Electron microscopy shows antibacterial effect. P. acnes bacteria were (A, B) left untreated or (C, D) incubated for one hour with chitosan, and then prepared for electron microscopy. Images were taken at 19,000x magnification with 1 μm scale bar (A, C) or 72,000x magnification with 250 nm scale bar (B, D). Figure 4A was modified by moving two parts of a larger image together. Images are representative of two separate experiments.