Production of Fungal Arbuscular Organs on Laboratory Media

Abstract

INTEREST in the morphology of fungal assimilatory organs was aroused by the appearance of vesicles and arbuscles on hyphæ of Memnoniella echinata penetrating textile fibres during cellulolysis. Vesicles have been reported on hyphæ within a medium when they are grown under conditions of deficient aeration, increased ionization, physiological unbalance of temperature, humidity or nutrition, and especially after the addition of bacterial, fungal or plant metabolites. No arbuscles have been obtained by these means, probably because the conditions or concentrations necessary for their appearance suppress germination of spores and growth of the fungus. The temporary arbuscular development on certain mutant strains of Phytophthora cactorum described by Stamps¹ suggests lack of a biosynthetic intermediate concerned with cell-wall structure. Inhibition of normal metabolic pathways, accentuation of overflow intermediates, and the functioning of latent shunt reactions, probably underlie vesicular development under the conditions enumerated above. The transformation of Gram-negative bacilli into swollen spherical cells because of reduction in cell-wall content of muramic and diaminopimelic acids described by Salton and Shafa² as the effect of a fungal metabolic product, and by Brenner et al.³ as the result of lysozyme treatment, bacteriophage action, excess lysine, and deprival of diaminopimelic acid, together with the recent work of Eddy and Williamson⁴ on the development of irregularly shaped outgrowths on yeast protoplasts under the action of digestive juices, seem to be similar phenomena. In the experiments now to be described, I accept as a working hypothesis that vesicles and arbuscles are primarily a manifestation of fungitoxic factors, though an element of adaptation to nutritional requirements undoubtedly enters into their morphology.