微生物次生代谢的分子调控

摘要：微生物次生代谢产物在工业、农业和医药方面具有重要的应用价值,因此其合成调控长期以来倍受关注。近些年的研究表明,次生代谢产物的生物合成往往与产生菌的生理和发育状态紧密相关,其合成过程错综复杂,形成了多水平的调控网络。在目前所知的一万多种天然抗生素中, 约60%以上是链霉菌产生的。因此,本文主要以链霉菌产生的次生代谢产物为主线,以有突出进展的几种抗生素的研究为代表来介绍近年来抗生素生物合成中分子调控的相关进展,并对未来次生代谢合成调控的发展方向提出一点建议。     

链霉菌次生代谢中双因子调控系统的研究进展

链霉菌次生代谢产物的生物合成受到严格和复杂的调控,而双因子调控系统是其中重要的一类调控因子,在链霉菌中广泛存在,且存在作用方式的多样性和作用机制的复杂性。就近些年研究较多的参与链霉菌次生代谢的两类双因子调控系统(真核型和原核型)的研究状况做了综述,重点阐明其作用机制,并对其研究趋势以及在药物代谢工程中的应用前景进行了展望。     

链霉菌次级代谢调控相关的双组分系统研究进展

链霉菌具有强大的次级代谢能力, 能够产生众多具有生物活性的次级代谢产物, 如目前广泛应用的抗生素、抗肿瘤药物以及免疫抑制剂等。在链霉菌中, 次级代谢产物的生物合成受到包括途径特异性、多效性以及全局性调控基因在内的多层次严格调控。关键调控基因的缺失或过表达可以显著影响次级代谢产物的生物合成, 提示对于链霉菌次级代谢重要调控基因的功能及其作用机制的研究具有巨大的潜在应用价值。其中, 作为细菌信号传导系统的双组分系统(Two-component system, TCS)一直是大家研究的关注点。越来越多的研究表明TCS在链霉菌次级代谢过程中发挥着全局性的调控功能。本文重点介绍链霉菌模式菌株——天蓝色链霉菌中TCS(包括典型TCS)、孤立的组氨酸蛋白激酶(HK)以及应答调控蛋白(RR)参与次级代谢调控的研究进展。这些TCS的功能鉴定及机制解析为工业链霉菌的定向遗传改造以提高重要次级代谢产物的含量提供了理论依据。     

几种重要植物次生代谢防御反应物质的生物合成途径及分子调控机制研究进展

参与植物防御反应相关的次生代谢产物主要有酚类、萜类和生物碱类.近几年,随着转录组学、蛋白组学及新的分子生物学技术的广泛应用,极大地推进了植物次生代谢防御反应物质调控机制的研究进展.我们从这几类次生代谢物质的合成途径及其参与植物防御反应的分子调控机制两大方面进行概述,重点介绍这三类具有防御作用的次生代谢产物的生物合成途径、参与介导植物防御反应的相关信号分子及其转录调控机制,为正确认识植物次生代谢防御反应提供理论据.     

天蓝色链霉菌中抗生素合成相关双组分调控系统AfsQ1/Q2上游信号传导机制的研究

链霉菌是重要的工业微生物,能够合成众多具有生物活性的次级代谢产物,如抗生素、抗肿瘤药物以及免疫抑制剂等.次级代谢产物的合成受到多层次严格调控,深入开展相关机制研究将对工业菌株的高效育种提供重要理论指导.链霉菌中存在的两类关键信号传导系统,包括双组分系统(two-component system,TCS)和胞质外功能σ因子(extracytoplasmic function σ,ECF-σ),它们在次级代谢过程中发挥着重要的调控功能,但至今对于它们如何协同调控次级代谢的分子机制知之甚少.在前期研究工作中,我们在链霉菌模式菌株——天蓝色链霉菌中鉴定了一个参与抗生素生物合成调控的基因簇sigQ-afsQ1-4,其中sigQ编码ECF-σ因子(σ^Q),afsQ1/Q2编码一对TCS,afsQ3/Q4分别编码脂蛋白和跨膜蛋白.研究证实,TCS AfsQ1/Q2为抗生素生物合成的激活因子,sigQ的转录受到AfsQ1/Q2的直接调控,但σ^Q的功能正好相反,参与抗生素合成的负调控,即σ^Q对AfsQ1/Q2的功能存在拮抗作用.在前期工作...     

