FIG 2.

Acne-associated strains respond to vitamin B₁₂ (VB12) supplementation and produce significantly more porphyrins. Strains from acne-associated P. acnes lineages (type I clades IA-2, IB-1, and IC) produced significantly more porphyrins when supplemented with vitamin B₁₂ (10 μg/ml) than did the controls. Strains from other lineages (type I clades IA-1, IB-2, and IB-3, type II, and type III) did not respond to vitamin B₁₂ supplementation in porphyrin production. Porphyrin production is defined as the concentration of porphyrins produced (in micromolar) normalized by bacterial growth measured as the OD₅₉₅. Each bar represents the average porphyrin production by one or more strains in the same lineage. The average and the SEM were calculated based on the data obtained from at least three independent experiments with at least four replicates each (*, P < 0.05).