Final answer:
The causative agent of Lyme disease in North America is Borrelia burgdorferi, a Gram-negative spirochete bacterium transmitted by black-legged ticks.
Step-by-step explanation:
The causative agent of Lyme disease in North America is Borrelia burgdorferi. This is a Gram-negative spirochete bacterium that is transmitted to humans through the bite of infected ticks.
Specifically, the black-legged tick or deer tick, Ixodes scapularis, is responsible for transmitting Lyme disease in the northeast, mid-Atlantic, and north-central U.S., while on the Pacific coast, it is transmitted by the western black-legged tick, Ixodes pacificus.
Lyme disease is characterized by symptoms such as a bullseye rash, and if left untreated, it can cause chronic disorders in the nervous system, eyes, joints, and heart. Lyme disease is the most common vector-borne disease in the United States and is a significant health concern due to the expanding range of the tick species that transmit it.