Single Cell Dynamics

Mario Feingold

We use single cell phase-contrast and fluorescence time-lapse microscopy to monitor the morphological changes during the division of E. coli. To bypass the limitations of optical resolution, we process the images using pixel intensity values for edge detection. We study the dynamics of the constriction width, W, and find that its formation starts shortly after birth much earlier than can be detected by simply viewing phase-contrast images. A simple geometrical model is shown to reproduce the behavior of W(t). Moreover, the time-dependence of the cell length, L(t), consists of three linear regimes. The growth rates in the different regimes are related to each other and to the parameters of our model.
 

Phase-contrast (right) and fluorescence (left- stained membrane) images of bacteria (E.coli).

This is life: 1.5 min (a), 8.6 min (b) and 19.4 min © from birth. In © the bacterium has just divided.

During the lifetime of a bacterium it elongates linearly in three regimes. The transition between these regimes is rather sharp. Click to enlarge.