Table 1.
Swarming rates in soft agar of fliG motA double mutants, measured relative to wild-type controls on the same plates
| FliG mutation | MotA mutation
|
||||||
|---|---|---|---|---|---|---|---|
| WT | R90A | E98Q | E150Q | R90E | E98K | E150K | |
| WT | 1.00 | 0.71 | 0.98 | 1.09 | 0.00 | 0.00 | 0.66 |
| E224A | 1.02 | 0.69 | 0.86 | 1.07 | 0.00 | 0.00 | 0.56 |
| E237A | 1.12 | 0.73 | 0.94 | 1.14 | 0.00 | 0.00 | 0.58 |
| K264A | 0.96 | 0.09 | 0.66 | 1.03 | 0.00 | 0.00 | 0.45 |
| K264E | 0.69 | 0.00 | 0.00 | 0.66 | 0.00 | 0.00 | 0.00 |
| E272A | 1.01 | 0.71 | 0.81 | 1.04 | 0.00 | 0.00 | 0.70 |
| R281A | 0.86* | 0.00 | 0.53 | 0.91 | 0.00 | 0.00 | 0.00 |
| R281D | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
| R281V | 0.04 | NM | NM | NM | NM | 0.29 | NM |
| R281W | 0.12 | NM | NM | NM | NM | 0.18 | NM |
| R287A | 1.02 | 0.59 | 0.85 | 1.06 | 0.00 | 0.00 | 0.64 |
| D288A | 0.94 | 0.10 | 0.15 | 0.97 | 0.00 | 0.00 | 0.00 |
| D289A | 0.92 | 0.72 | 0.00 | 0.91 | 0.40 | 0.00 | 0.00 |
| D289K | 0.23 | 0.58 | 0.00 | 0.15 | 0.77 | 0.00 | 0.00 |
| R297A | 1.10 | 0.11 | 0.66 | 1.03 | 0.00 | 0.00 | 0.09 |
| R297D | 0.27 | 0.00 | 0.00 | 0.34 | 0.00 | 0.00 | 0.00 |
| E302A | 0.96 | 0.34 | 0.61 | 1.00 | 0.00 | 0.00 | 0.44 |
| R313A | 1.00 | 0.54 | 0.81 | 0.84 | 0.00 | 0.00 | 0.68 |
| E320A | 1.06 | 0.72 | 0.85 | 1.14 | 0.00 | 0.00 | 0.78 |
| E327A | 0.96 | 0.40 | 0.75 | 0.95 | 0.00 | 0.00 | 0.43 |
| D328A | 1.12 | 0.41 | 0.92 | 1.07 | 0.00 | 0.00 | 0.35 |
Values are the mean of two determinations that differed by an average of 6%. The mutant FliG and MotA proteins were expressed from plasmids in the fliG motA double-mutant strain DFB245. The wild-type (WT) control was the fliG motA double-mutant strain expressing wild-type FliG and MotA from the plasmids; its swarm rate was 7.5 mm/hr. Instances of synergism are indicated by boldface type, and instances of suppression are indicated by boldface italic type. NM, not measured.
The FliG mutant R281A swarmed at only 40% of wild type in a previous mutational study of fliG (26) but faster in the present study. This difference is due to different levels of MotA in the two experiments. In the previous study, MotA was expressed from the chromosome, whereas in the present study MotA was moderately overexpressed from a plasmid. When a plasmid expressing wild-type MotA (pJZ19) was introduced into the strain used in the previous study, the swarming rate of the R281A mutant increased to about 90% of wild type.