The MMP ratio is correlated with lifespan and declines with age in WT cells. (A) Schematic of the two-component construct. (B) Representative composite fluorescent images taken from the YLM showing the expression of the reporter construct in the same mother cell when young (top) and old (bottom). Overlap of the MMP_s (green) and MMP_i (magenta) signals appears white. The full set of fluorescence images associated with this cell can be seen in Video 1. (C and D) Trajectories of the MMP ratio (MMP_s/MMP_i) as cells age. Each gray line represents the centered (i.e., mean-normalized) MMP ratio trajectory of a single cell. Trajectories are from cells that were observed to die in the device (n = 11,856 from 17 experiments). Uncentered trajectories can be found in Fig. S1. Black line indicates the mean trajectory. (C) Centered MMP ratio as a function of time. (D) Centered MMP ratio as a function of number of divisions. (E) Number of divisions achieved before cell death as a function of the MMP ratio when young (0–5 divisions). Data are from the same cells analyzed in C and D. r is the Pearson correlation coefficient, and p is the P-value of the estimate of r.