Changes in cell surface anionogenic groups during differentiation ofHerpetomonas samuelpessoai mediated by dimethylsulfoxide

The surface anionic groups of untreated or dimethyl sulfoxide (DMSO)-treatedHerpetomonas samuelpessoai cells were analyzed by cell electrophoresis, ultrastructural cytochemistry, and identification of sialic acids using thin-layer chromatography. Differentiation ofH. samuelpessoai induced by DMSO treatment caused a significant increase in the net negative surface charge. In flagellates exposed to DMSO, more cationized ferritin, colloidal iron hydroxide, and sendai virus particles bound to the cell surface. Treatment of both untreated and DMSO-treated flagellates with neuraminidase decreased markedly the EPM of cells to the cathodic pole. These findings suggest that sialic acid residues are the major anionogenic groups exposed on the surface ofH. samuelpessoai. Thin-layer chromatography showed thatN-acetyl andN,O-diacylneuraminic acids, in equal proportions, were present inH. samuelpessoai. However,N-acetylneuraminic acid predominates in DMSO-treated cells.