Antifungal Properties of Antibiotic Substances

Abstract

INTRODUCTORY Fungi, especially the filamentous types, have become definitely established as the most important group of organisms that is capable of producing antibac-terial substances under proper conditions of culture. No less significant, even if less well known, is the fact that many microorganisms, including fungi on the one hand, and bacteria and actinomycetes on the other, are capable of producing agents which possess antifungal properties. Some of the antibiotic substances which are active against bacteria are also characterized by fungistatic and fungicidal activities; others, however, may be active upon bacteria but not upon fungi. These facts have long been known to the plant pathologists, who were impressed by the ability of fungi to live in close association with other microorganisms in natural substrates, especially in the soil. Many of the organisms antagonistic to fungi were known to have a specific capacity of inhibiting the growth of various plant-pathogenic fungi and even of causing their destruction. This effect is selective and varies for different fungi, some being affected greatly and others slightly or not at all. The practical utilization of this phenomenon for the control of plant diseases has, therefore, been suggested (Chudiakov, 1935; Novogrudsky, 1936) and has actually been utilized on a limited scale. However, the ability of antagonistic microorganisms to attack fungi causing animal diseases (Chambers and Weidman, 1928) and the utilization of the antibiotic substances produced by these organisms for the purpose of combating such pathogens have received only cursory consideration (Waksman, 1945). The favorable effects that resulted from the practical utilization of certain antibiotic substances, such as tyrothricin, penicillin, and streptomycin, for the control of various human and animal diseases caused by bacteria suggested the possibility that some of these agents may also be utilized for the control of human and animal diseases caused by fungi. No attempt will be made to review here the very extensive literature on the antagonistic effects of various microorganisms upon fungi (Waksman, 1941). Studies of these reactions have resulted in the isolation of crystalline gliotoxin (Weindling, 1934) and in the demonstration that various bacteria produce antifungal agents (Chudiakov, 1935; Cordon and Haenseler, 1939). The effect of antibiotic substances upon fungi resulted in a modification of the morphology of the organisms, a change in some physiological mechanism such