Mycoplasma, " which is a genus of bacteria that lack a cell wall around their cell membrane. They are the smallest bacterial cells yet discovered, typically ranging from 0.2 to 0.3 micrometers in size. Mycoplasmas are parasitic and can cause various diseases in animals and humans, including respiratory infections, urinary tract infections, and sexually transmitted diseases. Mycoplasma species are known for their ability to colonize the respiratory and urogenital tracts of humans and animals. Some species are considered pathogenic, while others are commensal, meaning they can exist harmlessly in the body without causing disease.