FIGURE 1.

Partitioning of a fluorescent protein during microcolony growth. (A) Snapshots from a typical dilution experiment. Images are taken using yellow fluorescence filters, and the time between the frames shown is ∼36 min. (B) The lineage tree extracted from the same movie. Time increases downwards as more and more divisions occur. Measurements are marked by a dot and were taken approximately every 9 min (giving a total of just over 700). (C) Cellular fluorescence only decreases significantly at cell division. For this dataset, fluorescence measurements were taken every second frame, i.e., every 18 min. The first cell divides after ∼20 min, and its daughters in turn both divide at 60 min. Notice the different fluorescence values in each daughter cell become more apparent at later divisions. For clarity, only the initial part of the movie is shown. (D) Schematic of a lineage tree generated from an initial cell with fluorescence value f₁. Second-generation cells have fluorescence f₂ or f₃, while third-generation cells have f₄, f₅, f₆, or f₇.