Table 3.
Flagellar rotational bias and swarming
| Strain | Reported/observed bias | Swarming |
|---|---|---|
| HCB429 | CCW (12) | − |
| HCB429/pJC3-AV413 | CCW (33) | − |
| HCB429/pPA56 | CCW/CW (22) | − |
| RP8611 | CCW (22) | − |
| RP8611/pMS103 | CCW/CW (23) | − |
| RP8611/pMS105 | CCW/CW (23) | − |
| RP437/pJC3-AV413 | CCW (33) | −/+ |
| RP2867 (cheBR) | CCW/CW (34) | − |
| RP9352 (MCP−cheZ) | CCW/CW (22) | − |
| RP437 | CCW/CW (13); | ++++ |
| RP4782 (fliM) | CCW (14); | ++ |
| RP4783 (fliM) | CCW (14); | + |
| SJW1103 | CCW/CW (18); | ++++ |
| MY107 (fliG) | CCW (18); | +++ |
| SJW2323 (fliG) | CW (18); | ++ |
| CCW↔CW |
The flagellar rotational bias of tethered cells (displayed in the histograms) was measured in the absence of chemotactic stimuli by observing 20 rotating cells for 60 sec each, as described in Methods. Cells were classified into five categories (from left to right): exclusively CCW, CCW biased with some reversals, frequent reversals with no bias, CW biased with some reversals, and exclusively CW. The height of the bars corresponds to the percentage of cells in each category. These rotational profiles were quite reproducible. The rotational bias of an E. coli cheA strain (RP9535) was CCW with cell distribution in each category (left to right) being 17, 1, 0, 0, 2; for an S. typhimurium cheA strain (KK2051; ref. 17) it was 17, 0, 0, 1, 2. These biases were very similar to those of the CCW switch mutants. Swarming ability in strains with plasmids was tested over a range (0–1,000 μM) of IPTG concentrations. Even without added IPTG, there is a basal level of gene expression. The negative results in strains with most plasmids were seen over the entire range of IPTG concentrations tested. In RP437/pJC3-AV413, the −/+ indicates either no swarming or 1-2 cm migration in different experiments with no added IPTG; swarming was completely blocked with even 10 μM IPTG. ++++, ≈8 cm; +++, ≈6 cm; ++, ≈4 cm; +, ≈2 cm after 16 h incubation.