Bacterial motility and chemotaxis.
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This chapter summarizes the basic features of bacterial motility and chemotaxis. Bacterial chemotaxis represents one of the simplest behaviors that can be studied. Its popularity as an experimental system stems from several sources. The genetic and biochemical tools have been developed to investigate the biology of enteric bacteria. The motility and chemotaxis can be virulence factors for intestinal and urogenital-tract pathogens. Flagella constitute one of the most effective bacterial antigens and the immune system directs its counterattacks against it. Chemotaxis also occurs in bacteria within the rhizosphere and in aquatic environments. Polar flagella arise at the morphologically definable ends of rod-shaped or curved bacterial cells. Bacteria can move in two or in three dimensions. Those that move on surfaces without flagella exhibit gliding motility, whereas those that rely on flagella to move on surfaces exhibit swarming motility. Any movement in three dimensions is called swimming. Bacteria have chemoreceptors, namely, proteins that bind to the effector ligands in a stereospecific way. The bacteria sense spatial gradients by means of a temporal mechanism. In addition to being attracted to or repelled by specific chemicals, bacteria exhibit phototaxis, magnetotaxis, osmotaxis, galvanotaxis, and thermotaxis. The chapter also describes the chemoreceptor structure and ligand binding and outlines the subsequent steps in signal transduction. 1992, Academic Press Limited. All rights reserved.
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