CHEMOTAXIS IN BACILLUS-SUBTILIS - HOW BACTERIA MONITOR ENVIRONMENTAL SIGNALS

Virtually all organisms have means of monitoring their environment and making use of information gained to aid their survival. Many organism s, from bacteria to animals, move from place to place and can alter th eir movements. Chemotaxis is a signal transduction system found in mot ile bacteria that allows them to sense changes in the concentrations o f various extracellular compounds and change their swimming behavior i n a way that moves them toward more favorable environments. Chemotaxis is the most ancient sensory-motor process in nature. For years, studi es of enteric bacteria, such as Escherichia coil and Salmonella typhim urium, have served as the paradigm for understanding this process on a molecular level. Recent studies on the gram-positive bacterium, Bacil lus subtilis, and other bacteria, suggest that a slightly more complex system may be ancestral to that of the more extensively studied enter ics. Aspects of chemotaxis that are unique to B. subtilis include a mo re complex adaptation system, with protein-protein methyl group transf er, chemotaxis proteins having no counterparts in E. coil, and a very extensive repertoire of repellents that are sensed at very low concent rations by receptors.