Steroid Growth Requirements and Steroid Growth Inhibitors of Mycoplasma

SUMMARY: Mycoplasma laidlawii strain A did not grow significantly and sometimes died in a peptone + yeast extract (PY) medium; good growth was obtained when 1 yo serum or 1 yo bovine plasma albumin was added. The addition of cholesterol and some other steroids (at 20pg./ml.) to the basal PY medium gave some growth although less than that given by adding serum or albumin. Certain other steroids (e.g. A1v4 and A1 9 *6-cholesten-3-one) were potent inhibitors of cholesterol-promoted growth at one-tenth the cholesterol concentration. One of these steroids at 2pg./ml. inhibited the growth which was obtained in PY + albumin medium; this inhibition was annulled by 200pg. cholesterol/ml. Two of the inhibitory steroids at c. 300pg./ml. inhibited the growth of M. laidlawii strains A and B, M. mycoides var. Capri and M. bowigenitalium in a rich serum-containing medium. The inhibitory effects of one of these steroids was greatly diminished when it was added after growth had begun. Cholesterol or related steroids have been found to be required for the growth of parasitic Mycoplamnu sp. (Edward & Fitzgerald, 1951; Smith, Lecce &amp