Date of Award

Winter 1-1-2020

Degree Type

Thesis

Degree Name

Master of Science In Biology Degree

Department

Biological, Geological and Environmental Sciences

First Advisor

Sam-yellowe, Tobili Y.

Second Advisor

Girish C. Shukla

Third Advisor

B. Michael Walton

Abstract

Colpodella species are free living biflagellated protists that prey on algae and bodonids in a process known as myzocytosis. Colpodella are phylogenetically closely related to Apicomplexa. Cyst and trophozoite stages have been identified in Colpodella species, however the mechanisms of encystation and excystation are unknown. The timing and transition of the life cycle stages are unknown. In the present study I investigated the life cycle of Colpodella sp. (ATCC 50594). Colpodella sp. were grown in diprotist cultures in tissue culture flasks containing Hay medium bacterized with Enterobacter aerogenes and containing Bodo caudatus as prey. I wanted to know the timing and duration of the life cycle and the transition stages of Colpodella sp. Time course experiments were performed to determine the duration of the life cycle stages, to investigate the transition of stages within the life cycle, and to identify the predominant cyst stage in resting cultures. The first four time courses were performed to identify the active stage of the life cycle. In all time course experiments cells were fixed and stained with Sam-Yellowe’s trichrome for visualization by light microscopy. Confocal and differential interference contrast (DIC) microscopy was performed to determine cross reactivity of Plasmodium specific antibodies against Colpodella species proteins. Transmission electron microscopy was performed to visualize the ultrastructure of Colpodella sp. The data shows that the duration of Colpodella species life cycle is thirtysix hours. Colpodella sp. were most active between 20-28 hours as Colpodella sp. were iv observed actively swimming, feeding, forming transient cysts, and excysting. Bodo caudatus was observed to excyst and encyst earlier in the culture. Previously undocumented stages were identified in the Colpodella species life cycle. Precyst stages, multinucleate cysts, egress of trophozoites with incomplete cytokinesis, and single nuclei mature cysts were identified. Multinucleate cysts of Colpodella species are reminiscent of Apicomplexa schizonts. Immunofluorescence confirmed there was reactivity between antiserum 686 and Colpodella sp. proteins. Differential interference contrast and transmission electron microscopy identified asynchronous and asymmetric mitosis in Colpodella cysts. Knowledge of the life cycle and stages of Colpodella sp. will allow investigators to perform studies in cell biology and biochemistry of Colpodella species.

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