信号分子在链霉菌天然产物发现和开发中的应用研究进展

链霉菌具有巨大的合成次级代谢产物的潜力,但在实验室常规培养条件下链霉菌中大部分生物合成基因簇是沉默的,或者表达量极低。链霉菌中信号分子可调节形态分化和代谢产物的生物合成。通过对编码这些信号分子合成酶或受体的基因进行操作,或在发酵液中添加信号分子,可以激活链霉菌中的沉默生物合成基因簇,发现新的天然产物,或者提升已发现的天然产物产量。本文以γ-丁内酯和γ-丁烯内酯两类信号分子为例总结了过去十余年中信号分子在链霉菌天然产物发现和产量提升中的应用,以期为微生物天然产物的开发提供借鉴。     

圈卷产色链霉菌分化关键基因——saw1的克隆及酶切分析

链霉菌是现代生物学研究中一种重要的微生物,它有两个突出的特征:其一,有无与伦比的合成次生代谢产物的能力,世界上所知数千种抗生素的70％由其产生。其二,有一个复杂的发育分化的生命周期,是微生物分化研究的一个最好的模式材料。链霉菌分化主要为形态分化和生理分化,两者彼此独立又相互关联,构成复杂的分化调控网络,研究分化基因的调控不但有重要的理论意义,而且可用于控制抗生素的生物合成,因此弄清合成途径的分子机制,也有潜在的应用价值。圈卷产色链霉菌是从我国东北土     

链霉菌的全局调控蛋白DasR

链霉菌能够产生多种次级代谢产物,在临床、农牧业、生物技术等领域具有重要应用价值;对链霉菌的调控网络进行深入研究有助于提高次级代谢产物产量并发现新的次级代谢产物.链霉菌中次级代谢产物生物合成按调控通路分为全局调控与途径特异性调控,其中全局调控蛋白可靶向多种通路特异调控基因和生物合成基因,在链霉菌的生命活动中发挥着更为普遍...     

无机磷酸盐对链霉菌合成次级代谢产物的影响

链霉菌一个突出的特征是具有合成丰富的次级代谢产物的能力,许多次级代谢产物,如抗生素、免疫抑制剂、抗癌物质等在临床医药、水产养殖业等领域具有重要的应用价值。链霉菌次级代谢产物的合成常与环境中的营养因子有着密切的关系,在代谢水平上综述了无机磷酸盐对链霉菌合成次级代谢产物的影响,并在转录水平上阐释了双组分信号转导系统PhoR-PhoP的分子调控机制。PhoR-PhoP能够感应环境中的无机磷酸盐信号,当无机磷酸盐的浓度低于一定"阈值"时,PhoP蛋白作为主导的调控因子将抑制参与中心代谢和次级代谢等一系列基因的转录表达,减慢磷酸盐的消耗,并激活磷酸盐的摄取和转运系统及时补充胞内的磷酸盐,最终影响链霉菌次级代谢产物的合成和形态发育分化。     

LuxS quorum sensing: more than just a numbers game

Quorum sensing is a process of bacterial cell-to-cell communication involving the production and detection of extracellular signaling molecules called autoinducers. Quorum sensing allows populations of bacteria to collectively control gene expression, and thus synchronize group behavior. Processes controlled by quorum sensing are typically ones that are unproductive unless many bacteria act together. Most autoinducers enable intraspecies communication; however, a recently discovered autoinducer AI-2 has been proposed to serve as a 'universal signal' for interspecies communication. Studies suggest that AI-2 encodes information in addition to specifics about cell number.     

