Mycoplasmas differ from chlamydiae in that they are: (A) Susceptible to penicillin, (B) Able to grow on artificial cell-free media, (C) Able to cause urinary tract infection, (D) Able to stain well with Gram's stain
Answer is B. Mycoplasmas lack a rigid cell wall and are bound by a triple-layer unit membrane. For this reason, they are completely resistant to the action of penicillins. Unlike the chlamydiae, they can replicate in cell-free media.