The cell surface of Trypanosoma cruzi: a fracture-flip, replica-staining label-fracture survey

Fracture-flip and replica-staining label-fracture were used to study the nanoanatomy and topochemistry of the cell surface of Trypanosoma cruzi. Fracture-flip surface images differentiate the three main developmental stages of T. cruzi. Epimastigotes display a smooth surface, except the cytostome which appears as a clearly demarcated, raised, roughly textured platform. Amastigotes and trypomastigotes are covered by numerous surface particles with diameters ranging from 10 to 20 nm and 15 to 30 nm, respectively. Labeling of concanavalin A receptors showed that the surfaces of amastigotes and trypomastigotes were labeled, with amastigotes displaying the highest density of gold particles. In contrast, epimastigotes were sparsely labeled with exception of the cytostome, where a higher density of labeling coincided with the raised platform seen in fracture-flipped specimens, and with the particle-free area exposed on fracture faces. Labeling of epimastigotes by Ricinus communis I and Wistaria floribunda lectins showed that surface receptors for these lectins were absent from the cytostome.