点。以AHLs为信号分子的LuxR/I型群体感应系统广泛存在于革兰氏阴性菌包括多种临床致病菌中,因此寻找LuxR/I型群体感应抑制剂（Quorum sensing inhibitors, QSIs）是研发抗革兰氏阴性致病菌药物的重要途径。迄今为止,已知的LuxR/I型小分子QSIs来源包括化学合成、天然产物与已知药物库的化合物,大分子则包括群体感应淬灭酶与群体感应淬灭抗体。本文总结了近年来LuxR/I型QSIs研究进展,为新型抗菌药物研发提供理论依据。     

Bactericidal,quorum quenching and anti-biofilm nanofactories: a new niche for nanotechnologists

Despite several conventional potent antibacterial therapies, bacterial infections pose a significant threat to human health because they are emerging as the leading cause of death worldwide. Due to the development of antibiotic resistance in bacteria, there is a pressing demand to discover novel approaches for developing more effective therapies to treat multidrug-resistant bacterial strains and biofilm-associated infections. Therefore, attention has been especially devoted to a new and emerging branch of science “nanotechnology” to design non-conventional antimicrobial chemotherapies. A range of nanomaterials and nano-sized carriers for conventional antimicrobial agents have fully justified their potential to combat bacterial diseases by reducing cell viability, by attenuating quorum sensing, and by inhibiting/or eradicating biofilms. This communication summarizes emerging nano-antimicrobial therapies in treating bacterial infections, particularly using antibacterial, quorum quenching, and anti-biofilm nanomaterials as new approaches to tackle the current challenges in combating infectious diseases.     

青岛近海沉积物生物被膜中密度感应及密度感应淬灭细菌多样性

【背景】细菌密度感应(Quorum sensing,QS)是指细菌利用分泌的信号分子进行相互交流的现象,而密度感应淬灭(Quorumquenching,QQ)是指通过干扰信号分子的产生、释放、积累或应答从而阻抑密度感应通路。【目的】探究青岛近海沉积物生物被膜中密度感应和密度感应淬灭细菌的多样性。【方法】采用海水培养基2216E从青岛近海沉积物生物被膜中分离获取可培养细菌,采用平板交互划线和高通量筛选的方法分别筛选具有密度感应和密度感应淬灭的菌株。【结果】共分离获得83株共54种具有密度感应和密度感应淬灭的细菌,分属于四大细菌门类:变形菌门、拟杆菌门、厚壁菌门和放线菌门。其中,38株(45.8%)可以产生酰基高丝氨酸内酯(Acyl-homoserine lactone,AHL)类信号分子,它们分属于变形菌门(37株,15种)和拟杆菌门(1株,1种),优势属为弧菌属和鲁杰氏菌属;能够降解AHL类信号分子的有57株(68.7%),在变形菌门(41株,23种)、拟杆菌门(14株,10种)、厚壁菌门(5株,5种)以及放线菌门(1株,1种)中均有分布。【结论】在青岛近海沉积物生物被膜可培养细菌中,具有密度感应和密度感应淬灭现象的菌株具有很高的丰度和多样性,为后续生态学意义的研究与海洋微生物的开发提供了参考。     

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。     

Inhibition of Biofilm Formation by T7 Bacteriophages Producing Quorum-Quenching Enzymes

Bacterial growth in biofilms is the major cause of recalcitrant biofouling in industrial processes and of persistent infections in clinical settings. The use of bacteriophage treatment to lyse bacteria in biofilms has attracted growing interest. In particular, many natural or engineered phages produce depolymerases to degrade polysaccharides in the biofilm matrix and allow access to host bacteria. However, the phage-produced depolymerases are highly specific for only the host-derived polysaccharides and may have limited effects on natural multispecies biofilms. In this study, an engineered T7 bacteriophage was constructed to encode a lactonase enzyme with broad-range activity for quenching of quorum sensing, a form of bacterial cell-cell communication via small chemical molecules (acyl homoserine lactones [AHLs]) that is necessary for biofilm formation. Our results demonstrated that the engineered T7 phage expressed the AiiA lactonase to effectively degrade AHLs from many bacteria. Addition of the engineered T7 phage to mixed-species biofilms containing Pseudomonas aeruginosa and Escherichia coli resulted in inhibition of biofilm formation. Such quorum-quenching phages that can lyse host bacteria and express quorum-quenching enzymes to affect diverse bacteria in biofilm communities may become novel antifouling and antibiofilm agents in industrial and clinical settings.     

