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

9805946陆地非饱和带中的霍尔登细菌存在于生物膜中：附着在表面，并包裹在微生物产生的胞外聚合物的水合基质中。EPS基质代表一个传质区域，将细菌彼此分开，并与外部孔隙环境分开。碳基质通过EPS的质量转移可能决定局部的碳周转速率，但对EPS在非饱和环境中的作用及其对局部基质利用率的影响知之甚少。如果我们想要了解作为气候或其他环境变化的函数对非饱和系统中有机物和污染物分解的控制，我们必须首先了解在微生物生物膜尺度上对基质有效性的控制。这项研究将：1)确定在已知控制培养中蛋白质生产的不饱和生物膜中生物乳化蛋白质的产生和作用；2)确定生物膜传质区域的作用及其对弱溶底物代谢速率的控制；3)确定水势对乳化剂生产、EPS传质特性和弱溶底物细菌代谢的影响；以及4)开发和测试用于实验室和现场研究的弱溶底物细菌生物传感器。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，提供关于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.