Cutibacterium acnes
Plain-English definitions of microbiome research vocabulary — the terms you'll see across articles, testing services, and probiotic claims.
The dominant bacterium on the human face (formerly classified as Propionibacterium acnes). It metabolises sebum and helps maintain the skin's acid mantle. Certain strains are associated with acne vulgaris, while others are found on healthy skin — the issue is strain imbalance rather than the species itself.
Related terms
Staphylococcus epidermidis
One of the most abundant commensal bacteria on human skin. S. epidermidis produces antimicrobial peptides that inhibit pathogenic bacteria including S. aureus, communicates with the immune system, and helps maintain the skin's acidic pH. Often called the "good staph."
Dysbiosis
An imbalance in the composition or function of the microbiome, typically characterised by reduced diversity, loss of beneficial bacteria, or overgrowth of potentially harmful species.