Structure of the cell wall of Pythium debaryanum.

The structure of hyphal walls of Pythium debaryanum was investigated by electron microscopy of shadowed replicas and thin sections, before and after digestion by snail gut enzymes or by 1 n HCl at 100 C for 1 hr, and by X-ray diffraction. We found that the wall had two phases, one composed of microfibrils of unknown composition and a second consisting of an amorphous matrix, part of which stained like protein with potassium permanganate and part of which was removed by snail-gut enzymes. In the microfibrillar phase, there were two layers; an outer, thicker layer of randomly disposed microfibrils and an inner, thin layer of microfibrils oriented parallel to the hyphal axis. As in Neurospora crassa, the amorphous phase included a branching system of pores, 40-80 A in diameter. Unlike N. crassa, the cytoplasm of Pythium showed Golgi bodies frequently, and many lomasomes were observed between the cytoplasmic membrane and the wall. The relations between these organelles and the mechanism of wall formation in Pythium are not understood.