[Behavior of Mycoplasma strains in media with L-cystine]

Mycoplasma strains of all origins and species can grow on PPLO agar (pleuropneumonia-like organisms), if thallium and L-cystine are added. Brown-black is the coloration of the growing colonies, with the intensity of blackening varying by colony age. Blackening of the mycoplasma colonies is likely to facilitate germ counting, cloning, and evaluation of the growth inhibition test.