SC3: Regulation of polar adhesion during Sinorhizobium meliloti infection

 描述（由申请人提供）：拟议的项目将破译控制α-变形菌中粘附素生产和生物膜形成的分子机制，α-变形菌是一个生理异质性群体，包括许多导致严重人类疾病的病原体。生物膜的形成对细菌在不同环境中的生存起着至关重要的作用，并且与公共卫生密切相关。生物膜中的细胞粘附在 生物和非生物表面，发展对抗微生物剂的增加的抗性，并且促成持续性感染。虽然限制生物膜形成有可能预防和限制细菌感染，但对α-变形菌的生物膜形成及其如何促进宿主定植知之甚少。最近，我们发现了一个突变的保守的细胞极性因子PodJ在驯化的，实验室菌株的苜蓿中华根瘤菌-一个模型α-变形杆菌，建立互惠共生与兼容的豆科植物通过殖民他们的根组织和固定分子氮，以换取营养物质从宿主植物。修正突变并将PodJ极性因子恢复到环境中S.苜蓿草能够使Rm 1021实验室菌株产生一种称为holdfast的极性粘附素，并形成坚固的生物膜。此外，校正的等位基因（podJ+）在共生过程中赋予了竞争优势。这些新的表型从来没有被表征，因为常用的S。苜蓿属的所有菌株都具有该突变。这项提案的目标是阐明遗传电路，连接细胞周期依赖性 极性因子PodJ的调节生产的粘合剂holdfast，促进生物膜的形成，提高健身，特别是在主机殖民。实现这一目标涉及实现以下四个具体目标：（1）确定作为细胞周期的函数的PodJ和holdfast的亚细胞位置;（2）评估环境条件对holdfast合成和生物膜形成的影响;（3）评估holdfast是否增加对宿主组织的附着;以及（4）鉴定和定义参与holdfast产生的细胞因子的作用。从调查的结果将提供一个更好的模型，如何保守和物种特异性途径可以有助于粘附和生物膜形成的α-变形菌。这些知识将为开发对抗生物膜和细菌感染的新方法提供基础。除了完成科学目标 正如上文所述，这项建议的拨款将提高研究人员的研究生产力和资助竞争力，并让学生，特别是那些来自代表性不足背景的学生，有机会接触令人兴奋的研究领域，从而培养他们对生物医学事业的追求。

 DESCRIPTION (provided by applicant): The proposed project will decipher the molecular mechanisms that control adhesin production and biofilm formation in alpha-proteobacteria, a physiologically heterogeneous group that includes a number of pathogens that cause serious human diseases. Biofilm formation plays a crucial role in the survival of bacteria in diverse environments and is of great relevance to public health. 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 bacterial infections, little is known about biofilm formation by alpha-proteobacteria and how it facilitates host colonization. Recently, we discovered a mutation in the conserved cell polarity factor PodJ in domesticated, laboratory strains of Sinorhizobium meliloti -- a model alpha-proteobacterium that establishes mutualistic symbioses with compatible legumes by colonizing their root tissues and fixing molecular nitrogen in exchange for nutrients from host plants. Correcting the mutation and restoring the PodJ polarity factor to the version found in environmental isolates of S. meliloti enabled the Rm1021 laboratory strain to produce a polar adhesin, called holdfast, and to develop robust biofilms. Furthermore, the corrected allele (podJ+) conferred a competitive advantage during symbiosis. These novel phenotypes have never been characterized because commonly used S. meliloti strains all possess the mutation. The goal of this proposal is to elucidate the genetic circuitry that links the cell cycle-dependent polarity factor PodJ to the regulated production of adhesive holdfast, which promotes biofilm formation and enhances fitness, particularly during host colonization. Achieving this goal involves accomplishing the following four specific aims: (1) determine the subcellular locations of PodJ and holdfast as a function of the cell cycle; (2) evaluate environmental conditions for their effects on holdfast synthesis and biofilm formation; (3) assess if holdfast increases attachment to host tissue; and (4) identify and define the roles of cellular factors that participae in holdfast production. Results from the investigation will provide a better model of how conserved and species-specific pathways can contribute to adhesion and biofilm formation in alpha-proteobacteria. Such knowledge will provide the foundation for developing new methods to combat biofilms and bacterial infections. 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 exposure to an exciting area of research, thus nurturing their pursuits of biomedical careers.