Microsporidian Spore Wall: Ultrastructural Findings on Encephalitozoon hellem Exospore

Publisher Website
Google Scholar
Abstract
A study of the spore wall of Encephalitozoon hellem was performed on thin sections, freeze‐fracture, and deep‐etched samples to obtain information on spore wall organization and composition. Our observations demonstrate that the spore wall is formed by an inner 30–35 nm electron‐lucent endospore and an outer 25–30 nm electron‐dense exospore. The exospore is a complex of three layers: an outer spiny layer, an electron‐lucent intermediate lamina and an inner fibrous layer. Freeze‐fracture and deep‐etching techniques reveal that the intermediate lamina and the inner fibrous layer result from the different spatial disposition of the same 4‐nm thick fibrils. In thin sections the endospore reveals a scattered electron‐dense material that appears in the form of trabecular structures when analyzed in deep‐etched samples. The presence of chitin in the exospore is discussed.