DISSERTATION RESEARCH: Patterns of Thermal Adaptation

该项目旨在确定热适应的模式。为了实现这一目标，研究人员将使用G4噬菌体的实验室种群进行进化实验，G4噬菌体是一种感染大肠杆菌的病毒。研究人员将使病毒种群适应高温和低温，通过对整个基因组进行测序来确定导致适应的突变，并测量进化后的噬菌体在广泛温度范围内的表现。研究人员将确定适应性突变是否倾向于发生在相同或不同的基因中，并提出两个关于热适应的假设。这些假设是：(1)冷适应病毒的最大生长速度比热适应病毒低；(2)适应新的温度将导致在不同温度下的性能损失。这两个预测都源于这样一个想法，即在特定温度下限制或降低有机体的表现的生化反应是有限制的。自然种群对热变化的耐受能力对地理分布和最终物种生存至关重要。在短时间尺度上--每天、季节或每年--温度变化往往是可预测的。然而，世界各地不断变化的温度意味着，未来的温度变化可能不会那么可预测。对热适应的研究应有助于更好地了解全球变暖的影响，并有可能确定面临灭绝危险的种群。

This project aims to identify patterns of thermal adaptation. To accomplish this goal, the investigators will conduct evolution experiments using laboratory populations of the bacteriophage G4, a virus that infects the bacterium E. coli. The investigators will adapt virus populations to high and low temperatures, identify the mutations responsible for adaptation by sequencing whole genomes, and measure the performance of the evolved phages over a wide temperature range. The investigators will determine if the adaptive mutations tend to occur in the same or different genes and address two hypotheses concerning thermal adaptation. These hypotheses are: (1) Cold-adapted viruses will have lower maximal growth rates than hotter- adapted viruses; and (2) Adaptation to a new temperature will result in a loss of performance at different temperatures. Both of these predictions stem from the idea that there are constraints on biochemical reactions that limit or reduce an organism's performance at particular temperatures. The ability of natural populations to tolerate thermal variation is crucial to geographic distribution and ultimately to species survival. Over short time scales--daily, seasonally, or yearly--thermal variation has tended to be predictable. However, changing temperatures across the world mean that thermal variation may not be so predictable in the future. The study of thermal adaptation should lead to a greater understanding of the effects of global warming, and it may be possible to identify populations at risk of extinction.