Dissertation Research: Consequences of Evolutionary Specialization in Experimental Long-Term Evolving Populations of Escherichia coli

人们通常认为，生物体的进化专门化必然导致其在其他环境中丧失性能和功能，但很少有证据支持这一理论。这种不确定性部分源于认知问题：如何在操作上定义专家？此外，直接实验的缺乏限制了对可能导致这种功能丧失的其他种群遗传过程的考虑。我们在这里描述了一个长期的实验，在这个实验中，12个细菌种群，大肠杆菌，在实验室里进化了2万代。在这段时间里，所有的种群都逐渐更好地适应了简单的葡萄糖限制环境的生长。我们将研究这种进化对细菌利用除葡萄糖以外的各种底物的能力的影响，从而量化专业化导致功能丧失的程度。我们还将评估两种种群过程，权衡（拮抗多效性）和漂移（突变积累）对观察到的功能变化的相对贡献。

Lenski9801538It is often assumed that evolutionary specialization by an organism must lead to losses of performance and functionality in other environments, but there is little evidence to support this theory. Part of this uncertainty stems from a problem of perception: how does one operationally define a specialist? Also, a paucity of direct experimentation has limited the consideration of alternative population genetic processes that can lead to such losses of function. We describe here a long-term experiment in which twelve populations of the bacterium, Escherichia coli, have evolved in the laboratory for 20,000 generations. During this time, all of the populations became progressively better adapted to growth in a simple glucose-limited environment. We will examine the consequences of this evolution for the bacteria's capacity to utilize a variety of substrates other than glucose, and thereby quantify the extent to which specialization led to losses of function. We will also evaluate the relative contributions of two population processes, tradeoffs (antagonistic pleiotropy) and drift (mutation accumulation), to the observed changes in function.