Propionibacterium acnes is a tiny microbe that lives in the oily region of the skin's pores. The bacteria can aggravate an immune response which causes red, swollen bumps to develop on the skin (acne).
The researchers collected samples of P. acnes from the noses of 49 pimply people and 52 people with clear skin. They extracted the microbial DNA from the strips and tracked a genetic marker to identify the bacterial strains.
They sequenced the genomes of 66 different P. acnes strains, which allowed them to analyze the genes in each of the strains.