Effects of p-fluorophenylalanine and chloramphenicol on chemotaxis in Escherichia coli.

The effects of chloramphenicol and p-fluorophenylalanine (p-FPA) on growth, proportion of motile cells, average rate of motility, and the chemotactic response of a methionine auxotroph of Escherichia coli K-12 were studied. Kinetic studies revealed that the inhibition of chemotaxis by p-FPA can be explained by the effect on growth, proportion of motile cells, and average rate of motility rather than a selective inhibition of chemotaxis per se. The effect of chloramphenicol on chemotaxis could not be explained in terms of these characteristics. It is concluded that low concentrations of chloramphenicol, unlike p-FPA, selectively inhibit chemotaxis.