Phylogenetic trees of phages from P. acnes. A gene encoding a putative major head protein and a gene encoding a putative amidase were sequenced in nine P. acnes phages and aligned using MacVector ClustalW alignment. Phylogenetic trees were constructed using neighbor joining with best tree mode. The putative major head protein (A) was similar between all P. acnes phages examined and showed the highest similarity to Mycobacterium phage Che9d gp7, but did also have high similarity to Lactococcus phage phiLC3 MHP and Streptococcus phage SM1 gp40. If outgroups were removed (B) four separate groups of major head proteins could be observed. One group with PA6, another with PAS2 and PAS50, a third group with PAD21 and a forth group with PAS10, PAS12, PAS40, PAD9, PAD20 and PAD42. The putative amidase (C) showed similar patterning among the phages with phages PAS2 and PAS50 representing one group closely related to PA6, while the other phages PAS10, PAS12, PAS40, PAD9, PAD20, PAD21 and PAD42 formed a second group. The closest known phage protein with similarity to the putative amidase is represented by Mycobacterium phage PG1 gp49, but more related is P. acnes own amidase.