TABLE 1.

Rotational biases and attractant responses of tethered cells expressing derivatives of Tar and Tap receptors^a

Plasmid gene-encoded construct	% of time rotating CCW for unstimulated cells	Adaptation time (min) for attractant:
		Asp	Maltose	Pro-Leu
Strain VB13 (Δtar-tap Δtsr trg::Tn10)
Tar	85	48	17	—b
Tap	100	NDc	ND	ND
Tarp	100	ND	ND	ND
Tapr	74	—	—	2.3
Tart	100	ND	ND	ND
Tapl	100	ND	ND	ND
Strain MM509S (Δtar-tap tsr+trg+)
Tap	62	—	—	0.5
Tarp	49	23	7.3	—
Tart	63	21	6	—
Tapl	71	—	—	0.6

^aChimeric 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). 

^cND, not detectable (because cells were already turning their flagella exclusively CCW).