Occurrence of a Resistant Biopolymer in the Outer Walls of the Parasitic Algaprototheca Wickerhamii(chlorococcalses): Ultrastructural and Chemical Studies¹

The occurrence of a resistant biopolymer termed PRP (Polymère Résistant de Prototheca), was demonstrated in the trilaminar outer walls (TLS) of Prototheca wickerhammi Soneda and Tubaki. PRP is located in the two electron‐dense zones of the TLS and accounts for ca. 0.3% of the total algal biomass. Several features of PRP (resistance to non‐oxidative treatments, insolubility in dioxane, mode of deposition, UV fluorescence) were previously observed both in sporopollenins and in the resistant biopolymer of Botryococcus braunii outer walls. However elemental composistion and IR spectra revealed very important structural defferences between the latter material and PRP. Similar elemental compositions, but substantial differences in IR spectra, were noted between PRP and classical sporopollenins. PRP is proabaly derived from the polymerization of terpenic units; but, taking into account the spectroscopic oservations, these monomeric units are not carotenoids. The presence of PRP in the outer walls of P. wickerhamii may be related to the drug and lysosome resistance of this parasitic species.