2-DE of P. acnes culture supernatants. Bacteria were grown in BHI medium to an OD600 of 0.6. Supernatants were harvested and precipitated. Protein samples (200 μg) from each strain were separated on 2-DE gels and visualized by staining with Coomassie Brilliant Blue G-250. The following strains were used: (a) KPA171202 (type IB); (b) P6 (type IB); (c) 266 (type IA); (d) 329 (type II); (e) 487 (type III). Information about the identified protein spots is provided in additional file 2.