Edwin C. White

Antibacterial Filtrates from Cultures of Aspergillus flavipes.

The production of a powerful, non-toxic antibacterial substance by Penicillium notatum has stimulated search in many quarters for other molds showing similar behavior. In addition to the work with Aspergillus flavus already reported, 1 the author has examined about 30 molds. Most of them were aspergilli, obtained from the collection of Dr. Charles Thorn. A number have shown antibacterial activity of varying degree, but one, Aspergillus fiavipes, has been of particular interest. As this work has been interrupted, it seems appropriate to record the results at this time. The mold was designated in the Thom collection “175.4303.46-Texas soil.”as received on an agar slant there was a heavy, tight mycelial growth which could be broken with difficulty, and spores for transfer were not easily obtained from this part of the growth. However, a light sandy area of sporulation was present at the tip of the slant where it was thinnest. This type of growth persisted in subcultures on slants, but by growing on Czapek-Dox agar in a petri dish an even, sandy growth with ample sporulation was obtained. The growth at room temperature is colorless for about 3 days, then takes on a light brown sandy appearance as sporulation develops, and after 4 or 5 days a characteristic camphor-like odor is noticed. This odor has been developed only on solid media. Little or no antibacterial activity was noted when the mold was grown on Czapek-Dox solution, but it appeared when a protein digest was used. With this medium (Tryptone-Difco) the best results were noted without any adjuvants at all, and sugar was definitely deleterious. The best medium of all, however, consisted solely of corn steep liquor, in the concentration of 5 or 10 ml to 100 ml of water.