Fluorescent Nanoparticle Uptake by Myzocytosis and Endocytosis in sp. ATCC 50594.

sp. (ATCC 50594) is a free-living biflagellate predator closely related to pathogenic Apicomplexa such as , and . sp. (ATCC 50594) obtain nutrients by preying on using myzocytosis. The organization of the myzocytic apparatus and the mechanism of nutrient uptake into the posterior food vacuole of species is unknown. In this study, we investigated myzocytosis using light and transmission electron microscopy. We investigated the uptake of 40 nm and 100 nm fluorescent nanoparticles and BioParticles by sp. (ATCC 50594) in a diprotist culture. Transmission electron microscopy was used to investigate the morphology of the tubular tether formed during myzocytosis. BioParticles were taken up by but not by sp. (ATCC 50594). Both protists took up the 100 nm and 40 nm beads, which were observed distributed in the cytoplasm of free unattached sp. (ATCC 50594) trophozoites, and also in feeding sp. (ATCC 50594) trophozoites and in the pre-cysts. Fragments of the nucleus and kinetoplast of and the nanoparticles were identified in the tubular tether being aspirated into the posterior food vacuole of sp. (ATCC 50594). Unattached sp. (ATCC 50594) endocytose nutrients from the culture medium independently from myzocytosis. The mechanisms of myzocytosis and endocytosis among species may provide important insights into nutrient uptake among the pathogenic apicomplexans.