Dataset for "Growth and metabolism of Chromera velia under hypercapnia": Chromera velia alga videos were taken under reference conditions

Abstract

Abstract Chromera velia, also known as Chromerid, is a spherical golden-brown alga discovered a decade ago by coincidence while examining coral symbionts in Australia, Sydney , the Great Barrier Reef, Australia. Chromera velia has a unique evolutionary position between two different species of dinoflagellates and apicomplexans. Being relatively newly discovered, C. velia is still not fully studied, with previous work focusing on understanding its physical and ecological structures, phylogenetic analysis, and the missing linkage of C. velia and other related species. This thesis extends previous knowledge by exploring environmental factors and responses to increases in CO2 concentration (hypercapnia) (10% and 20%) and light intensities (50, 220, 2,850 lx) on C. velia’s growth in incubated flasks; the light intensity (36, 54, 72 klx) effect on the growth of C. velia in aerated bioreactors was also examined. Atmospheric CO2 concentration was the reference CO2 condition for the effect of hypercapnia, and darkness was the reference condition for the effect of light intensity. These cultures were used to determine the optimal conditions for growth in incubated flasks culture by modelling. The harvested C. velia were analysed to identify bioactive metabolites (carotenoids and fatty acids) because of their influence on human health. The effect of environmental conditions on the carotenoids and fatty acids (FAs) was studied to find the conditions for maximum production. Another aim of this work was to analyse the motility state of C. velia in darkness and hypercapnia (5%, 10%, 20% CO2) under light and time-lapse confocal microscopies, to investigate the initiation time and proportion of flagellation. New morphological features of C. velia were also highlighted. The results of the environmental factors study showed that hypercapnia has a negative effect on the growth of C. velia, yet this alga can still thrive at 10% CO2. Increasing the light intensity elevated the growth rate. Combining the high light intensity with hypercapnia has a significant positive impact on slowing down the decrease in growth rate under hypercapnia. The saturating light is found at the maximum tested light intensities of 2,850 lx in incubated flask culture and 36 klx in aerated bioreactor culture. Under light intensity 2,565 lx and 7% CO2, the near-optimal growth rate was determined to be 0.0415 day-1 with a model validation error of 10%. These findings show that combining hypercapnia with light irradiance helps C. velia adapt to high CO2 levels. This could make C. velia applicable to CO2 absorption from industrial flue gas streams (e.g., power plant emissions) via the incorporation of bioremediation-mitigation algal ponds, therefore contributing to directed efforts to combat global warming. For carotenoids, when investigating the effect of different hypercapnia levels and light intensities on the xanthophyll cycle, both factors were found to have a positive correlation with zeaxanthin but a negative impact on violaxanthin concentration. The maximum zeaxanthin production was identified in incubated flasks to be 1.8×106 ng/ml at 2,850 lx and 20% CO2 and in aerated bioreactor cultures to be 6.7×105 ng/ml in the light intensity range of 36 54 klx. The fatty acid (FA) analysis revealed that the fatty acid profile of C. velia has mostly C18 and C20 components, of which polyunsaturated fatty acids (PUFA) were the most prevalent. Eicosapentaenoic acid (EPA) is found to be the major fatty acid in PUFA. Increasing hypercapnia to 10% has a favourable effect on FAs, as does increasing light intensity. Hypercapnia and light have an interacting effect on C. velia, as evidenced by the FA uneven patterns. Despite the difficulties in understanding the behaviour of FAs in microalgae in general, which has been documented in the literature, a clear image of the ideal C. velia culture conditions for maximum accumulation of each FA component in both incubated flasks and aerated bioreactors could still be seen. Based on the results in this study at lab scale, C. velia was found to be a suitable candidate for commercial scale-up of zeaxanthin and FA synthesis, as well as a solution for industrial gaseous CO2 emissions. An important finding is that zeaxanthin has a direct influence on fatty acid desaturation under elevated hypercapnia. As a result of zeaxanthin increasing the fluidity of the cell beyond its capability, the alga produces SFA to enhance the rigidity of the membrane as a protective mechanism. Chromera velia produced a substantial amount of EPA, suggesting that it may be exploited for commercial EPA production on land. Finally, even though research on C. velia is still in its early stages, the findings of the metabolites analysis reveal a strong link between the increase in zeaxanthin and the degree of FA desaturation in C. velia. According to literature, increasing zeaxanthin increases membrane fluidity in the ordered phase while lowering fluidity in the liquid crystalline phase of phosphatidylcholine during hypercapnia. Algal mechanisms for resolving the osmotic imbalance caused by variations in the saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA) ratio (SFA/PUFA) include reduced membrane fluidity and rigidification of the wall structure. In the motility investigation, hypercapnia accelerated the onset of flagellation and increased the proportion of flagellating alga. Flagellation at a proportion of 90% occurred on day 4 at a CO2 concentration of 20%, which is significantly greater than the reference CO2 condition. The metabolic response hypothesis states that when C. velia is exposed to hypercapnia, it increases the amount of lipid or starch in its cells, which are the main sources of energy for flagellate algae in the dark. The observation of C. velia reveals new insights into the ecology and biodiversity of this alga. Investigating C. velia under the microscope revealed several metabolic characteristics similar to green algae and vascular plants, including red-eye, two types of flagellated cells representing two sexual mating cells (eggplant and round shape), and a double cell wall. These are important findings that show the effect of hypercapnia stress on flagellated algae, and the relationship between this alga and other higher plants on the one hand, and flagellated green algae on the other. Aside from that, C. velia's remarkable survival rate under high CO2 settings highlights the alga's enormous potential to lower the CO2 impact of human activities in aquatic environments. As a result, more research is needed to completely comprehend flagellation in the presence of high CO2 concentrations. The current thesis steers future investigations towards application of C. velia in CO2 emission mitigation (algae carbon capture), the production of bioactive valuable components, and wastewater bioremediation. In C. velia at higher CO2 concentration, a greater proportion of the energy required for photosynthesis is dedicated to producing more fatty acids. Increasing the fatty acids in C. velia provides the required energy to flagellate in complete darkness. Chromera velia is proved to be a potential source for the land-based commercial production of zeaxanthin and PUFA, especially EPA. Interestingly, C. velia was found to share several traits with flagellated green algae, namely their metabolic features and the biosynthetic routes to produce zeaxanthin. This work highlights a new morphological finding that could help in further understanding the missing origin path of apicomplexan parasites from their algal ancestors.