Surface Anionic Groups in Symbiote‐Bearing and Symbiote‐Free Strains ofCrithidia deanei¹

The surface anionic groups of symbiote‐bearing and symbiote‐free strains of Crithidia deanei were compared by determining cellular electrophoretic mobility, by ultrastructural cytochemistry, and by identification of sialic acids by thin‐layer and gasliquid chromatography. Symbiote‐free Crithidia deanei has a highly negative surface charge (‐0.9984 μmċs ‐1 ċ V ‐1 ċ cm), which is slightly reduced (‐0.8527 μmċs ‐1 ċ V ‐1 ċ cm) by the presence of the endosymbiote. Treatment of both strains of C. deanei with neuraminidase decreased significantly the electrophoretic mobility of cells toward the cathodic pole, indicating the existence of exposed sialic acid residues responsible for the negative charge on the protozoan cell surface. Thin‐layer and gas‐liquid chromatography showed that N ‐glycolyl‐ and N ‐acetylneuraminic acids were present in both strains of C. deanei .