Microbial population dynamics and proteomics in membrane bioreactors with enzymatic quorum quenching

Quorum sensing gives rise to biofilm formation on the membrane surface, which in turn causes a loss of water permeability in membrane bioreactors (MBRs) for wastewater treatment. Enzymatic quorum quenching was reported to successfully inhibit the formation of biofilm in MBRs through the decomposition of signal molecules, N-acyl homoserine lactones (AHLs). The aim of this study was to elucidate the mechanisms of quorum quenching in more detail in terms of microbial population dynamics and proteomics. Microbial communities in MBRs with and without a quorum quenching enzyme (acylase) were analyzed using pyrosequencing and compared with each other. In the quorum quenching MBR, the rate of transmembrane pressure (TMP) rise-up was delayed substantially, and the proportion of quorum sensing bacteria with AHL-like autoinducers (such as Enterobacter, Pseudomonas, and Acinetobacter) also decreased in the entire microbial community of mature biofilm in comparison to that in the control MBR. These factors were attributed to the lower production of extracellular polymeric substances (EPS), which are known to play a key role in the formation of biofilm. Proteomic analysis using the Enterobacter cancerogenus strain ATCC 35316 demonstrates the possible depression of protein expression related to microbial attachments to solid surfaces (outer membrane protein, flagellin) and the agglomeration of microorganisms (ATP synthase beta subunit) with the enzymatic quorum quenching. It has been argued that changes in the microbial population, EPS and proteins via enzymatic quorum quenching could inhibit the formation of biofilm, resulting in less biofouling in the quorum quenching MBR.     

微生物的交流信号

多年来微生物一直被认为是相对孤立的个体,在环境中独立地生存,但近些年的研究使人们认识到微生物也使用复杂多样的方式进行种内、种间,甚至与其他生物间的跨界信息交流。这些交流由特定的信号分子来完成,称之为微生物语言。借助这些交流语言使微生物在特定的生态位中与其相邻个体或种群建立了多样的互动关系,包括合作、竞争与资源共享等,通过协调群体行为,共同应对多变的环境。随着现代分子科学对自然微生物群落的不断深入研究,人们对微生物交流也逐渐有了更为清晰的认知。本综述总结了原核和真核微生物所使用的主要信号物质(如群体感应、群体猝灭、抗生素等)和交流方式,讨论了这些通讯语言在种内(同种微生物)、种间(异种微生物),以及跨界(微生物与宿主)交流上的表现。旨在更为深入地解读这一有趣的多学科交叉研究领域,更好地理解微生物交流语言的形式、机制和目的,为微生物行为的解读和生态事件的解析获取基于化学生态学的新思路。     

RND家族外排泵及其与微生物群体感应系统的相互关系

抗生素耐药性一直是细菌病害防治的难题,药物外排泵过量表达是细菌耐药性形成的重要机制之一。在革兰氏阴性细菌中,RND(Resistance-nodulation-cell division)家族外排泵在耐药性中发挥着重要作用,近年来的研究表明,依赖于小分子信号物质进行调控的群体感应系统与RND外排泵家族之间存在紧密的相互作用关系。本文在介绍RND家族外排泵的结构、转运机理和群体感应系统的类型及调控方式的基础上,剖析了群体感应系统对RND外排泵的调控机理以及RND外排泵对群体感应系统信号分子转运的影响。深入研究RND家族外排泵与群体感应系统之间的相互依赖、相互制约关系有利于阐明RND家族外排泵的调控机理,并有可能为克服微生物耐药性问题提供新的思路。     

Quorum quenching activity in Anabaena sp. PCC 7120: identification of AiiC, a novel AHL-acylase

