Mutual Antagonism between Pathogenic Fungi. Inhibition of Dimorphism in Candida albicans

Abstract

In 2 -membered pure cultures the pathogenic fungi, Trichophyton rubrum and Candida albicans, exert antagonistic effects on one another in vitro (1) inhibition of growth (marked inhibition of T. rubrum by a heat-labile metabolic product of Candida), (2) production of a yellow-brown color by T. rubrum in the 2-membered cultures as a result of acid production by Candida (the pigment of T. rubrum is a pH indicator), (3) complete inhibition of mycelial production by C. albicans. Two metabolic products of T. rubrum inhibit the yeast to mycelial conversion (Y->M): (1) soluble in water and in acetone, heat stable, adsorbed by Norite and eluted from it by dilute aqueous acid alcohol, (2) soluble in water, insoluble in acetone, heat labile, not adsorbed by norite. Conversion of Y->M was independent of pH (4.5-8), but was inhibited regularly by high concn. of NH4Cl (3%). It was concluded that the active fractions of T. rubrum filtrates were not the H+ or NH+4 ions. The general phenomenon of inhibition of cell division without simultaneous inhibition of growth, resulting in production of elongated cells is discussed in some detail. The possibility of inhibition or inactivation of a single enzyme complex responsible for cell division is briefly considered.