Does Composition of the Exopolysaccharide Matrix of Pseudomonas Putida Control Biofilm Architecture and Fitness In Low-water-content Environments?

恶臭假单胞菌胞外多糖基质的组成是否控制低含水量环境中的生物膜结构和适应性？

• 批准号: 0446292
• 负责人: Larry Halverson
• 金额: $ 43.5万
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-15 至 2009-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0446292&HistoricalAwards=false
• 关键词: Does; Composition; Exopolysaccharide; Matrix; Pseudomonas

Intellectual Merit: Bacteria in soil and other unsaturated habitats, such as lungs or aerial surfaces of plants, generally live as aggregates of cells (biofilms) within a matrix comprised, in part, of extracellular polysaccharides (EPS) of their own making. Although there is general agreement that bacteria in many environments, including aquatic biofilm communities, live within an EPS matrix, relatively little is known about the function of the EPS layer in general or even specific polysaccharide components of the matrix. One possibility that has been often discussed but has been the subject of relatively few studies is that an EPS envelope may protect bacteria from drying, thus functioning as a fitness trait in low water content habitats. Soil microorganisms mediate many critical terrestrial ecosystem processes, including global biogeochemical cycles, the degradation of organic pollutants, and beneficial and detrimental interactions with plants, yet we still have a poor understanding of how water availability influences biofilm development and metabolic activities and the survival of community members. The goal of this project is to understand the processes involved in bacterial colonization of soil and how the environment influences bacterial fitness, including the mechanisms by which environmental cues are integrated into the regulatory networks involved in adaptation to those stresses. The central hypothesis that serves as a framework for this project is that the availability of water to bacteria is a major force influencing bacterial physiology, growth, and survival. The hypotheses that will be tested are that modulation of the composition of the EPS matrix is an active process that is driven by dehydration stress and that specific EPS constituents hold substantial amounts of water thereby creating a microenvironment that slows the rate of biofilm drying, which increases bacterial survival by increasing the time for metabolic adjustment. Furthermore, stress-mediated modulation of the EPS matrix alters biofilm developmental processes and architecture, which ultimately influences the biophysical properties of the biofilm and the metabolic capabilities of community members. The objectives of the project are to: 1, identify genes involved in extracellular polysaccharide biosynthesis, assess their regulation and inactivate them; 2, assess whether extracellular polysaccharides create a more hydrated microenvironment that protects biofilm cells from desiccation stress; and 3, assess the role of EPS on biofilm developmental patterns and architecture in low water content habitats.Broader impacts: An important component of this research is to fill a major gap in our understanding of biofilm biology in terrestrial ecosystems, which has had to typically rely on information obtained from experimental systems that frequently don't reflect soil conditions. This project will provide multiple opportunities for research training coupled to instruction and to promote inquiry based learning strategies. Students will be challenged to identify linkages of this project to regulatory hierarchies and signal transduction pathways and to the broader implications of these growth forms on terrestrial ecosystem processes. Information will be disseminated through publications and presentations at meetings and through a website that will contain images and descriptions of unsaturated biofilm development and properties that are not available in publication format. Furthermore, the results and experimental methodologies will be incorporated into the undergraduate microbiology curriculum into new lecture and laboratory courses the PI is currently developing.

智力优势： 土壤和其他不饱和栖息地（如肺或植物的空气表面）中的细菌通常作为细胞聚集体（生物膜）生活在基质中，部分由其自身产生的胞外多糖（EPS）组成。尽管人们普遍认为，许多环境中的细菌，包括水生生物膜群落，生活在EPS基质中，但对EPS层在一般或甚至基质的特定多糖组分中的功能知之甚少。一种经常被讨论但研究相对较少的可能性是，EPS包膜可以保护细菌免受干燥，从而在低含水量的栖息地中发挥适应性特征的作用。土壤微生物介导了许多关键的陆地生态系统过程，包括全球土壤地球化学循环，有机污染物的降解，以及与植物的有益和有害相互作用，但我们仍然对水的可用性如何影响生物膜的发育和代谢活动以及社区成员的生存了解甚少。该项目的目标是了解细菌在土壤中定植的过程以及环境如何影响细菌的适应性，包括环境线索整合到适应这些压力的调控网络中的机制。作为该项目框架的中心假设是，细菌对水的可用性是影响细菌生理学，生长和存活的主要力量。将测试的假设是，EPS基质的组成的调节是由脱水应激驱动的主动过程，并且特定的EPS成分保持大量的水，从而产生减缓生物膜干燥速率的微环境，这通过增加代谢调节的时间来增加细菌存活。此外，应激介导的EPS基质的调节改变生物膜发育过程和结构，这最终影响生物膜的生物物理性质和群落成员的代谢能力。该项目的目标是：1，确定参与胞外多糖生物合成的基因，评估其调控并对其进行测序; 2，评估胞外多糖是否创造了一个更水合的微环境，保护生物膜细胞免受干燥胁迫; 3，评估EPS对低含水量栖息地生物膜发育模式和结构的作用。 这项研究的一个重要组成部分是填补我们对陆地生态系统中生物膜生物学的理解中的一个主要空白，这通常不得不依赖于从实验系统中获得的信息，而这些信息往往不能反映土壤条件。该项目将为研究培训提供多种机会，并促进基于探究的学习策略。学生将面临的挑战，以确定该项目的监管层次和信号转导途径的联系，这些增长形式对陆地生态系统过程的更广泛的影响。信息将通过出版物和会议上的介绍以及通过一个网站传播，该网站将包含出版物格式中无法获得的不饱和生物膜发展和特性的图像和描述。此外，研究结果和实验方法将被纳入到本科微生物学课程到新的讲座和实验室课程的PI目前正在开发。