A highly sensitive and linear CoolSnap camera was used to record the fluorescence images of holdfasts, controlled by MetaMorph (Universal Imaging, PA) software. The attached cells were first brought into focus under phase contrast setting for easy location of the cells. Then the holdfasts were observed under fluorescence mode with fine adjustment of focus. Consecutive fluorescence images were taken with 0.1 s exposure time while manually adjusting the focus with the fine adjustment knob. Optimal focus was achieved within

ten attempts. The image of the 10th exposure was used to Y-27632 solubility dmso obtain the fluorescence intensities of holdfasts. Measurement of fluorescence intensity To measure the integrated fluorescence intensity, a circle larger than the holdfast image was drawn using the imaging software and the intensity was integrated over all the pixels inside the circle. The sum was then DUB inhibitor subtracted by the integrated background intensity of a nearby circle of the same size to obtain the integrated intensity of the holdfast. This method eliminates background intensity from the camera noise and from dye molecules adsorbed on the glass surface. The net integrated fluorescence intensity of holdfasts was measured for over 500 cells older than 7.5 min in age per time point. The fluorescence images of most holdfasts were sufficiently bright and their intensities were measured by an

automated routine using the commercial software Matlab (ATM/ATR inhibitor cancer Mathworks, Natick, MA, USA). A small sub-population of holdfasts were too dim to be recognized by the Matlab program and their intensities were determined

individually by the integrated intensity function in MetaMorph. For cells younger than 6.5 min, fluorescence intensities of almost all holdfasts were too weak to be recognized by the Matlab program. Instead, about 100 holdfasts at each chosen age were measured individually using MetaMorph. Selection of experimental condition for quantitative fluorescence analysis We used the following method to determine Dynein proper fluorescein-WGA labeling conditions. Synchronized swarmer cells were allowed to quickly attach to a glass microscope coverslip. The unattached cells were washed away. The attached cells were incubated for 27.5 min at 30°C to ensure formation of holdfasts. We then measured average intensity of those holdfasts labeled with 20, 100, and 500 μg/ml fluorescein-WGA for 15 min and average intensity of holdfasts labeled with 100 μg/ml fluorescein-WGA for 5, 10, 15 and 20 min in order to determine the dependence of the average integrated fluorescence intensity on dye concentration and incubation time. We found that the integrated fluorescence intensity was not sensitive to the lectin concentration or labeling time within these ranges, suggesting saturation of dye labeling under these experimental conditions.