Harmful bacteria, a subset of the large domain of prokaryotic microorganisms known as bacteria, pose threats to human health by causing various infections and diseases. These pathogenic bacteria, which can inhabit various environments including soil, water, and the human body itself, are responsible for illnesses ranging from cholera and syphilis to anthrax and bubonic plague. Despite the fact that most bacteria are harmless and some even beneficial, the pathogenic variety can result in serious health issues if not properly dealt with. Antibiotics are typically used to treat such bacterial infections. However, the growing problem of antibiotic resistance is making treatment more challenging. Understanding and studying harmful bacteria, part of the field of bacteriology, is crucial for disease control and the development of effective treatments.