CELL-CELL SIGNALLING IN MICROBE-HOST INTERACTIONS

微生物-宿主相互作用中的细胞-细胞信号传导

• 批准号: 2415301
• 负责人: Stephen Kendall Farrand
• 金额: $ 21.57万
• 依托单位: UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-05-01 至 1999-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2415301
• 关键词: Agrobacterium tumefaciens; DNA footprinting; bacterial genetics; bacterial virus; biological signal transduction; cell cell interaction; gene expression; gene induction /repression; gene interaction; genetic mapping; genetic promoter element; genetic regulation; host organism interaction; lactones; northern blottings; plasmids; serine; site directed mutagenesis; virulence; western blottings

Microorganisms that associate with higher eucaryotes, be they commensals, symbionts or pathogens, are generally well-adapted to the niche provided by their host. Included in their genetic repertoire are systems that allow them to sense host factors and to use these signals to invoke behavioral responses appropriate to the interaction. It also has become clear recently that the individual cells of a microbial community can communicate with each other via chemical signals. This communication system can lead to genetic changes that are favorable to the microbe on a community scale. One such microbe-microbe signalling mechanism, called autoinduction, recently was found to play a key role in regulating the interactions between certain pathogenic bacteria and their animal and plant hosts. In this system, the bacteria secrete a small homoserine lactone derivative called autoinducer (HSL-AI). Induction of genes required for virulence is dependent upon the accumulation of this signal molecule. If this is blocked, the bacteria generally cannot cause disease. Thus, if we understood how this signalling process works, we conceivably could develop treatments that specifically block the pathway. As antibiotics become less effective, we must consider all options in our efforts to develop new antimicrobial agents. The plant pathogen, Agrobacterium tumefaciens is an excellent organism in which to study microbe-host and microbe-microbe signalling systems. As part of the interaction with its host, A. tumefaciens senses a set of specific signals produced by the diseased plant and responds by elaborating its own HSL-AI mediated cell-cell signalling system. When this second messenger accumulates to a critical level, it triggers a change in the bacterial community leading to the conjugal transfer of a virulence plasmid from the bacterial pathogen to non-pathogenic relatives. Thus, the signal potentiates the spread of the virulence plasmid among the agrobacteria in the soil. The HSL-AIs function as co-inducers to gene activator proteins. Many different microorganisms utilize these HSL messengers, but a given bacterium may recognize only its cognate signal. Specificity is conferred by relatively minor differences in the structures of the AIs. The basis for this specificity at the molecular level is not known. Nor is the mechanism by which the HSL-AI acts as a transcriptional co-inducer. We propose to examine some of these problems in the Agrobacterium system. The basis for HSL-M specificity will be tested by domain switching experiments, and by isolation of mutants that can respond to other, non- cognate HSLs. The influence of the HSL on the ability of the activator protein to bind DNA will be assessed using the in vivo P22 challenge phage system. The mechanism by which the amino acid methionine specifically blocks the signal pathway will be determined by genetic analysis of resistant mutants, as well as physiological analysis of HSL-AI diffusion into and out of the cells. The role of a newly discovered component, ModA, in attenuating signal sensing will be examined by testing the ability of this protein to interact with the activator protein. Finally, the molecular mechanism by which the plant signal activates the HSL-AI second message pathway resulting in gene induction will be examined by Northern analysis, promoter mapping, and transposon mutagenesis.

与较高桉树相关的微生物，无论是共生， 共生体或病原体通常适应于提供的利基市场 由他们的主人。他们的遗传曲目中包括在内的系统 他们感知宿主因素并使用这些信号来调用行为 适合互动的响应。这也变得清晰 最近，微生物群落的各个细胞可以 通过化学信号相互通信。这个交流 系统可以导致有利于微生物的遗传变化 社区规模。一种这样的微生物微生物信号传导机制，称为 自动诱导，最近被发现在调节 某些致病细菌与其动物以及 植物宿主。在这个系统中，细菌分泌一个小均丝氨酸 内酯衍生物称为自动诱导剂（HSL-AI）。诱导基因 毒力需要取决于此信号的积累 分子。如果被阻塞，细菌通常不会引起疾病。 因此，如果我们了解了该信号过程的工作原理，我们可以想象 可以开发专门阻止途径的治疗方法。作为 抗生素的效果降低，我们必须考虑我们的所有选择 开发新的抗菌剂的努力。 植物病原体，农杆菌Tumefaciens是一种极好的生物 研究微生物 - 主机和微生物微生物信号传导系统。作为 与宿主的一部分互动，A。Tumefaciens感应一组 病植物产生的特定信号，并通过 详细说明其自己的HSL-AAI介导的细胞 - 细胞信号传导系统。当这个 第二使者积累到关键水平，它触发了变化 细菌群落导致毒力的结合转移 从细菌病原体到非致病亲属的质粒。因此， 信号增强毒力质粒在 土壤中的农杆菌。 HSL-AIS充当基因激活蛋白的共同诱导剂。许多 不同的微生物利用这些HSL使者，但给定的 细菌只能识别其同源信号。赋予特异性 AIS结构的差异相对较小。基础 对于分子水平的这种特异性，尚不清楚。也不是 HSL-AI充当转录共同诱导剂的机制。我们 建议在农业系统中检查其中一些问题。这 HSL-M特异性的基础将通过域切换测试 实验，以及通过隔离可以对其他非 - 同源HSL。 HSL对激活剂能力的影响 将使用体内P22挑战噬菌体评估结合DNA的蛋白质 系统。氨基酸蛋氨酸专门的机制 阻止信号途径将通过遗传分析来确定 抗性突变体以及HSL-AI扩散的生理分析 进出细胞。新发现的组件Moda的作用 在衰减信号传感时，将通过测试能力来检查 该蛋白与激活蛋白相互作用。最后， 植物信号激活HSL-AI第二的分子机制 导致基因诱导的消息途径将由北部检查 分析，启动子映射和转座子诱变。