Table 1.

Rotational biases and attractant responses of tethered cells expressing derivatives of Tar and Tap receptorsa

Plasmid gene-encoded construct% of time rotating CCW for unstimulated cellsAdaptation time (min) for attractant:
Strain VB13 (Δtar-tap Δtsr trg::Tn10)
 Tar854817  b
 Tap100NDc NDND
Strain MM509S (Δtar-tap tsr + trg +)
 Tarp4923 7.3
 Tart6321 6  
  • a Chimeric or otherwise engineered receptors are depicted in Fig. 1. Rotational biases, expressed as percentage of time rotating CCW, were measured manually from videotapes for 50 cells per strain and represent the behavior during a 30-s observation for each cell. Attractants were added to the flow chamber at 1 mM. Adaptation times were measured as the period of exclusively CCW flagellar rotation from 5 s after the onset of the attractant flow until the first reversal to CW flagellar rotation. The values given for adaptation times are the means for 40 cells per strain.

  • b —, no measurable response (because of inappropriate attractant for plasmid gene-encoded receptor).

  • c ND, not detectable (because cells were already turning their flagella exclusively CCW).