Streamlining and simplification of microbial genome architecture

被引:179
作者
Lynch, Michael [1 ]
机构
[1] Indiana Univ, Dept Biol, Bloomington, IN 47405 USA
关键词
genome evolution; genomic streamlining; mutation; prokaryotes; random genetic drift; recombination;
D O I
10.1146/annurev.micro.60.080805.142300
中图分类号
Q93 [微生物学];
学科分类号
071005 ; 100705 ;
摘要
The genomes of unicellular species, particularly prokaryotes, are greatly reduced in size and simplified in terms of gene structure relative to those of multicellular eukaryotes. Arguments proposed to explain this disparity include selection for metabolic efficiency and elevated rates of deletion in microbes, but the evidence in support of these hypotheses is at best equivocal. An alternative explanation based on fundamental population-genetic principles is proposed here. By increasing the mutational target sizes of associated genes, most forms of nonfunctional DNA are opposed by weak selection. Free-living microbial species have elevated effective population sizes, and the consequent reduction in the power of random genetic drift appears to be sufficient to enable natural selection to inhibit the accumulation of excess DNA. This hypothesis provides a potentially unifying explanation for the continuity in genomic scaling from prokaryotes to multicellular eukaryotes, the divergent patterns of mitochondrial evolution in animals and land plants, and various aspects of genomic modification in microbial endosymbionts.
引用
收藏
页码:327 / 349
页数:23
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