Effect of various enzyme treatments against the heat–killed <i>C</i>. <i>acnes</i> cells on their ability to induce melanization of the silkworm hemolymph.

(A) Preparation of the enzyme–treated C. acnes (AC) fraction (C. acnes [Ac–En]). The C. acnes (AC) fraction was treated with DNase, RNase A, and protease K. (B, C) Silkworms were injected with 50 μl of saline (Saline), the autoclaved C. acnes cell suspension (C. acnes [AC]), or the enzyme–treated C. acnes (AC) fraction (C. acnes [Ac–En]). After incubation for 3 h at 37˚C, the silkworm hemolymph was collected. Photographs of the silkworm hemolymph were taken (B), and absorbance at 490 nm (A490) (C) was measured. The arbitrary unit was defined as the absorbance at 490 nm of a sample of silkworm hemolymph (50 μl) mixed with saline (50 μl). n = 5–7/group. Statistically significant differences between groups were evaluated using the Tukey–Kramer test. *P < 0.05.