Cyst and germ tube wall structure in Aphanomyces astaci, Oomycetes.

Aphanomyces astaci secondary cyst walls and walls of germinating spores were prepared by alkaline hydrolysis, autolysis, sonication, and enzymic degradation and were examined by shadow-casting and negative-staining techniques. The cyst wall consists of randomly oriented fibrils, about 3 nm in diameter. The fibrils are embedded in, or covered by, amorphous beta-1,3-glucans which can easily be removed by alkaline hydrolysis. The germ tube wall surface has the same structure, but the amorphous layer is less easily removed.