Cryo-enhancement of ultrastructural, immunological, cytochemical, and low-voltage SEM characterization of fungal growth and morphogenesis

Abstract

Cells of filamentous fungi exhibit a characteristic somatic form, organized as a linear file of individual cells, known as the hypha. Growth of the fungus occurs primarily through expansion at the apex of the hyphal tip cell, where highly organized and localized exocytosis is thought to be responsible for the deposition of new cell wall. In pathogenic fungi, changes in the pattern of tip growth are the means by which specialized infection structures develop, enabling the fungus to adhere to and penetrate the host surface, establish infection and cause disease. The use of cryo techniques has provided a vastly expanded knowledge of the cellular bases underlying these important morphogenetic events.Hyphae are easily grown as a monolayer in culture, on pieces of cellophane overlying nutrient agar. These cell monolayers are easily manipulated for plunge freezing with minimal perturbation and no treatment necessary prior to quenching. In this sense, plunge freezing is superior to other cryo-fixation techniques that require pre-treatment or mounting of live specimens onto holders, hats or pistons.