POWRE: Microscale Mechanisms in Unsaturated Biofilm Substrate Availability: A Molecular Reporter System Approach

霍尔顿陆地不饱和带中的细菌存在于生物膜中：附着在表面上并封装在微生物产生的外聚合物物质（EPS）的水合基质中。EPS基质代表传质区域，将细菌彼此分离并与外部孔隙环境分离。通过EPS的碳基质的质量转移可能会决定当地的碳周转率，但鲜为人知的是，在不饱和环境中的EPS及其对当地的基板可用性的影响。如果我们要了解控制有机物和污染物分解在不饱和系统作为气候或其他环境变化的函数，我们必须首先了解微生物生物膜的规模上的基板可用性的控制。这项研究将：1）确定生物乳化蛋白质在不饱和生物膜中的产生和作用，其中对培养物中蛋白质产生的控制是已知的; 2）确定生物膜传质区的作用及其对弱溶性底物代谢速率的控制; 3）确定水势对乳化剂产生、EPS传质特性和弱溶性底物的细菌代谢的影响;和4）开发和测试用于实验室和现场研究的弱可溶性底物的细菌生物传感器。这项由POWRE支持的研究将通过研究在特别具有挑战性但极其重要的空间分辨率尺度下运行的机制，提供不饱和系统中细菌微环境的基础知识。

9805946 Holden Bacteria in the terrestrial unsaturated zone exist in biofilms: attached to surfaces and encapsulated in a hydrated matrix of microbially-produced exopolymeric substances (EPS). The EPS matrix represents a mass transfer region, separating bacteria from one another and from the external pore environment. Mass transfer of carbon substrates through EPS may determine local rates of carbon turnover, but little is known about EPS in unsaturated environments and its effects on local substrate availability. If we are to understand the controls on organic matter and pollutant decomposition in unsaturated systems as a function of climatic or other environmental variations, we must first understand the controls on substrate availability at the scale of microbial biofilms. This research will: 1) determine the production and role of a bioemulsifying protein in unsaturated biofilms where the controls on protein production in culture are known; 2) determine the role of biofilm mass transfer region and its control on the rate of weakly soluble substrate metabolism; 3) determine the influence of water potential on emulsifier production, EPS mass transfer characteristics, and bacterial metabolism of weakly soluble substrates; and 4) develop and test a bacterial biosensor of weakly soluble substrates for use in lab and field studies. This POWRE-supported research will provide fundamental knowledge of the bacterial micro-environment in unsaturated systems, by studying mechanisms that operate at particularly challenging, but extremely important spatial scales of resolution.