FIG. 1.

Relationship of Aer function to Aer expression level. Measurements were made with the transducerless strain UU1250 carrying pKG106. Aerotactic ability was assessed on tryptone soft agar containing 50 μg/ml ampicillin and various IPTG concentrations. Fresh transformants were toothpicked to soft agar, and colony diameters (filled circles) were measured after incubation at 30°C for 17 h. Data points represent the mean values for four colonies; standard errors (not shown) were smaller than the size of the data symbol. The dashed line indicates the size of UU1250 colonies carrying a control vector (pNP1). Aer expression levels were determined in tryptone cell cultures grown to mid-log phase at 30°C as described in Materials and Methods. Aer expression levels in pKG106/UU1250 were normalized to that for RP437 (wild type) measured in parallel.