"Tetracycline (INN) (
/ˌtɛtrəˈsaɪkliːn/) is a broad-spectrum polyketide antibiotic produced by the 
Streptomyces genus of Actinobacteria, indicated for use against many bacterial infections. It is a protein synthesis inhibitor. It is commonly used to treat acne today, and, more recently, rosacea, and is historically important in reducing the number of deaths from cholera. Tetracycline is marketed under the brand names Sumycin, Tetracyn, and Panmycin, among others. Actisite is a thread-like fiber formulation used in dental applications. It is also used to produce several semisynthetic derivatives, which together are known as the tetracycline antibiotics. The term "tetracycline" is also used to denote the 4-ring system of this compound; "tetracyclines" are related substances that contain the same 4-ring system."