Bacterial Chemotaxis to Aromatic Hydrocarbons and Related Pollutants

趋化性是指活动细菌检测环境中特定化学物质并作出反应的能力，它们会沿着引诱剂化合物的梯度向上移动，远离驱避剂。尽管各种细菌似乎都有保守的趋化性信号转导系统，但土壤细菌似乎比研究充分的肠道细菌具有更复杂的化学感觉系统。例如，大肠杆菌等肠道细菌具有相对少量的甲基接受趋化蛋白（MCPs），这可能反映了它们所处生态位中存在的可用碳源的范围。相比之下，假单胞菌属成员的可用测序基因组具有26至49个注释mcp样蛋白。土壤细菌，如假单胞菌，以其分解代谢多样性而闻名，并且具有如此大量的mcp，它们似乎具有同样广泛的化学感觉系统。然而，很少有研究试图描述土壤细菌的趋化反应范围或鉴定特定的趋化受体。本研究的重点是环境污染物的生物降解与降解细菌通过使用特定的趋化系统感知这些有毒化学物质的能力之间的关系。该项目的总体目标是表征生物降解细菌对芳香烃和相关污染物的趋化反应。分解代谢多样的芳香烃降解细菌恶臭假单胞菌F1将作为这些研究的模式生物。P. putida F1具有对甲苯、苯、乙苯和对伞花烃等几种芳香烃的感知和化学反应能力，这些芳香烃都是该菌株的碳和能量来源。此外，该菌株还被氯代烃污染物三氯乙烯、顺式二氯乙烯和过氯乙烯所吸引。对这些化合物的反应是可诱导的——目前来自首席研究员实验室的数据表明，恶臭假单胞菌F1含有至少两种化学受体来介导这些反应。然而，目前对p.p putida F1对甲苯和相关污染物的趋化性的特异性受体还没有进一步的了解。该项目将研究p.p putida F1中芳香烃代谢、趋化性和基因表达之间的关系，主要关注甲苯和对花香烃的趋化反应。恶臭假单胞菌F1全基因组序列的获得将为这项工作提供便利。本研究获得的结果将增加我们对细菌化学感觉系统的广度以及细菌如何检测和响应有毒芳香烃和人造氯化烯烃的理解。更广泛的影响：本研究项目将有助于高中，本科生和研究生的教育和培训，为他们提供宝贵的研究经验。在加州大学戴维斯分校，该项目将为两名研究生提供研究经验，其中一名研究生将主要关注甲苯的趋化性，另一名则关注对聚伞烃的趋化性。兼职本科生研究人员将在学年期间在加州大学戴维斯分校从事该项目，加州大学戴维斯分校青年学者计划的高中生和夏季本科生研究计划的本科生也将参与该研究。在圣托马斯大学（UST），研究将被整合到生物学课程中，在新的生物信息学课程中，学生将在对这种有机体进行湿实验室研究项目时积极地注释p.p . putida F1基因组。暑期UST的学生将全职研究p.p putida F1的趋化性，每年夏天将有一名学生前往加州大学戴维斯分校，与从事该项目的研究生一起工作一个月。

Chemotaxis is the ability of motile bacteria to detect and respond to specific chemicals in the environment, moving up gradients of attractant compounds and away from repellents. Although diverse bacteria appear to have conserved chemotaxis signal transduction systems, soil bacteria seem to have more complex chemosensory systems than the well-studied enteric bacteria. For example, enteric bacteria such as Escherichia coli have a relatively small number of methyl-accepting chemotaxis proteins (MCPs), which is likely to reflect the range of available carbon sources present in the ecological niche in which they reside. In contrast, the available sequenced genomes of members of the genus Pseudomonas have between 26 and 49 annotated MCP-like proteins. Soil bacteria such as the pseudomonads are known for their catabolic diversity and with such a large number of MCPs, they appear to have equally broad chemosensory systems. However, few studies have attempted to characterize the range of chemotactic responses or identify specific chemoreceptors in soil bacteria. This research focuses on the relationship between the biodegradation of environmental pollutants and the ability of degradative bacteria to sense these toxic chemicals by using specific chemotaxis systems. The overall goal of this project is to characterize the chemotactic responses of a biodegradative bacterium to aromatic hydrocarbons and related pollutants. The catabolically versatile aromatic hydrocarbon-degrading bacterium Pseudomonas putida F1 will be used as the model organism for these studies. P. putida F1 has the ability to sense and respond chemotactically to several aromatic hydrocarbons including toluene, benzene, ethylbenzene, and p-cymene, all of which serve as carbon and energy sources for the strain. In addition, this strain is also attracted to the chlorinated hydrocarbon pollutants trichloroethylene, cis-dichloroethylene, and perchloroethylene. The responses to these compounds are inducible--current data from the Principal Investigator's laboratory indicate that P. putida F1 contains at least two chemoreceptors to mediate these responses. At this time, however, nothing further is known about the specific receptors involved in chemotaxis to toluene and related pollutants in P. putida F1. The project will investigate the relationship between aromatic hydrocarbon metabolism, chemotaxis, and gene expression in P. putida F1, focusing primarily on the toluene and p-cymene chemotactic responses. This work will be facilitated by the availability of the complete genome sequence of P. putida F1. The results obtained in this study will increase our understanding of the breadth of bacterial chemosensory systems and how bacteria detect and respond to toxic aromatic hydrocarbons and man-made chlorinated alkenes.Broader impacts: This research project will contribute to the education and training of high school, undergraduate, and graduate students, providing them with valuable research experience. At the University of California-Davis, the project will provide research experience for two graduate students, one of whom will focus primarily on toluene chemotaxis, and the other on p-cymene chemotaxis. Part-time undergraduate researchers will work on the project at UC Davis during the academic year, and high school students in the Young Scholars Program and undergraduates in the Summer Undergraduate Research Program at UC Davis will also participate in the research. At the University of St. Thomas (UST) research will be integrated into the Biology curriculum in a new Bioinformatics course in which students will actively annotate the P. putida F1 genome while they carry out wet laboratory research projects with this organism. Summer UST students will carry out full time research on chemotaxis in P. putida F1, and one student per summer will travel to UC Davis to work for one month with graduate students working on the project.