title: Ultrastructural and biochemical analysis of the relationship of Crithidia deanei with its endosymbiont.
abstract: Some protozoa of the Trypanosomatidae family harbor in their cytoplasm bacterial endosymbionts that provide essential nutrients to and induce morphological alterations in the protozoa. In the present study, a close association between endosymbionts and glycosomes, a peroxisome-like organelle where most of the enzymes of the glycolytic pathway are compartmentalized, was identified by conventional transmission electron microscopy in Crithidia deanei. Such an association was further supported by the cytochemical localization of catalase in the glycosome and also confirmed by 3-D reconstruction of the protozoan. The enzymes cytochrome oxidase and succinate dehydrogenase were detected by ultrastructural cytochemistry. A positive reaction was observed in the protozoan mitochondrion but not in the endosymbiont envelope. Enzymatic assays for succinate cytochrome c reductase reinforced these results, as a low enzymatic activity was detected in an endosymbiont-enriched fraction, while high activity was observed in a purified protozoan mitochondrion fraction. We also demonstrated that a purified symbiont fraction was able to hydrolyze ATP. This activity was Mg+2 dependent, since it was highly stimulated by the presence of physiological concentrations of this ion. Taken together, these observations suggest that no electron transporting system is active in the symbionts of Crithidia deanei and that they might obtain energetic molecules derivated from the protozoan glycosomes.
authors.affiliation: Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, RJ, Brazil.
authors.forename: M C
authors.initials: MC
authors.lastname: Motta
authors.forename: M J
authors.initials: MJ
authors.lastname: Soares
authors.forename: M
authors.initials: M
authors.lastname: Attias
authors.forename: J
authors.initials: J
authors.lastname: Morgado
authors.forename: A P
authors.initials: AP
authors.lastname: Lemos
authors.forename: J
authors.initials: J
authors.lastname: Saad-Nehme
authors.forename: J R
authors.initials: JR
authors.lastname: Meyer-Fernandes
authors.forename: W
authors.initials: W
authors.lastname: De Souza
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D003421:Crithidia / Q000201:enzymology* / Q000648:ultrastructure*; D003576:Electron Transport Complex IV / Q000378:metabolism*; D006019:Glycolysis; D008928:Mitochondria / Q000648:ultrastructure; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D013384:Succinate Cytochrome c Oxidoreductase / Q000378:metabolism; D013385:Succinate Dehydrogenase / Q000378:metabolism*; D013559:Symbiosis / Q000502:physiology*
chemical_list: D013384:Succinate Cytochrome c Oxidoreductase; D013385:Succinate Dehydrogenase; D003576:Electron Transport Complex IV; D010744:Phosphoric Monoester Hydrolases; D000251:Adenosine Triphosphatases