TABLE 4.
Straina | Genotype | Switching frequency (10−3)
|
fljBOn to fljBOff/fljBOff to fljBOn | |
---|---|---|---|---|
fljBOn to fljBOff | fljBOff to fljBOn | |||
14028 | dam+ | 1.69 | 0.446 | 3.8 |
dam mutant | 2.79 | 0.820 | 3.4 | |
DamOP | 1.90 | 0.238 | 8.0 | |
LT2 | dam+ | 1.19 | 0.469 | 2.5 |
dam mutant | 2.23 | 0.463 | 4.8 | |
DamOP | 1.65 | 1.26 | 1.3 |
fljB::lacZ transition rates (per cell per generation) of fljBOn to fljBOff and fljBOff to fljBOn were calculated from a single blue colony (Lac+) or a single white colony (Lac−) from dam+, dam mutant, and DamOP derivatives of fljB5001::MudJ fusions (38) in Typhimurium pathogenic strain, 14028, and avirulent laboratory strain, LT2, grown on minimal E medium agar (25) containing 0.2% glycerol and 40 to 80 μg of X-Gal/ml. Colonies exhibiting a Lac+ or Lac− phenotype (no sectors) were excised from the agar and plated to determine the total number of organisms in the colony and to score the Lac phenotype after incubation for 48 h at 37°C. Transition rates represent the weighted average of five independent colonies as described in Materials and Methods.