Mycoplasma pneumoniae (Eaton agent) is an infectious agent that:

Mycoplasma pneumoniae is the causative agent of primary atypical pneumonia, which was initially described by Eaton, giving rise to the eponym Eaton agent. Mycoplasma pneumoniae requires sterols for growth, usually in the form of cholesterol that is incorporated into the cell membrane. Mycoplasma pneumoniae lacks muramic acid in its cell wall as do all micro-organisms belonging to genus Mycoplasma. Similarly, and in harmony with other species of the genus, Mycoplasma pneumoniae contains both DNA and RNA. Mycoplasma pneumoniae is completely resistant to Penicillin, which inhibits cell wall synthesis, because Mycoplasma pneumoniae does not have a cell wall. Mycoplasma may cause a hemolytic anemia (cold agglutination). Ref: Ray C.G., Ryan K.J. (2010). Chapter 38. Mycoplasma and Ureaplasma. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.