Baeza Marcelo, Zúñiga Sergio, Peragallo Vicente, Gutierrez Fernando, Barahona Salvador, Alcaino Jennifer, Cifuentes Víctor
Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago, Chile.
Centro de Biotecnología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile.
Front Microbiol. 2022 Feb 23;13:828536. doi: 10.3389/fmicb.2022.828536. eCollection 2022.
Microorganisms have evolved to colonize all biospheres, including extremely cold environments, facing several stressor conditions, mainly low/freezing temperatures. In general, terms, the strategies developed by cold-adapted microorganisms include the synthesis of cryoprotectant and stress-protectant molecules, cold-active proteins, especially enzymes, and membrane fluidity regulation. The strategy could differ among microorganisms and concerns the characteristics of the cold environment of the microorganism, such as seasonal temperature changes. Microorganisms can develop strategies to grow efficiently at low temperatures or tolerate them and grow under favorable conditions. These differences can be found among the same kind of microorganisms and from the same cold habitat. In this work, eight cold-adapted yeasts isolated from King George Island, subAntarctic region, which differ in their growth properties, were studied about their response to low temperatures at the transcriptomic level. Sixteen ORFeomes were assembled and used for gene prediction and functional annotation, determination of gene expression changes, protein flexibilities of translated genes, and codon usage bias. Putative genes related to the response to all main kinds of stress were found. The total number of differentially expressed genes was related to the temperature variation that each yeast faced. The findings from multiple comparative analyses among yeasts based on gene expression changes and protein flexibility by cellular functions and codon usage bias raise significant differences in response to cold among the studied Antarctic yeasts. The way a yeast responds to temperature change appears to be more related to its optimal temperature for growth (OTG) than growth velocity. Yeasts with higher OTG prepare to downregulate their metabolism to enter the dormancy stage. In comparison, yeasts with lower OTG perform minor adjustments to make their metabolism adequate and maintain their growth at lower temperatures.
微生物已经进化到能够在包括极端寒冷环境在内的所有生物圈中定殖，面临多种应激条件，主要是低温/冷冻温度。一般来说，适应寒冷的微生物所采用的策略包括合成冷冻保护剂和应激保护剂分子、冷活性蛋白，尤其是酶，以及调节膜流动性。不同微生物的策略可能有所不同，这与微生物所处寒冷环境的特征有关，比如季节性温度变化。微生物可以制定策略在低温下高效生长或耐受低温，并在有利条件下生长。这些差异可以在同一种微生物以及来自同一寒冷栖息地的微生物中发现。在这项研究中，从南极亚区乔治王岛分离出了八种生长特性不同的适应寒冷的酵母，对它们在转录组水平上对低温的反应进行了研究。组装了16个开放阅读框文库，并用于基因预测和功能注释、基因表达变化的测定、翻译基因的蛋白质柔韧性以及密码子使用偏好性分析。发现了与对所有主要应激反应相关的推定基因。差异表达基因的总数与每种酵母所面临的温度变化有关。基于基因表达变化、细胞功能的蛋白质柔韧性以及密码子使用偏好性对酵母进行的多项比较分析结果表明，所研究的南极酵母在对寒冷的反应上存在显著差异。酵母对温度变化的反应方式似乎与其最佳生长温度（OTG）的关系比与生长速度的关系更大。OTG较高的酵母准备下调其代谢以进入休眠阶段。相比之下，OTG较低的酵母进行较小的调整以使它们的代谢足够，并在较低温度下维持生长。
