SOME PROPERTIES OF A BACTERIAL-INHIBITORY SUBSTANCE PRODUCED BY A MOLD'

In 1929, Fleming observed that a mold which he identified as Penicillium rubrum (Biourge), but which more closely resembles Penicillium notatum (Westling) and belongs to the group of which Penicillium chrysogenum is the type species, (Thom, 1930) was able to produce a substance which inhibited the growth of certain bacteria. During 1930 a large number of molds2 were studied in this laboratory in an attempt to find others than the one isolated by Fleming which would produce a similar inhibitory substance. Since none were found, the following experiments were conducted on the filtrate from Fleming's culture when grown on veal infusion broth or on a modified Czapek-Dox synthetic medium having the composition described by Clutterbuck, Lovell and Raistrick (1932) with the hope of gaiing some information with regard to the nature of the inhibitory substance. The mold was permitted to grow at 20'C. for a period varying from seven to ten days on veal medium or twenty to twenty-five days on the synthetic medium. After the growth period, th