Biochemical Evidence for the Exclusion of Zoophagus Insidians from the Oomycetes

Abstract

Pantonemic fungi possess plant-like metabolic features and are presumed to have evolved from algal ancestors. These fungi are unable to synthesize ergosterol and its precursors, and produce mycolaminaran rather than glycogen as a storage material. Zoophagus insidians is considered an exception in that it produces ergosterol. In CsCl gradients of cell extracts from Z. insidians, a white band atypical of pantonemic fungi which gives a positive iodine test for glycogen was observed. To verify this finding we subjected a true fungus {Coprinus), a pantonemic fungus {Phytophthora), and Zoophagus to glycogen and mycolaminaran isolation procedures. Spectrophotometric and infrared spectra confirmed the presence of glycogen and absence of mycolaminaran in Zoophagus. Based on these data, and the previously reported presence of sterols, we conclude Z. insidians is not a pantonemic fungus.