Bioprocess Engineering and AlgaePARC, Wageningen University and Research, PO Box 16, 6700 AA, Wageningen, The Netherlands.
Bioinformatics Group, Wageningen University and Research, PO Box 633, 6700 AP, Wageningen, The Netherlands.
Sci Rep. 2022 Feb 28;12(1):3290. doi: 10.1038/s41598-022-06954-6.
Photobioreactors heat up significantly during the day due to irradiation by sunlight. High temperatures affect cell physiology negatively, causing reduced growth and productivity. To elucidate the microalgal response to stressful supra-optimal temperature, we studied the physiology of Picochlorum sp. (BPE23) after increasing the growth temperature from 30 °C to 42 °C, whereas 38 °C is its optimal growth temperature. Cell growth, cell composition and mRNA expression patterns were regularly analyzed for 120 h after increasing the temperature. The supra-optimal temperature caused cell cycle arrest for 8 h, with concomitant changes in metabolic activity. Accumulation of fatty acids was observed during this period to store unspent energy which was otherwise used for growth. In addition, the microalgae changed their pigment and fatty acid composition. For example, palmitic acid (C16:0) content in the polar fatty acid fraction increased by 30%, hypothetically to reduce membrane fluidity to counteract the effect of increased temperature. After the relief of cell cycle arrest, the metabolic activity of Picochlorum sp. (BPE23) reduced significantly over time. A strong response in gene expression was observed directly after the increase in temperature, which was dampened in the remainder of the experiment. mRNA expression levels associated with pathways associated with genes acting in photosynthesis, carbon fixation, ribosome, citrate cycle, and biosynthesis of metabolites and amino acids were downregulated, whereas the proteasome, autophagy and endocytosis were upregulated.
由于阳光照射，光生物反应器在白天会显著升温。高温会对细胞生理产生负面影响，导致生长和生产力下降。为了阐明微藻对超适温胁迫的反应，我们研究了在将生长温度从 30°C 升高到 42°C 后，小球藻（BPE23）的生理情况，而 38°C 是其最适生长温度。在升高温度后的 120 小时内，定期分析细胞生长、细胞组成和 mRNA 表达模式。超适温导致细胞周期停滞 8 小时，同时代谢活性发生变化。在此期间积累脂肪酸，以储存未消耗的能量，否则这些能量将用于生长。此外，微藻改变了它们的色素和脂肪酸组成。例如，极性脂肪酸部分中棕榈酸（C16:0）的含量增加了 30%，据推测这是为了降低膜流动性，以抵消温度升高的影响。细胞周期停滞缓解后，小球藻（BPE23）的代谢活性随着时间的推移显著降低。在温度升高后直接观察到基因表达的强烈反应，而在实验的其余部分反应减弱。与光合作用、碳固定、核糖体、柠檬酸循环以及代谢物和氨基酸生物合成相关的途径相关的基因表达下调，而蛋白酶体、自噬和内吞作用上调。