Many bacteria use quorum sensing (QS) to coordinate responses to environmental changes. In Gram-negative bacteria, the most extensively studied QS systems rely on the use of N -acylhomoserine lactones (AHLs) signal molecules. Some bacteria produce enzymes that are able to inactivate AHL signals produced by other bacteria and hence interfere with QS-mediated processes via a phenomenon known as quorum quenching. Acylase-type AHL degradation activity has been found in the biomass of the filamentous nitrogen-fixing cyanobacterium Anabaena ( Nostoc ) sp. PCC 7120, being absent from the culture media. The gene all3924 has been identified and cloned whose product exhibits homology to the acylase QuiP of Pseudomonas aeruginosa PAO1, demonstrating that it is at least partially responsible for the AHL-acylase activity. The recombinant enzyme, which was named auto-inducer inhibitor from Cyanobacteria (AiiC), shows broad acyl-chain length specificity. Because the presence of AHLs in the biomass of nitrogen-fixing cultures of Anabaena sp. PCC 7120 has been described recently, AiiC could represent a self-modulatory system to control the response to its own QS signals but could also be involved in the interference of signalling within complex microbial communities in which Cyanobacteria are present.     

Monitoring of Vibrio harveyi quorum sensing activity in real time during infection of brine shrimp larvae

Quorum sensing, bacterial cell-to-cell communication, has been linked to the virulence of pathogenic bacteria. Indeed, in vitro experiments have shown that many bacterial pathogens regulate the expression of virulence genes by this cell-to-cell communication process. Moreover, signal molecules have been detected in samples retrieved from infected hosts and quorum sensing disruption has been reported to result in reduced virulence in different host–pathogen systems. However, data on in vivo quorum sensing activity of pathogens during infection of a host are currently lacking. We previously reported that quorum sensing regulates the virulence of Vibrio harveyi in a standardised model system with gnotobiotic brine shrimp (Artemia franciscana) larvae. Here, we monitored quorum sensing activity in Vibrio harveyi during infection of the shrimp, using bioluminescence as a read-out. We found that wild-type Vibrio harveyi shows a strong increase in quorum sensing activity early during infection. In this respect, the bacteria behave remarkably similar in different larvae, despite the fact that only half of them survive the infection. Interestingly, when expressed per bacterial cell, Vibrio harveyi showed around 200-fold higher maximal quorum sensing-regulated bioluminescence when associated with larvae than in the culture water. Finally, the in vivo quorum sensing activity of mutants defective in the production of one of the three signal molecules is consistent with their virulence, with no detectable in vivo quorum sensing activity in AI-2- and CAI-1-deficient mutants. These results indicate that AI-2 and CAI-1 are the dominant signals during infection of brine shrimp.     

细菌群体感应系统与噬菌体的相互作用机制研究进展

细菌在与噬菌体的长期共进化过程中形成多种抵抗噬菌体侵染的机制,其中群体感应参与的细菌抵御噬菌体侵染机制成为近年来的研究热点。群体感应与噬菌体之间的相互作用是复杂和多样的,本文将重点综述群体感应在噬菌体侵染中的作用、调控在噬菌体裂解-溶源转变的作用,以及群体感应与噬菌体的其他相互影响等内容,为噬菌体在细菌性疾病的治疗提供理论依据。     

群感效应与链霉菌次生代谢调控

群感效应是细菌协调群体行为的一种外界信号传递机制,在细菌中普遍存在,参与细胞的多种生理过程。链霉菌中也存在群感效应,在抗生素等次生代谢产物的生物合成中起重要的调控作用;从自诱导信号分子的结构到信号传递机制都存在一定多样性,其中以A-因子为代表的γ-丁酸内酯类信号分子的作用机制研究最为深入。近几年在链霉菌中发现的PI-因子、M-因子以及一些特定的代谢产物则代表几类结构较新颖的信号分子,通过群感效应机制调控次生代谢过程;链霉菌中还发现胆固醇氧化酶、甘油等分子具有信号分子特征,不排除是通过群感效应来参与抗生素生物合成调控。本文主要就参与链霉菌次生代谢调控的几类群感效应系统的研究状况进行综述,重点阐述各类群感信号分子的结构和信号传递机制的不同,并对链霉菌群感效应的研究趋势以及在抗生素高产菌遗传育种中的应用前景进行了展望。