Complementation analysis and deletion mapping of Escherichia coli mutants defective in chemotaxis.

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Abstract
Motile, but generally nonchemotactic (che) mutants of E. coli were examined for complementation and recombination with specialized .lambda.fla transducing phages. The complex complementation behavior of these mutants found previously in F-prime tests could largely be accounted for by intragenic complementation and by polarity effects. Mutants of the cheA class defined 2 genes, cheA and cheW, which appeared to be co-transcribed. Mutants of the cheB class defined four genes, cheX, cheB, cheY and cheZ, which also constituted a transcriptional unit. Mutants defective in cheA, cheW, cheX or cheY function swam smmothly, with little or no tumbling, but cheB or cheZ mutants exhibited very high tumbling rates. These functions are probably involved in initiating or controlling changes in flagellar rotation in response to chemotactic stimuli.