Fig. 4. Chemotactic function of Tsr-F396 amino acid replacement mutants.
Chemotactic ability of cells carrying a mutant Tsr as their only chemoreceptor was evaluated by the size and morphology of their colonies on tryptone semi-solid agar plates after incubation for 8 hours at 30°C. Colony sizes were normalized to that of a wild-type Tsr control colony on the same plate. Mutant receptors with partial function (gray bars) produced colonies with a ring of chemotactic cells at their periphery, but with smaller diameters than the wild-type control.