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

9630293 Selker该提案由环境地球化学和生物地球化学小组审查（征集NSF 96-2），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的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，这种分布可能是显着的异质性。由于不饱和带中的微生物群落降解了地球表面的绝大多数污染物，因此缺乏了解对我们预测或加强这一重要污染物处理系统的能力造成了深刻的限制。 这些研究涉及分析方法的开发和应用，该方法允许直接，连续观察微生物的分布和活性，以及污染物通过非均质不饱和多孔介质的运输。这是通过地下水水文学和环境微生物学之间的跨学科努力中的两项新技术的统一而实现的，即：（1）利用生物发光微生物来量化微生物活性和污染物运动;以及（2）使用光传输室来量化孔隙水含量，压力和水力流动路径。 该系统采用萘降解细菌荧光假单胞菌HK 44，其具有插入萘降解途径中的lux基因盒，使得光的发射与萘或其代谢物水杨酸盐的降解速率成正比。这些实验将在二维玻璃壁流动池中进行，流动池中装有两种尺寸的填充含水层砂：2 x 1.5 m和60 x 60 cm。流动池提供受控的水通量、照明和整个实验的连续延时视频和数字CCD成像。将通过用细砂与粗砂纹理界面填充腔室来研究地质非均匀性的影响。 这些研究将：1）确定在连续不饱和流动条件下，在其他均匀多孔介质中是否形成异质微生物定植的区域。2)评估地质异质性（结构变化）对微生物发育定位的影响。3)调查地质和生物异质性对污染物归宿和迁移的综合影响和可能的相互影响。4)通过使用模拟流动和微生物栖息地的数值模型，评估当前微生物和流体动力学理论对本研究实验结果的预测能力。 这些研究将为科学界和工程界提供一个强有力的新分析工具，以了解自然和污染场地的地下微生物活动和生长情况。在监测水含量和压力的同时，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. ***