Electron microscopy of the rodlet layer of Neurospora crassa conidia

Neurospora crassa macroconidia possess a regularly arranged layer of small fibers (rodlets) near the spore surface. The structure and location of this layer were studied by making surface replicas, by negative staining, by freeze-fracturing and deep-etching, and by thin sectioning. When conidia were shaken vigorously in water, the layer fragmented and became separated from the surface in sheets. Negative staining of such sheets showed that the individual rodlets have a hollow central core. When conidia were shaken gently in water or fixative, large fragments of the rodlet layer often remained on the conidial surface. The fragments tended to fold back on each other such that multiple layers were sometimes seen in thin sections. It is concluded that in dry conidia the rodlets are located on the extreme outside of the spore where they form a monolayer with only occasional regions of overlap.