Temperature is the most critical factor that directly affects the physiological functioning and metabolic activities of any organism. With rising global temperature, understanding the heat stress response of an organism is critically important. In the present study, we investigated differences in the early changes occurring upon heat stress in the green microalga Acutodesmus dimorphus, a potential strain for biofuel production. The cells were heat-stressed at 45 and 50°C for 24 h and the temporal response of cells in terms of growth, pigments content, levels of oxidative stress biomarkers i.e., reactive oxygen species (ROS) and the response of enzymatic and non-enzymatic antioxidant scavengers were evaluated. The results revealed that after 24 h of heat stress at 45°C, the accumulations of chlorophyll-a and carotenoids remained stable; all three ROS increased with the higher activities of various enzymatic and non-enzymatic antioxidants. On the contrary, at a higher temperature of 50°C, the accumulations of chlorophyll-a, carotenoids, and non-enzymatic antioxidants reduced drastically while the accumulations of all three ROS and the response of enzymatic antioxidants were significantly higher than those at 45°C. These results suggest that the cells utilize several stress acclimatization mechanisms to cope up the heat stress. There was a dramatic difference in the physiological changes and cellular antioxidant mechanism upon heat stress at 45 and 50°C. The cellular defence response of A. dimorphus gets impaired after heat stress at 50°C but remains active at 45°C, exhibiting the heat resistance and, thus, the thermotolerance. This article is protected by copyright. All rights reserved.

中文翻译：

---

绿色微藻 Acutodesmus dimorphus 对温度诱导的氧化应激条件的生理反应

温度是直接影响任何生物体生理功能和代谢活动的最关键因素。随着全球气温升高，了解生物体的热应激反应至关重要。在本研究中，我们调查了绿色微藻 Acutodesmus dimorphus（一种潜在的生物燃料生产菌株）在热应激时发生的早期变化的差异。细胞在 45°C 和 50°C 下热应激 24 小时，细胞在生长、色素含量、氧化应激生物标志物（即活性氧 (ROS) 水平）以及酶促和非酶促反应方面的时间响应。评估了酶促抗氧化剂清除剂。结果表明，45℃热应激24小时后，叶绿素a和类胡萝卜素的积累量保持稳定；所有三种 ROS 都随着各种酶促和非酶促抗氧化剂的活性升高而增加。相反，在 50°C 的较高温度下，叶绿素-a、类胡萝卜素和非酶抗氧化剂的积累急剧减少，而所有 3 种 ROS 的积累和酶促抗氧化剂的反应都显着高于 45° C。这些结果表明细胞利用几种应激驯化机制来应对热应激。在 45 和 50°C 的热应激下，生理变化和细胞抗氧化机制存在显着差异。A. dimorphus 的细胞防御反应在 50°C 热应激后受损，但在 45°C 时仍保持活跃，表现出耐热性，从而表现出耐热性。本文受版权保护。