Mycoplasma spermatophilum is a species of bacteria in the genus Mycoplasma. This genus of bacteria lacks a cell wall around their cell membrane. Without a cell wall, they are unaffected by many common antibiotics such as penicillin or other beta-lactam antibiotics that target cell wall synthesis. Mycoplasma are the smallest bacterial cells yet discovered, can survive without oxygen and are typically about 0. 1 µm in diameter. The type strain is AH159 = ATCC 49695 = CIP 105549 = NCTC 11720.