Symbiote-free hemoflagellates, Blastocrithidia culicis and Crithidia oncopelti: their liver factor requirement and...

Several aposymbiotic strains of Blastocrithidia culicis and Crithidia oncopelti were cultivated in Trager's chemically defined medium as well as in a blood broth, both supplemented with 0.25% (v/v) liver extract concentrate. For all such strains, the liver extract was found to serve as an essential growth factor in the defined medium and as growth promoting additive in the blood broth. The active molecules were found to be water-soluble, heat stable, dialyzable, and probably nonlipid fractions. Antisera were developed in rabbit against all the available aposymbiotic strains. An almost total cross-reactivity at very high titers was observed in reciprocal agglutination test using strains with and without the bacterial symbiotes. These results indicate that the loss of the symbiotes does not affect the antigenic identity of B. culicis and C. oncopelti.