Research Supplement to Promote Diversity in Microbiology

父项目摘要/摘要 这项拟议的项目将阐明控制极性粘附素产生的机制， 生理异质性α-蛋白细菌的生物膜形成和宿主定植 这包括一些重要的人类病原体。与公共卫生特别相关的生物膜 形态对细菌在不同环境中的生存起着至关重要的作用：生物膜中的细胞附着 对生物和非生物表面的顽固性，对抗菌剂的抗药性增加，以及 会导致持续性感染。尽管限制生物膜的形成有可能防止和 限制微生物疾病，对α-蛋白细菌生物膜的形成以及它是如何形成的知之甚少。 促进了宿主的殖民。 我们之前发现了一种与生物膜相关的突变，在实验室菌株中很常见 苜蓿中华根瘤菌--一种与亲和性形成互惠共生的模式α-蛋白细菌 通过定植根组织和固定氮素来换取植物寄主的养分的豆科植物。 纠正突变恢复了保守的极性因子PodJ的全长生产，因此 能够合成Holdfast(一种极性粘附素)和组装坚固的生物膜，表型从不 之前观察到的。我们发现，具有生物被膜能力的菌株比 宿主感染过程中的生物膜缺陷菌株。通过转座子诱变，我们鉴定了一些 参与生物膜发育的基因，包括编码保守转录因子(LdtR)的基因 另一种编码二鸟苷环化酶和磷酸二酯酶，已知可以调节 C-di-GMP第二信使。这项提案的目标是：(A)破译关键字的责任 生物膜形成和寄主定植过程中的调节器以及(B)建立监测系统 共生与环境因素的关系。我们计划通过以下方式实现这些目标 实现以下三个具体目标。(1)我们将确定LdtR的表达方式 以及它所执行的细胞功能。(2)我们将评估调节c-di的因素如何- GMP水平有助于生物膜的形成和宿主感染。(3)我们将评估共生 影响宿主对有毒化合物的反应，以及化学应激和其他微生物如何影响宿主- 共生体的相互作用。研究结果将提供一个更好的模型，说明细胞和 外部因素可促进黏附、生物被膜形成和宿主入侵。 变形杆菌。 除了实现上述科学目标外，对这项提案的资助 将提高研究效率和授予调查人员的竞争力，并允许学生， 特别是那些来自代表性不足的背景的人，以获得研究培训和准备 生物医学职业。 多样性补充摘要 行政补充将使属于某个团体的本科生 在生物医学科学中历史上代表不足的人进行两年的微生物学研究 萨默斯。学生将确定两个保守的细菌基因是否有助于提高效率 草地早熟禾与豆科寄主的共生关系。除了在实验室获得熟练程度之外 在技术和研究技能方面，学生将接受进入博士学位的指导和培训。 计划和科学生涯。

Parent Project Summary / Abstract The proposed project will elucidate the mechanisms that control polar adhesin production, biofilm formation, and host colonization in alpha-proteobacteria, a physiologically heterogeneous group that includes a number of significant human pathogens. Particularly relevant to public health, biofilm formation plays a crucial role in the survival of bacteria in diverse environments: cells in biofilms attach recalcitrantly to biotic and abiotic surfaces, develop increased resistance to antimicrobial agents, and contribute to persistent infections. Although limiting biofilm formation has the potential to prevent and restrict microbial diseases, little is known about biofilm formation by alpha-proteobacteria and how it facilitates host colonization. We previously discovered a biofilm-associated mutation common in laboratory strains of Sinorhizobium meliloti, a model alpha-proteobacterium that forms mutualistic symbiosis with compatible legumes by colonizing root tissues and fixing nitrogen in exchange for nutrients from plant hosts. Correcting the mutation restored full-length production of the conserved polarity factor PodJ, thus enabling synthesis of the holdfast (a polar adhesin) and assembly of robust biofilms, phenotypes never observed before. We found that biofilm-competent strains possess a competitive advantage over biofilm-deficient strains during host infection. Via transposon mutagenesis, we identified a number of genes involved in biofilm development, including one encoding a conserved transcription factor (LdtR) and another encoding a diguanylate cyclase and phosphodiesterase, known to modulate levels of the c-di-GMP second messenger. The goals of this proposal are (a) to decipher the responsibilities of key regulators during biofilm formation and host colonization and (b) to establish a system for monitoring the relationship between symbiosis and environmental factors. We plan to achieve these goals by accomplishing the following three specific aims. (1) We will determine how LdtR expression is regulated and what cellular functions it performs. (2) We will assess how factors that modulate c-di- GMP levels contribute to biofilm formation and host infection. (3) We will evaluate whether symbiosis affects host response to toxic compounds and how chemical stress and other microbes influence host- symbiont interactions. Results from the investigation will provide a better model of how cellular and external factors can contribute to adhesion, biofilm formation, and host invasion in alpha- proteobacteria. In addition to accomplishing the scientific objectives described above, funding of this proposal will enhance the research productivity and grant competitiveness of the investigator and allow students, particularly those from underrepresented backgrounds, to gain research training and preparation for biomedical careers. Diversity Supplement Summary The administrative supplement will enable an undergraduate student who belongs to a group historically underrepresented in the biomedical sciences to conduct microbiology research for two summers. The student will determine whether two conserved bacterial genes contribute to efficient symbiosis between S. meliloti and its legume hosts. In addition to gaining proficiency in laboratory techniques and research skills, the student will receive guidance and training on entry into a Ph.D. program and a scientific career.