Theoretical Biology, Institute of Integrative Biology (IBZ), ETH Zürich, CH 8092, Zürich, Switzerland.
Theoretical Biology, Institute of Integrative Biology (IBZ), ETH Zürich, CH 8092, Zürich, Switzerland
Mol Biol Evol. 2015 Dec;32(12):3079-88. doi: 10.1093/molbev/msu293. Epub 2014 Dec 23.
Mobile genetic elements such as plasmids are important for the evolution of prokaryotes. It has been suggested that there are differences between functions coded for by mobile genes and those in the "core" genome and that these differences can be seen between plasmids and chromosomes. In particular, it has been suggested that essential genes, such as those involved in the formation of structural proteins or in basic metabolic functions, are rarely located on plasmids. We model competition between genotypically varying bacteria within a single population to investigate whether selection favors a chromosomal location for essential genes. We find that in general, chromosomal locations for essential genes are indeed favored. This is because the inheritance of chromosomes is more stable than that for plasmids. We define the "degradation" rate as the rate at which chance genetic processes, for example, mutation, deletion, or translocation, render essential genes nonfunctioning. The only way in which plasmids can be a location for functioning essential genes is if chromosomal genes degrade faster than plasmid genes. If the two degradation rates are equal, or if plasmid genes degrade faster than chromosomal genes, functioning essential genes will be found only on chromosomes.
移动遗传元件，如质粒，对于原核生物的进化很重要。有人认为，移动基因编码的功能与“核心”基因组中的功能不同，而且这些差异可以在质粒和染色体之间看到。特别是，有人认为，很少有必需基因，如参与结构蛋白形成或基本代谢功能的基因，位于质粒上。我们模拟了单一种群内基因型不同的细菌之间的竞争，以研究选择是否有利于必需基因的染色体位置。我们发现，一般来说，必需基因的染色体位置确实受到青睐。这是因为染色体的遗传比质粒更稳定。我们将“降解”率定义为偶然遗传过程（例如突变、缺失或易位）使必需基因失去功能的速度。质粒可以成为功能必需基因的位置的唯一途径是，如果染色体基因的降解速度快于质粒基因。如果两个降解率相等，或者质粒基因的降解速度快于染色体基因，那么只有在染色体上才能找到功能必需基因。
