Baeza Marcelo, Zúñiga Sergio, Peragallo Vicente, 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. 2021 Feb 5;12:623171. doi: 10.3389/fmicb.2021.623171. eCollection 2021.
Microorganisms inhabiting cold environments have evolved strategies to tolerate and thrive in those extreme conditions, mainly the low temperature that slow down reaction rates. Among described molecular and metabolic adaptations to enable functioning in the cold, there is the synthesis of cold-active proteins/enzymes. In bacterial cold-active proteins, reduced proline content and highly flexible and larger catalytic active sites than mesophylls counterparts have been described. However, beyond the low temperature, microorganisms' physiological requirements may differ according to their growth velocities, influencing their global protein compositions. This hypothesis was tested in this work using eight cold-adapted yeasts isolated from Antarctica, for which their growth parameters were measured and their draft genomes determined and bioinformatically analyzed. The optimal temperature for yeasts' growth ranged from 10 to 22°C, and yeasts having similar or same optimal temperature for growth displayed significative different growth rates. The sizes of the draft genomes ranged from 10.7 ( sp.) to 30.7 Mb (), and the GC contents from 37 () to 60% (). Putative genes related to various kinds of stress were identified and were especially numerous for oxidative and cold stress responses. The putative proteins were classified according to predicted cellular function and subcellular localization. The amino acid composition was compared among yeasts considering their optimal temperature for growth and growth rates. In several groups of predicted proteins, correlations were observed between their contents of flexible amino acids and both the yeasts' optimal temperatures for growth and their growth rates. In general, the contents of flexible amino acids were higher in yeasts growing more rapidly as their optimal temperature for growth was lower. The contents of flexible amino acids became lower among yeasts with higher optimal temperatures for growth as their growth rates increased.
栖息于寒冷环境中的微生物已经进化出在这些极端条件下耐受并茁壮成长的策略，主要是应对减缓反应速率的低温。在已描述的使微生物能够在低温下起作用的分子和代谢适应性变化中，有冷活性蛋白/酶的合成。在细菌冷活性蛋白中，脯氨酸含量降低，并且与叶肉对应物相比，具有高度灵活且更大的催化活性位点。然而，除了低温之外，微生物的生理需求可能因其生长速度而异，这会影响它们的整体蛋白质组成。在这项工作中，使用从南极洲分离出的八种适应寒冷的酵母对这一假设进行了测试，测定了它们的生长参数，确定了它们的基因组草图并进行了生物信息学分析。酵母生长的最佳温度范围为10至22°C，具有相似或相同最佳生长温度的酵母显示出显著不同的生长速率。基因组草图的大小范围为10.7（种）至30.7 Mb（），GC含量范围为37（）至60%（）。鉴定出了与各种应激相关的推定基因，尤其是在氧化应激和冷应激反应方面数量众多。根据预测的细胞功能和亚细胞定位对推定蛋白质进行分类。考虑到酵母的最佳生长温度和生长速率，比较了它们之间的氨基酸组成。在几组预测蛋白质中，观察到它们的柔性氨基酸含量与酵母的最佳生长温度及其生长速率之间存在相关性。一般来说，随着最佳生长温度降低，生长较快的酵母中柔性氨基酸的含量较高。随着生长速率增加，最佳生长温度较高的酵母中柔性氨基酸的含量降低。
