Chromochloris zofingiensis (Chlorophyceae) Divides by Consecutive Multiple Fission Cell-Cycle under Batch and Continuous Cultivation

Abstract

Several green algae can divide by multiple fission and spontaneously synchronize their cell cycle with the available light regime. The yields that can be obtained from a microalgal culture are directly affected by cell cycle events. Chromochloris zofingiensis is considered as one of the most promising microalgae for biotechnological applications due to its fast growth and the flexible trophic capabilities. It is intensively investigated in the context of bio-commodities production (carotenoids, storage lipids); however, the pattern of cell-cycle events under common cultivation strategies was not yet characterized for C. zofingiensis. In this study, we have employed fluorescence microscopy to characterize the basic cell-cycle dynamics under batch and continuous modes of phototrophic C. zofingiensis cultivation. Staining with SYBR green—applied in DMSO solution—enabled, for the first time, the clear and simple visualization of polynuclear stages in this microalga. Accordingly, we concluded that C. zofingiensis divides by a consecutive pattern of multiple fission, whereby it spontaneously synchronizes growth and cell division according to the available illumination regime. In high-light continuous culture or low-light batch culture, C. zofingiensis cell-cycle was completed within several light-dark (L/D) cycles (14 h/10 h); however, cell divisions were synchronized with the dark periods only in the high-light continuous culture. In both modes of cultivation, daughter cell release was mainly facilitated by division of 8 and 16-polynuclear cells. The results of this study are of both fundamental and applied science significance and are also important for the development of an efficient nuclear transformation system for C. zofingiensis.

In Silico and Cellular Differences Related to the Cell Division Process between the A and B Races of the Colonial Microalga Botryococcus braunii

“…[77,120]. Multinucleated cells are present in both algae, and the nuclei in mononucleated cells were bigger than the nuclei of the multinucleated cells [120]. In this context, our results are similar and suggest that B. braunii race A colonies may have cells that undergo multiple fission in multinucleated cells.…”

“…and Chromochloris sp. [77,120]. Multinucleated cells are present in both algae, and the nuclei in mononucleated cells were bigger than the nuclei of the multinucleated cells [120].…”

“…In spite of the described differences in the RBR phosphorylation sites between race A and race B, as well as the different number and types of CDKs, there are no results suggesting these differences are related to the presence of multinuclear cells in race A, or with the type of cell division of these strains. The study of the cell cycle of other algae showing binary and multiple fission processes, like R. subcapitata or Chromochloris zofingiensis [120], should give more hints on the role of RBR and CDKs in these processes and their regulation [88].…”

The oleaginous astaxanthin-producing alga Chromochloris zofingiensis: potential from production to an emerging model for studying lipid metabolism and carotenogenesis

“…2 ). The multiple fission cell cycle of C. zofingiensis , resembling Scenedesmus and Desmodesmus , is in the consecutive pattern, under which DNA replication and nuclear division are executed multiple times prior to cell division [ 50 ]. Therefore, polynuclear cells are observed for C. zofingiensis and the number of nucleus within a cell is determined by the number of DNA replication and nuclear division events before cell division.…”

“…Therefore, polynuclear cells are observed for C. zofingiensis and the number of nucleus within a cell is determined by the number of DNA replication and nuclear division events before cell division. When the parental cell wall ruptures, autospores (up to 32) are released spontaneously and enter into the next multiple fission cell cycle [ 50 ]. By contrast, C. reinhardtii has a clustered pattern of multiple fission cell cycle, under which cell division occurs right after nuclear division; therefore, C. reinhardtii generally does not include polynuclear stages [ 51 ].…”