The microbiome of humans consists of different microorganisms that both live inside and outside the body, in which the skin, the oral mucosa, and the gastrointestinal tracts are the most common h abitat for the complex microbial community. Each individual has different microbiome composition and form s a symbiotic association with them. Take the skin microbiome as an example, it's made up of diverse organisms such as different strains of bacteria, viruses, and fungi, and usually, they live in a state of balance. But when alterations occur, the skin microbiome may lead to some skin diseases, such as acne vulgaris . Acne vulgaris is one of the most common inflammatory skin conditions , which is related to a gram-positive bacterium, Cutibacterium acnes (C. acnes) . C. acnes is the most abundant skin commensal of the human skin microbiome and has different strains, some of which predominate in healthy skin and others are associated with acne. Healthy skin means dif...