Fig. 1. S. epidermidis strains isolated from normal human skin produce 6-HAP.

(A and B) Stability of antimicrobial molecules from S. epidermidis against GAS after heat-treatment for the indicated time (A) and incubation with indicated protease (B). The black area represents zone of growth inhibition of GAS. (C) Dose-dependent antimicrobial activity of the purified antimicrobial compound against GAS. Data are means ± SEM of three individual experiments. CFU, colony-forming unit. (D) ¹⁵N isotope incorporation into the antibiotic molecule after culturing S. epidermidis MO34 in tryptic soy broth (TSB) containing ammonium-¹⁵N chloride (12.5 mM). (E) The determined chemical structure of the active molecule, 6-HAP. (F) Capacity of 6-HAP to block in vitro DNA extension by Klenow fragment polymerase. A template that required adenosine (X = T) or cytidine (X = G) at the initial base for extension was used. (G) 5-Bromo-2′-deoxyuridine (BrdU) incorporation into tumor cell line, L5178, YAC-1 lymphoma, B16F10 melanoma, and Pam212 SCC after a 24-hour incubation in suitable media containing indicated concentrations of 6-HAP. Data are means ± SEM of four individual experiments. (H) BrdU incorporation into nontransformed human keratinocytes (NHEKs) and Pam212 cutaneous squamous cell carcinoma after 24-hour incubation in suitable media containing indicated concentrations of 6-HAP. Data are means ± SEM of four individual experiments.