近日，美国印第安纳大学J. T. Lennon小组揭示出一个最小细胞的演化。相关论文于2023年7月5日在线发表在《自然》杂志上。

研究人员报告了一个工程化的最小细胞与它所合成的支原体非最小细胞相比是如何与演化的力量抗衡的。突变率是所有报告的细菌中最高的，但没有受到基因组最小化的影响。基因组精简的代价很高，导致适应力下降超过50%，但这一不足在2000代的演化过程中被重新获得。尽管选择作用于不同的遗传目标，但合成细胞的最大生长速度的增加是相当的。此外，当用相对适应力来评估性能时，最小细胞比非最小细胞的演化速度快39%。唯一明显的限制涉及细胞大小的演化。非最小细胞的大小增加了80%，而最小细胞则保持不变。

这种模式反映了ftsZ突变的表观效应，ftsZ编码一个调节细胞分裂和形态的微管蛋白同源物。这些研究结果表明，自然选择可以迅速提高最简单自主生长生物体之一的生存能力。了解具有小型基因组的物种是如何克服演化挑战的，对宿主相关的内生生物的持久性、生物技术精简底盘的稳定性以及合成工程细胞的有针对性的细化提供了关键的见解。

据介绍，只拥有基本基因的最小细胞可以揭示出对生命的持续和稳定至关重要的机制和过程。

附：英文原文

Title: Evolution of a minimal cell

Author: Moger-Reischer, R. Z., Glass, J. I., Wise, K. S., Sun, L., Bittencourt, D. M. C., Lehmkuhl, B. K., Schoolmaster, D. R., Lynch, M., Lennon, J. T.

Issue&Volume: 2023-07-05

Abstract: Possessing only essential genes, a minimal cell can reveal mechanisms and processes that are critical for the persistence and stability of life1,2. Here we report on how an engineered minimal cell3,4 contends with the forces of evolution compared with the Mycoplasma mycoides non-minimal cell from which it was synthetically derived. Mutation rates were the highest among all reported bacteria, but were not affected by genome minimization. Genome streamlining was costly, leading to a decrease in fitness of greater than 50%, but this deficit was regained during 2,000 generations of evolution. Despite selection acting on distinct genetic targets, increases in the maximum growth rate of the synthetic cells were comparable. Moreover, when performance was assessed by relative fitness, the minimal cell evolved 39% faster than the non-minimal cell. The only apparent constraint involved the evolution of cell size. The size of the non-minimal cell increased by 80%, whereas the minimal cell remained the same. This pattern reflected epistatic effects of mutations in ftsZ, which encodes a tubulin-homologue protein that regulates cell division and morphology5,6. Our findings demonstrate that natural selection can rapidly increase the fitness of one of the simplest autonomously growing organisms. Understanding how species with small genomes overcome evolutionary challenges provides critical insights into the persistence of host-associated endosymbionts, the stability of streamlined chassis for biotechnology and the targeted refinement of synthetically engineered cells2,7,8,9.

DOI: 10.1038/s41586-023-06288-x

Source: https://www.nature.com/articles/s41586-023-06288-x