Molecular insights into quorum sensing in the human pathogen Pseudomonas aeruginosa from the structure of the virulence regulator LasR bound to its autoinducer

Many Gram-negative bacteria communicate via molecules called autoinducers to coordinate the activities of their populations. Such communication is termed quorum sensing and can regulate pathogenic virulence factor production and antimicrobial resistance. The quorum sensing system of Pseudomonas aeruginosa is currently the most intensively researched, because this bacterium is an opportunistic human pathogen annually responsible for the death of thousands of cystic fibrosis sufferers and many other immunocompromised individuals. Quorum sensing inhibitors can attenuate the pathogenicity of P. aeruginosa. Here we present the crystal structure of the P. aeruginosa LasR ligand-binding domain bound to its autoinducer 3-oxo-C(12)-acylhomoserine lactone. The structure is a symmetrical dimer, with each monomer exhibiting an alpha-beta-alpha fold similar to the TraR and SdiA quorum sensing proteins of Agrobacterium tumefaciens and Escherichia coli. The structure was determined up to 1.8-A resolution and reveals the atomic interactions between LasR and its autoinducer. The monomer structures of LasR, TraR, and SdiA are comparable but display differences in their quaternary organization. Inspection of their binding sites shows some unexpected variations resulting in quite different conformations of their bound autoinducers. We modeled interactions between LasR and various quorum sensing inhibitors, yielding insight into their possible mechanisms of action. The structure also provides a platform for the optimization, or de novo design, of quorum sensing inhibitors.     

How bacteria talk to each other: regulation of gene expression by quorum sensing

Quorum sensing, or the control of gene expression in response to cell density, is used by both gram-negative and gram-positive bacteria to regulate a variety of physiological functions. In all cases, quorum sensing involves the production and detection of extracellular signalling molecules called autoinducers. While universal signalling themes exist, variations in the design of the extracellular signals, the signal detection apparatuses, and the biochemical mechanisms of signal relay have allowed quorum sensing systems to be exquisitely adapted for their varied uses. Recent studies show that quorum sensing modulates both intra- and inter-species cell-cell communication, and it plays a major role in enabling bacteria to architect complex community structures.     

Bacteroides species produce Vibrio harveyi autoinducer 2-related molecules

Quorum sensing is a density-dependent gene regulation mechanism that has been described in many bacterial species in the last decades. Bacteria that use quorum sensing as part of their gene regulation circuits produce molecules called autoinducers that accumulate in the environment and activate target genes in a quorum-dependent way. Some specific clues led us to hypothesize that Bacteroides species can produce autoinducers and possess a quorum sensing system. First, Bacteroides are anaerobic bacteria that are frequently involved in polymicrobial infections. These infections often involve Pseudomonas aeruginosa and Staphylococcus aureus, two of the best understood examples of bacteria that employ quorum sensing systems as part of their pathogenesis. Also, studies have detected the presence of a quorum sensing gene involved in the production of autoinducers in Porphyromonas gingivalis, a species closely related to the Bacteroides genus. These and other evidences prompted us to investigate if Bacteroides strains could produce autoinducer molecules that could be detected by a Vibrio harveyi reporter system. In this paper, we show that supernatants of B. fragilis, B. vulgatus and B. distasonis strains are able to stimulate the V. harveyi quorum sensing system 2. Also, we were able to demonstrate that the stimulation detected is due to the production of autoinducer molecules and not the growth of reporter strains after addition of supernatant. Moreover, the phenomenon observed does not seem to represent the degradation of repressors possibly present in the culture medium used. We could also amplify bands from some of the strains tested using primers designed to the luxS gene of Escherichia coli. Altogether, our results show that B. fragilis, B. vulgatus and B. distasonis (but possibly some other species) can produce V. harveyi autoinducer 2-related molecules. However, the role of such molecules in the biology of these organisms remains unknown.     

