Response regulator output in bacterial chemotaxis

摘要: Chemotaxis responses in Escherichia coli are mediated by the phosphorylated response-regulator protein P-CheY. Biochemical and genetic studies have established mechanisms which various components of chemotaxis system, membrane receptors Che proteins function to modulate levels CheY phosphorylation. Detailed models been formulated explain sensing quantitative terms; however, cannot be adequately tested without knowledge relationship between P-CheY bacterial swimming behavior. A computerized image analysis system was developed collect extensive statistics on freeswimming individual tethered cells. were systematically varied controlled expression an E.coli strain lacking phosphatase, CheZ, receptor demethylating enzyme CheB. Tumbling frequency found vary with concentration a weakly sigmoidal fashion (apparent Hill coefficient approximately 2.5). This indicates that high sensitivity is not derived from highly cooperative interactions flagellar motor, but rather depends nonlinear effects within signal transduction network. The complex single flagella rotation free-swimming behavior examined; our results indicate there additional level information processing associated flagella. An allosteric model motor switching process proposed gives good fit observed induced Thus intracellular can estimated determinations: 30% pool appears fully adapted wild-type