Motility and chemotaxis of filamentous cells of Escherichia coli

Filamentous cells of Escherichia coli can be produced by treatment with the antibiotic cephalexin, which blocks cell division but allows cell growth, To explore the effect of cell size on chemotactic activity, we studied the motility and chemotaxis of filamentous cells, The filaments, up to 50 times the length of normal E. coli organisms, were motile and had flagella along their entire lengths. Despite their increased size, the motility and chemo taxis of filaments were very similar to those properties of normal-sized ce lls. Unstimulated filaments of chemotactically normal bacteria ran and stop ped repeatedly (while normal-sized bacteria run and tumble repeatedly). Fil aments responded to attractants by prolonged running (like normal-sized bac teria) and to repellents by prolonged stopping (unlike normal-sized bacteri a, which tumble), until adaptation restored unstimulated behavior (as occur s with normal-sized cells). Chemotaxis mutants that always ran when they we re normal sized always ran when they were filament sized, and those mutants that always tumbled when they were normal sized always stopped when they w ere filament sized. Chemoreceptors in filaments were localized to regions b oth at the poles and at intervals along the filament. We suggest that the l ocation of the chemoreceptors enables the chemotactic responses observed in filaments. The implications of this work with regard to the cytoplasmic di ffusion of chemotaxis components in normal-sized and filamentous E. coli ar e discussed.