Propionibacterium acnes (p. Acnes) bacteria are classified into different types based on gene sequencing and biological characteristics and play a role in acne formation. P. acnes promotes comedones through biofilms, the IGF pathway, aberrant integrin expression, production of free fatty acids, and oxidation of squalene. P. acnes also interacts with toll-like receptors and forms biofilms that contribute to acne.