High concentrations of horse serum inhibit growth of corn stunt spiroplasma.

Corn stunt spiroplasma (CSS) grew faster and achieved higher titers in liquid or agar medium containing 5 or 10 percent horse serum than it did in medium containing 20 percent horse serum. When growth in liquid medium was initiated with a small inoculum, CSS achieved excellent growth in the presence of 5 percent serum but did not grow in medium containing 0 or 20 percent serum. Addition of arginine to liquid or agar medium supplemented with 20 percent serum stimulated CSS growth, but addition to that containing 5 percent serum did not.