The Role of Bacterial Chemotaxis in the Biodegradation of Naphthalene in Porous Media

艾特肯9807666 人们对通过原位过程补救受污染土壤和地下水的方法非常感兴趣，特别是如果补救可以通过自然过程，如土著微生物的生物降解来完成。 要正确评价和开发原位生物修复方法，重要的是要了解主要的物理，化学和生物过程。 生物过程可能是其中最不为人所知的。 研究人员和他的同事们专注于细菌趋化性在多孔介质中常见土壤污染物生物降解中的潜在作用。 他们研究了恶臭假单胞菌G7在由均匀玻璃珠组成的模型多孔介质中对萘（一种常见的土壤污染物）的生物降解。 通过比较趋化性野生型菌株和具有与野生型相同的固有萘降解动力学的不动或非趋化性突变菌株的萘矿化速率来评价趋化性的作用。 构建了一个数学模型，该模型结合了实验系统中最重要的化学和生物现象。 该模型是用来量化的趋化和随机运动系数的有机体作为玻璃珠的大小的函数，并评估随机运动和趋化运动在萘生物降解的相对影响。 土壤和地下水的化学污染在美国是一个巨大的问题。如果污染物质不必被挖掘或泵到地表进行处理或处置，那么清理污染场地的成本可以显著降低;因此，人们对利用被称为“自然衰减”的过程非常感兴趣。“已知地下发现的许多细菌能够降解各种化学物质，但对土壤中细菌的行为了解相对较少。 许多细菌的一个共同特性是趋化性，一种对化学物质的存在做出反应的能力。 然而，趋化性在土壤中污染物生物降解中的潜在作用尚未被探索。 例如，能够游向化学污染源的细菌可能比那些不能这样做的细菌更快地降解污染物。 该项目的研究人员利用模拟土壤环境和数学建模技术进行实验，以评估趋化性在许多污染场地发现的污染物生物降解中的潜在作用。 更好地了解趋化性的作用，将允许更好地表征自然衰减过程的可行性，并可能允许开发的战略，以加快利用细菌趋化性的污染场地的原位处理。

Aitken 9807666 There is considerable interest in methods of remediating contaminated soil and ground water by in situ processes, particularly if remediation can be accomplished through natural processes such as biodegradation by indigenous microorganisms. To properly evaluate and develop in situ bioremediation methods, it is important to understand the dominant physical, chemical and biological processes. Biological processes are perhaps the least understood of these. The investigator and his colleagues focus on the potential role of bacterial chemotaxis in the biodegradation of common soil pollutants in porous media. They study the biodegradation of naphthalene, a common soil pollutant, by Pseudomonas putida G7 in a model porous medium consisting of uniform glass beads. The effect of chemotaxis is evaluated by comparing the rates of mineralization of naphthalene by the chemotactic wild-type strain and by an immotile or non-chemotactic mutant strain with the same inherent kinetics of naphthalene degradation as the wild-type. A mathematical model is constructed that incorporates the most significant chemical and biological phenomena in the experimental system. The model is used to quantify the chemotactic and random motility coefficients of the organism as a function of the size of the glass beads, and to evaluate the relative influences of random motility and chemotactic motility in naphthalene biodegradation. Chemical contamination of soil and ground water is an enormous problem in the U.S. The cost of cleaning up contaminated sites can be reduced dramatically if the contaminated materials do not have to be excavated or pumped to the surface for treatment or disposal; consequently there is great interest in taking advantage of processes referred to as "natural attenuation." Many bacteria found in the subsurface are known to be able to degrade a variety of chemicals, but the behavior of bacteria in soil is relatively poorly understood. A commo n property of many bacteria is chemotaxis, an ability to move in response to the presence of a chemical. However, the potential role of chemotaxis in the biodegradation of pollutants in soil has not been explored before. It is likely, for example, that bacteria able to swim towards the sources of chemical contamination are able to degrade the contaminants faster than those bacteria unable to do so. The investigators in this project conduct experiments with a simulated soil environment and mathematical modeling techniques to evaluate the potential role of chemotaxis in the biodegradation of a pollutant found at many contaminated sites. An improved understanding of the role of chemotaxis will permit better characterization of the feasibility of natural attenuation processes, and may permit the development of strategies to accelerate the in situ treatment of contaminated sites that take advantage of bacterial chemotaxis.