Figure 4. A theoretical model based on the absorption of peptides in E. coil cells.

(A) E. coli cells replicate with a rate of $k_D$ and they get killed with a rate of $k_k$ Each dead cell quickly absorbs $N$ AMPs. (B) Demonstration of the inoculum effect for the initial AMP concentration [LL37]=1.2 μM. A culture with high inoculum size ($3\times {10}^6$ cells/ml) survives as peptides deplete (solid lines) whereas growth in small inoculum size (${10}^6$ cells/ml) is inhibited with excess peptides remaining in the solution (dashed lines). Despite the survival of culture with high inoculum size, the growth is delayed. (C) Comparison of the MIC between the theoretical model and the experimental data. (D) Growth delay as a function of [LL37]. Solid lines are theoretical results (not a fit) and circles represent experimental data from microplate experiments (Figure 1). The delay is calculated with respect to the lowest AMP concentration (row H) of Figure 1AB.