Figure 1. Microbes and men. Locations of microflora are: skin (yellow): Propionibacterium acnes, Staphylococcus epidermidis; mouth (purple): Streptococcus salivarius, Streptococcus mutans; stomach (red): Helicobacter pylori; intestine (green): Bifidobacterium, Clostridium difficile, Escherichia coli, Eubacterium rectale, Bacteroides fragilis. (Diagram: Anne Kemmling, Goettingen, Germany.)

Figure 2. Diagram of the possible role of Propionibacterium acnes in the emergence of acne vulgaris. Top: an enlarged sebaceous gland. Bottom: possible interaction of P. acnes with surrounding tissue cells. Arrows pointing upward indicate that secreted enzymes degrade tissue, proteins, and fats, thereby providing nutrients to the bacteria. Downward arrows indicate inflammatory reactions caused by factors secreted by P. acnes. (Diagram: Holger Brueggemann, Goettingen, Germany.)