Figure 4.

Rotation speeds after induction of the S gene or addition of DNP. (a) Cells of strain RY8797pQpS105_A52G were tethered to a glass coverslip, induced at t = 0, recorded, and analyzed for rotation speed, as described in Materials and Methods. The mean of the normalized rotation speeds for 10 individual cells at each time is plotted, except for the 25-min time point, where the value is for seven surviving cells. The vertical bars indicate one standard deviation. (b) RY8797 cells were tethered to glass slides, equilibrated with prewarmed TB medium, and exposed to a 5-min flow of prewarmed TB medium containing DNP at the indicated concentrations. The rotation speed of at least 20 individual cells was determined 5 min after the addition of DNP and normalized to the rotation speed determined before addition. The vertical bars indicate one standard deviation. (c) DNP-induced triggering of S. Cultures of strain RY8797pQpS105 were grown in TB medium at 37°C to an A550 = 0.2 and induced at t = 0 with IPTG and arabinose. At t = 20 min, DNP was added to a final concentration of 0 μM (●), 5 μM (○), 50 μM (■), 100 μM (□), 200 μM (▴), 400 μM (Δ), 600 μM (▾), 1,000 μM (×), and 1,500 μM (⧫). After DNP addition, the turbidity of the cultures was monitored as A550 until lysis was complete.