Figure 6. Visualization of Pol III* exchange in vivo.
(A) Left: image of τ (orange) and ε (blue) foci within a single E. coli cell, averaged over 40 s. Co-localization of the two signals is shown as a white spot. Middle: bright field image of the same cell. Right and below: fluorescence intensity of τ (orange) and ε (blue) over time. The trajectories are averaged using a 2 s moving average filter. (B) Averaged, normalized cross-correlation functions. The cross-correlation function of 1210 pairs of foci in living cells shows a clear positive peak (black line). The cross-correlation function for 297 pairs of foci in fixed cells (gray line) and the cross-correlation function of 1210 pairs of foci, randomized within the same field of view (red line) show no positive cross correlation. Cross-correlation functions have been vertically offset for clarity. (C) Exponential fit (red) to the cross-correlation function in (B). We obtained an exchange time scale of τ = 4 ± 2 s. The error represents the error of the fit.