Architecture and Deposition of Cellulin Granules inApodachlyaSp.

Abstract

Cellulin, the unique chitin-glucan granules found in leptomitalean fungi, was investigated by cytochemical, interference contrast, ultraviolet fluorescence and electron microscopy. The concentric ring substructure, routinely observed by light microscopy observations of granules, was found to be present at the ultrastructural level. It was hypothesized that this concentricity was derived from alternating zones in which either chitin or 3-glucan was the predominant, but not necessarily exclusive, component. Electron microscopy demonstrated numerous cytoplasmic vesicles located on the granule perimeters or in close proximity. It was hypothesized that these vesicles deliver cellulin precursors and enzymes to the periphery of developing granules where the accretion of additional polysaccharide material occurs. No definitive observations were made demonstrating the nucleation of the granules.