Transport and Chemoreception of Aromatic Compounds by Pseudomonas putida

芳香族化合物是绿色植物木本组织的主要成分，在环境中含量丰富。大量的芳香族污染物也作为工业废物被排放到环境中。这些化合物中的许多可以被细菌分解，并且对芳香化合物生物降解的酶学已经有了一定的了解。相比之下，人们对细菌如何从环境中寻找和获取芳香底物知之甚少；由趋化性和运输控制的过程。这个项目将检查这些知之甚少的方面的生物降解由细菌恶臭假单胞菌。研究将集中在PcaK，一种似乎具有4-羟基苯甲酸盐化学受体和渗透酶双重功能的蛋白质。pcaK基因与4-羟基苯甲酸酯生物降解基因协同调控。PcaK在浓度梯度下积累4-羟基苯甲酸，是芳香酸转运蛋白的第一个例子。在趋化性实验中，由于恶臭假单胞菌的PcaK突变体不被4-羟基苯甲酸酯或相关化合物吸引，PcaK蛋白似乎也具有化学受体的功能。PcaK与已知的细菌化学感受器不同源，因此似乎代表了一种新的化学感受器。研究将探索PcaK可以通过不同于已知细菌趋化系统的机制启动对芳香族化合物的趋化反应所需的感觉信号的假设。研究将确定与PcaK相互作用的蛋白质，以影响向恶臭杆菌鞭毛传递感觉信息，从而引起趋化反应。该项目的目标是了解细菌如何感知环境污染物的存在并做出反应。这有助于阐明趋化性在将游动细菌招募到特定环境地点（包括被污染物污染的环境）中的作用。这项研究将使人们进一步了解细菌行为反应在人类工业废物生物降解中的作用。

Harwood 9603551 Aromatic compounds are abundant in the environment as major constituents of the woody tissues of green plants. Large quantities of aromatic pollutants have also been released into the environment as industrial waste products. Many of these compounds can be broken down by bacteria, and a reasonable amount is known about the enzymology of aromatic compound biodegradation. By contrast, little is known about how bacteria seek and acquire aromatic substrates from the environment; processes that are governed by chemotaxis and transport. This project will examine these poorly understood aspects of biodegradation by the bacterium Pseudomonas putida. Studies will focus on PcaK, a protein that appears to have dual functions as a 4-hydroxybenzoate chemoreceptor and permease. The pcaK gene is coordinately regulated with genes for the biodegradation of 4-hydroxybenzoate. PcaK accumulates 4-hydroxybenzoate against a concentration gradient and is the first example of a transport protein for aromatic acids. The PcaK protein also appears to function as a chemoreceptor because P. putida pcaK mutants are not attracted to 4-hydroxybenzoate or related compounds in chemotaxis assays. PcaK is not homologous to known bacterial chemoreceptors, and thus appears to represent a new kind of chemoreceptor. Research will explore the hypothesis that PcaK can initiate sensory signaling required for chemotactic responses to aromatic compounds by a mechanism distinct from known bacterial chemotaxis systems. Studies will be carried out to define proteins that interact with PcaK to effect transmission of sensory information to the flagella of P. putida to cause chemotactic responses. The goal of the project is to understand how bacteria sense and respond to the presence of environmental pollutants in their environment. This could aid in elucidating the role of chemotaxis in recruiting swimming bacteria to particular environmental sites, including those contaminated with pollutants. The res earch should lead to an increased understanding of the role of bacterial behavioral responses in the biodegradation of human industrial wastes.