SURFACE-CHARGE AND SURFACE CARBOHYDRATES OF CRYPTOBIA-SALMOSITICA VIRULENT AND AVIRULENT FORMS AND OF CRYPTOBIA-BULLOCKI (KINETOPLASTIDA, CRYPTOBIIDAE)

The surface charge and surface carbohydrate residues of the virulent ( freshly isolated from the fish blood) and avirulent forms (from cultur e) of Cryptobia salmositica and one strain of C. bullocki were studied . Measurements of the zeta potential of parasites showed that C. bullo cki and the virulent form of C. salmositica had a net negative surface charge of about -15 mV, whereas the attenuated form of C. salmositica showed a surface charge of -7.9 mV. Enzymatic treatments of parasites with neuraminidase. trypsin. or phospholipase C indicated the presenc e of sialic acid residues, phosphate groups, and protein glycoconjugat es as components of the Cryptobia surface that accounted for their sur face charge. Residues of alpha-D-man, alpha- and beta-D-gal, alpha-D-g alNAc. alpha-L-fuc, and D-glcNAc could be detected on the surface of a ll parasites by specific fluorescein isothiocyanate (FITC)- and colloi dal gold-labeled lectins, The cell surface of the avirulent form of C. salmositica showed the strongest reactivity to almost all lectins tes ted. A remarkable binding pattern of lectins in the anterior region of parasites was observed.