Quantitative Lux-Based Assessment of Interacting Microbial Activity and Vadose Hydrology

该提案由环境地球化学和生物地球化学小组（征求NSF 96-2）审查，并由国家科学基金会的几个部门共同资助：分子和细胞生物科学、地球科学、环境生物学和数学科学。微生物在含水层以上非饱和介质中的动态时空分布基本上是未知的；尽管人们认识到分布可能是明显不均匀的。由于不饱和带的微生物群落降解了地球表面的绝大多数污染物，这种认识的缺乏对我们预测或增强这一基本污染物处理系统的能力产生了深刻的限制。这些研究涉及到一种分析方法的开发和应用，这种方法可以直接、连续地观察微生物的分布和活动，以及污染物通过异质不饱和多孔介质的输送。这可以通过地下水水文学和环境微生物学之间跨学科努力的两项新技术的统一来实现，即：(1)利用生物发光微生物来量化微生物活动和污染物运动；(2)利用透光室量化孔隙含水量、压力和水力流道。该系统采用一种萘降解细菌，荧光假单胞菌HK44，它有一个lux基因盒插入到萘降解途径中，使光的发射与萘或其代谢物水杨酸盐的降解率成正比。这些实验将在二维玻璃壁流动池中进行，其中包含两种尺度的含水层砂：2 x 1.5 m和60 x 60 cm。流动池提供受控的水通量，照明，以及整个实验的连续延时视频和数字CCD成像。地质非均质性的影响将通过用细砂和粗砂结构界面填充腔室来研究。这些研究将：1)确定在连续不饱和流动条件下，在均匀的多孔介质中是否会出现异质微生物定植区域。2)评价地质非均质性（质地变化）对微生物发育定位的影响。3)研究地质和生物异质性对污染物命运和迁移的联合和可能的相互作用。4)通过使用模拟水流和微生物栖息地的数值模型，根据本研究的实验结果，评估现有微生物和水动力理论的预测能力。这些研究将为科学和工程界了解自然和污染场所的地下微生物活动和生长提供强有力的新分析工具。在监测含水量和压力的同时，对微生物活动的速率和位置进行定量非破坏性观察的能力将大大提高利用微生物降解进行环境生物修复的能力。＊＊＊

9630293 Selker This proposal was reviewed by the Environmental Geochemistry and Biogeochemistry panel (solicitation NSF 96-2) and jointly funded by several divisions at the National Science Foundation: Molecular and Cellular Biosciences, Earth Science, Environmental Biology, and Mathematical Sciences. The dynamic temporal and spatial distribution of microbes in the unsaturated media above aquifers is essentially unknown; though it is recognized that the distribution can be significantly heterogeneous. Since microbial communities in the unsaturated zone degrade the vast majority of contaminants applied to the earth's surface, this lack in understanding presents profound limitations to our ability to predict or enhance this essential contaminant treatment system. These studies involve the development and application of an analytical methodology that allows for direct, continuous observation of microbial distribution and activity, as well as the transport of contaminants through heterogeneous unsaturated porous media. This is made possible through the unification of two new technologies in an interdisciplinary effort between groundwater hydrology and environmental microbiology, namely: (1) the utilization of bioluminescent microbes to quantify microbial activity and contaminant movement; and (2) the use of light transmission chambers to quantify pore water content, pressure, and hydraulic flow paths. The system employs a naphthalene-degrading bacterium, Pseudomonas flourescens HK44, which has a lux gene cassette inserted into the naphthalene degradation pathway such that light is emitted in direct proportion to the rate of degradation of naphthalene or its metabolite salicylate. These experiments will be carried out in two-dimensional glass-walled flow cells containing packed aquifer sands at two scales: 2 x 1.5 m and 60 x 60 cm. The flow cells provide for controlled aqueous flux, illumination, and continuous time-lapse video and digital CCD imaging of the entire experiment. The effect s of geologic heterogeneity will be studied by packing the chambers with fine over coarse sand textural interfaces. Theses studies will: 1) Determine if regions of heterogeneous microbial colonization develop in otherwise uniform porous media under continuous unsaturated flow conditions. 2) Evaluate the effect of geological heterogeneities (textural variation) on localization of microbial development. 3) Investigate the combined and possibly interacting effects of geological and biological heterogeneities on contaminant fate and transport. 4) Assess the predictive capabilities of present microbial and hydrodynamic theory with respect to the experimental results of this research through the use of numerical models which simulate flow and microbial habitat. These studies will provide a powerful new analytical tool for the scientific and engineering communities to gain understanding of subsurface microbial activity and growth in natural and contaminated sites. The ability to make quantitative non-destructive observations on the rate and position of microbial activity, while monitoring water content and pressure, will significantly increase the capability to exploit microbial degradation toward environmental bioremediation. ***