Experimental Evolutionary Studies of Temperature Adaptation

对温度的长期进化适应将在大肠杆菌中进行实验测量。最初的创始实验系（祖先）保持在37℃，随后，在2000代暴露于32℃，42℃，每天在它们之间交替，以及保持在37℃的控制系之后，获得了复制系组。这些实验将确定每个这些组适应各自温度的机制。测量的变量将包括合成和运输能力、抗逆性和人口增长表现的变化。还将在较高（42℃）温度下选择线材，以确定热上限是否可以延长，以及相关变化是否会增加耐温性。研究建议解决以下问题：—生物系统对环境变化的进化反应速度有多快？在一种环境中，先前的进化历史是否决定了适应新环境的能力？对特定环境的适应是否通过类似的机制进行，还是有与适应事件一样多的解决方案？本研究涉及的具体问题包括不同热环境下的适应速率和极限、适应进化过程中的权衡程度、历史环境对进一步适应的影响、相似环境下进化过程中机制适应的一致性以及环境对突变过程的影响。

Long-term evolutionary adaptation to temperature will be measured experimentally in the bacterium Escherichia coli. Originally the founding experimental line (the ancestor) was maintained at 37 C. Subsequently, groups of replicated lines were obtained after 2000 generations of exposure to 32 C, 42 C, and a daily alternation between them, as well as control lines which were maintained at 37 C. These experiments will determine the mechanisms by which each of these groups adapted to their respective temperatures. Measured variables will include changes in synthetic and transport capacities, stress resistance, and population growth performance. Lines will also be selected at higher (42 C) temperatures to determine whether the upper thermal limit can be extended and the correlated changes responsible for increased temperature tolerance. The research proposes to address the following questions: --How rapidly can biological systems respond evolutionarily to environmental change? --Does prior evolutionary history in one environment condition or predispose ability to adapt to novel environments? --Does adaptation to a particular environment proceed by similar mechanisms or are there as many solutions as adaptive events? Specific issues addressed by this research include the rate and limits of adaptation in diverse thermal environments, the extent of trade-offs during adaptive evolution, the effect of historical environment on further adaptation, the concordance of mechanistic adaptations during evolution in similar environments, and environmental effects on mutational processes.