Figure 6. The σ^V circuit has a memory of previous stress.

Stress is removed from an activated system at time 0 and reapplied at a time indicated by the dashed line, lysozyme concentrations are indicated by the purple traces above time course plots.

• A
  Simulations predict that after a break in stress, on reapplication of stress all cells turn on σ^V immediately and homogeneously (N = 99).
• B, C
  With increasing intervals between stresses, response heterogeneity reappears in the model, indicating a loss of memory. (C) Each line represents the cumulative fraction of cells (N = 99) with σ^V concentration values that are higher than the half maximum of their final values (representing cells that have activated). If the interval between stress is increased long enough, (800 au), the heterogeneity is the same as if the cells had not experienced a prior lysozyme stress (control).
• D
  Experiments confirm memory in the σ^V circuit. For short intervals between stress applications, cells respond immediately and homogeneously. Each line corresponds to one of 48 single‐cell traces.
• E, F
  For very long intervals between stress (12 h), the heterogeneity is the same as if the cells had not experienced a prior lysozyme stress (control). N > 50 single‐cell traces.

Data information: For more information on the number of repeats, please see Appendix Table S3.