(A) Representative trajectory of a LacI-CFP-labeled groESL locus tracked in live CJW2966 cells showing the dynamics of a chromosomal locus. The DNA locus was imaged every 2 s for 180 s. The displacements were colored as a function of time and overlaid with the cell outline (green). The zoomed trajectory in the inset shows the magnitude of displacements. To induce LacI-CFP expression, cells were incubated for 1 hr with 0.03% xylose prior to imaging. (B) Left, two-dimensional distribution of the groESL locus positions relative to the mean position of each trajectory. The scatter plots were generated from locus positions of 641 trajectories while the mesh surface is the best 2-D asymmetrical Gaussian fit (with σlong = 0.06 µm and σshort = 0.04 µm). The lower plane is a heatmap of the experimental data. Right, the same data set is represented as 1-D distributions of the groESL locus positions relative to the mean position of each trajectory along the long and short cell axes in single cells. Experimental data (filled circles, long axis; open circles, short axis) and Gaussian fits (solid line, long axis; dashed line, short axis) are shown. (C) 1-D distributions of the 139_lac and 165_lac locus positions (Viollier et al., 2004) relative to the mean position of each trajectory along the long and short cell axes in single cells. Left, asymmetrical Gaussian fit gives σlong = 0.06 µm and σshort = 0.03 µm for the 139_lac locus in which the lac operators are inserted at position 1599540 on the C. crescentus chromosome (CJW5466 strain). Right, asymmetrical Gaussian fit gives σlong = 0.05 µm and σshort = 0.03 µm for the 165_lac locus in which the lac operators are inserted at position 2481399 on the C. crescentus chromosome (CJW5468 strain).