ELABORATION OF ANTIBIOTICS BY BOLETUS LUTEUS AND CERTAIN OTHER MYCORRHIZAL FUNGI

Abstract

Several species of mycorrhizal fungi were examined for antibiotic formation when grown in laboratory media in the absence of the conifer seedling symbionts. Antibiotic activity was noted in filtered growth media and in acetone and chloroform extracts of mycelium. Acetone extracts of the mycelium of Boletus luteus were particularly active; the antibiotic was relatively stable and poorly water soluble. Its ultraviolet absorption spectrum exhibited absorption maxima at 223, 275, and 325 mμ. It was active against certain Gram-positive and Gram-negative bacteria but not against the yeasts, streptomycetes, or fungi which were tested.The chemical characteristics of this antibiotic and its presence in mycelium are features normally associated with polyene antibiotics. However, the known polyene antibiotics usually exhibit only antifungal activity.The elaboration of antibiotics by mycorrhizal fungi is discussed in terms of their possible significance in nature in the mycorrhizal association.