Francisella tularensis is a small, gram-negative bacterium that causes the infectious disease known as tularemia. It is highly infectious and can be transmitted to humans through contact with infected animals, bites from infected insects, or inhalation of contaminated aerosols. Symptoms of tularemia can include fever, skin ulcers, and swollen lymph nodes. This bacterium is found in various environments, particularly in areas where wildlife, such as rabbits and rodents, are present. Francisella tularensis is classified into different subspecies, with F. tularensis subsp. tularensis being the most virulent. Prompt diagnosis and treatment with antibiotics are essential for managing the infection effectively.