Novel life cycle stages of Colpodella sp. (Apicomplexa) identified using Sam-Yellowe's trichrome stains and confocal and electron microscopy.

Colpodella spp. are free-living flagellates closely related to the apicomplexans. Human infections by Colpodella sp. have been reported. A biflagellated trophozoite and cyst stage comprise the known life cycle stages of Colpodella sp. However, the process of encystation and excystation within the life cycle is unclear. Life cycle stages initiating human infections are unknown. We performed a detailed investigation of the life cycle of Colpodella sp. (ATCC 50594) in culture using Sam-Yellowe's trichrome stains and differential interference contrast (DIC) for light microscopy and fluorescence microscopy of Congo red-stained cells and investigated ultrastructure using transmission electron microscopy (TEM). We report previously undocumented stages of Colpodella sp. Asymmetric and asynchronous division was detected inside cysts by trichrome staining and by TEM. Odd-numbered juveniles and cysts containing more than four juvenile trophozoites were identified. Live imaging of active cultures captured the excystation and egress of juvenile trophozoites and confirmed the presence of multinucleate cysts. The ultrastructure of the multinucleate cyst is reminiscent of apicomplexan schizonts. Insights gained from the life cycle stages observed in culture allowed the construction of the life cycle of Colpodella sp. Knowledge of the life cycle will aid biochemical and molecular characterization of Colpodella sp. and help identify stages in human infections.

Colpodella sp. (ATCC 50594) Life Cycle: Myzocytosis and Possible Links to the Origin of Intracellular Parasitism.

Colpodella species are free living bi-flagellated protists that prey on algae and bodonids in a process known as myzocytosis. Colpodella species are phylogenetically related to Apicomplexa. We investigated the life cycle of Colpodella sp. (ATCC 50594) to understand the timing, duration and the transition stages of Colpodella sp. (ATCC 50594). Sam-Yellowe's trichrome stains for light microscopy, confocal and differential interference contrast (DIC) microscopy was performed to identify cell morphology and determine cross reactivity of Plasmodium species and Toxoplasma gondii specific antibodies against Colpodella sp. (ATCC 50594) proteins. The ultrastructure of Colpodella sp. (ATCC 50594) was investigated by transmission electron microscopy (TEM). The duration of Colpodella sp. (ATCC 50594) life cycle is thirty-six hours. Colpodella sp. (ATCC 50594) were most active between 20-28 h. Myzocytosis is initiated by attachment of the Colpodella sp. (ATCC 50594) pseudo-conoid to the cell surface of Parabodo caudatus, followed by an expansion of microtubules at the attachment site and aspiration of the prey's cytoplasmic contents. A pre-cyst formed at the conclusion of feeding differentiates into a transient or resting cyst. Both DIC and TEM microscopy identified asynchronous and asymmetric mitosis in Colpodella sp. (ATCC 50594) cysts. Knowledge of the life cycle and stages of Colpodella sp. (ATCC 50594) will provide insights into the development of intracellular parasitism among the apicomplexa.