Encystment and Excystment in Colpoda inflata: Macronuclear DNA and Total Protein Content Quantitative Variations

Abstract

Cell activities have been investigated in Colpoda inflata strain Na 17, during transition to resting cyst and in the course of a long-lasting encystment, as well as after the first hours following excystment induction. In order to reveal the synthesis both of macronuclear DNA and cell proteins, macronuclear DNA and total protein contents were cytofluorometrically measured in starved pre-cystic organisms, in just formed and in increasingly older cysts, up to 50 days since encystment onset, and, in 5 to 25 days old cysts, after 5 hours from excystment induction. The results suggest that starved cells are able to enter resting encystment at different phases of their cell cycle. Furthermore, not only do macronuclear DNA and protein syntheses take place during transition to the cyst, but also in cysts as old as 27 days. Investigations on the dynamics of excystment indicate that a high chromatin extrusing activity occurs in the macronuclei of excysting cells, after the 70% of the excystment time. Conversely, after only the first quarter of the excystment time, proteins would be utilized possibly to reorganize cortical structures of the excysting cell.