Motile Escherichia coli can move toward or away from a variety of chemicals. The objective of the proposed research is to elucidate the machinery and information-processing strategies that underlie this chemotactic behavior. Mutants defective in chemotaxis will be employed to investigate the genetic basis of this behavior. Deletions of individual chemotaxis genes will be isolated by selecting for loss of polar effects caused by insertion mutations or by selecting deletions in specialized lambda-transducing phages that carry chemotaxis genes. The swimming and flagellar rotation patterns and response physiology of these deletion strains will be investigated to determine to null phenotypes of chemotaxis genes. The role of each gene will be studied by examining the epistatic relationships and functional interactions of different chemotaxis genes. Reversion studies will be carried out to detect functional suppressors of various chemotaxis defects and alternate pathways for handling sensory data. Mutants defective in sensory adaptation will also be studied to identify possible targets and regulators of the adaptation system. Finally, the role of protein cleavages in stimulus transduction and sensory adaptation will be investigated. Protein cleavage will be examined in chemotaxis mutants and their revertants to determine whether cleavage is necessary for chemotaxis, and if it is, what gene products are responsible for cleavage activity.