Transport and Chemoreception of Aromatic Compounds by Pseudomonas putida

点击翻译按钮获取中文摘要

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.