Elimination of Canonical Amino Acid from Escherichia coli by Experimental Evolution

在遗传密码进化的所有理论中，人们假设氨基酸的数量已经从几个逐渐增加到现在构成活细胞蛋白质的20个。这项研究的目的是重建一个可能的进化中间体，在这个中间体中，一个活的有机体含有19个氨基酸，而不是20个氨基酸。这一目标将使人们深入了解蛋白质结构如何适应突变，并在设计和选择适应不同化学成分的有机体方面打开可能性。基于最近实验的令人鼓舞的结果，这一目标将通过对种群施加选择性压力来实现，因为丢失了给定的氨基酸。已经设计了两种不同的策略来替换大肠杆菌中的异亮氨酸为valine和苏氨酸为丝氨酸。这些策略结合了利用经典菌株构建的选择策略和允许长期实验的连续培养设备的使用。

In all the theories of the evolution of the genetic code, the number of amino acids is hypothesized to have gradually increased from a few to the twenty that now constitute the building-blocks of proteins in living cells. The objective of this research is to recreate a possible evolutionary intermediate in which a living organism contains 19 and not 20 amino acids. This objective would give insight into how protein structures adapt to mutation and open possibilities in terms of designing and selecting organisms adapted to a different chemical composition. Based on encouraging results from recent experiments, this objective will be accomplished by placing a population under selective pressure for the loss of a given amino acid. Two different strategies have been designed to replace isoleucine by valine and threonine by serine in Escherichia coli. These strategies combine selection strategies that exploit classical strain constructions with the use of a continuous culture apparatus that allows long-term experiments.