Abstract

It has been observed that a surface coat, 20 nm in thickness, extends from the plasma membrane of extracellular merozoites and that this coat contains strain-specific antigens. In the present study we determined the possible effect of protein in the culture medium on this structure. The surface coat on merozoites in culture medium devoid of protein was indistinguishable by transmission electron microscopy from the coat in a protein-containing medium. This supports the hypothesis that the surface coat originates from the parasite rather than from adsorbed serum protein.