根瘤菌与群体感应

细菌在高细胞密度下可以产生群体感应信号分子,调控细菌相关基因的表达,这种信号分子被称为自体诱导物。酰基高丝氨酸内酯类化合物(acyl-HSLs)是在根瘤菌中广泛存在的一类自体诱导物,该群体感应系统与根瘤菌和植物的共生作用密切相关。本文概述了AHLs介导的群体感应系统的组成及调控机制和不同根瘤菌中群体感应调节对根瘤菌生理行为及共生固氮的影响。     

Quorum sensing: How bacteria can coordinate activity and synchronize their response to external signals?

Quorum sensing is used by a large variety of bacteria to regulate gene expression in a cell-density-dependent manner. Bacteria can synchronize population behavior using small molecules called autoinducers that are produced by cognate synthases and recognized by specific receptors. Quorum sensing plays critical roles in regulating diverse cellular functions in bacteria, including bioluminescence, virulence gene expression, biofilm formation, and antibiotic resistance. The best-studied autoinducers are acyl homoserine lactone (AHL) molecules, which are the primary quorum sensing signals used by Gram-negative bacteria. In this review we focus on the AHL-dependent quorum sensing system and highlight recent progress on structural and mechanistic studies of AHL synthases and the corresponding receptors. Crystal structures of LuxI-type AHL synthases provide insights into acyl-substrate specificity, but the current knowledge is still greatly limited. Structural studies of AHL receptors have facilitated a more thorough understanding of signal perception and established the molecular framework for the development of quorum sensing inhibitors.     

Interference of Cranberry Constituents in Cell–Cell Signaling System of <Emphasis Type="Italic">Vibrio harveyi</Emphasis>

Cranberry juice has long been recognized in folk medicine as a therapeutic agent, mainly in urinary track infections. It acts as an antibiofilm agent against various pathogens. Quorum sensing is process where bacteria communicate with each other via signal molecules known as autoinducers. This process is strongly involved in various bacterial pathological and physiological pathways. Various strains of Vibrio harveyi bacteria were incubated with different concentrations of nondialyzable material of cranberry (NDM) with or without addition of exogenous autoinducer. Bioluminescence regulated by the autoinducers was measured in GENios reader. Effect of NDM alone or NDM supplemented with autoinducer on quorum sensing was determined as change in bioluminescence in each treated sample compared to appropriate control in every strain. Using model of V. harveyi, we found an inhibitory effect of cranberry constituents on bacterial signaling system. This effect was reversible, since exogenous autoinducer was able to recover bioluminescence which was decreased by NDM. We hypothesized that cranberry NDM interacts with V. harveyi quorum sensing by competition with autoinducer for binding to autoinducer sensor.     

细菌群体感应信号分子与抑制剂研究进展

具有群体感应系统的细菌通过相互交换一种自动诱导（autoinducer）信号分子来实现彼此问的信息交流。当信号分子积累到一定浓度时会改变细菌特定基因的表达,如生物膜的形成、生物发光行为、毒性基因的表达、孢子的形成等。近年来,人们发现了多种天然或者人工合成的群体感应抑制剂,可以干扰群感系统的信息回路。本文系统地阐述了细菌群体感应信息系统的划分、自体诱导分子及其抑制剂的研究进展。     

细菌的信息交流

细菌与细菌之间的信息交流是通过相互交换一种自动诱导物(autoinducer)的信号分子来实现的。这种信息交换的过程被称为群体感应(quorumsystem)。细菌根据这种特定信号分子浓度的变化来监测环境中其它细菌数量的变化。细菌的群体感应系统分为种内和种间信息交流两大类。细菌间的信息交流涉及到细菌的多种生理功能,如细菌的致病能力等。因此研究细菌间的信息交流有可能找到一条新的防治细菌感染途径。     

细菌的信息交流

细菌与细菌之间的信息交流是通过相互交换一种自动诱导物(autoinducer)的信号分子来实现的.这种信息交换的过程被称为群体感应(quorum system).细菌根据这种特定信号分子浓度的变化来监测环境中其它细菌数量的变化.细菌的群体感应系统分为种内和种间信息交流两大类.细菌间的信息交流涉及到细菌的多种生理功能,如细菌的致病能力等.因此研究细菌间的信息交流有可能找到一条新的防治细菌感染途径.