Whitaker Rachel J, Grogan Dennis W, Taylor John W
Department of Plant and Microbial Biology, University of California, Berkeley, USA.
Mol Biol Evol. 2005 Dec;22(12):2354-61. doi: 10.1093/molbev/msi233. Epub 2005 Aug 10.
Although microorganisms make up the preponderance of the biodiversity on Earth, the ecological and evolutionary factors that structure microbial populations are not well understood. We investigated the genetic structure of a thermoacidophilic crenarchaeal species, Sulfolobus islandicus, using multilocus sequence analysis of six variable protein-coding loci on a set of 60 isolates from the Mutnovsky region of Kamchatka, Russia. We demonstrate significant incongruence among gene genealogies and a lack of association between alleles consistent with recombination rates greater than the rate of mutation. The observation of high relative rates of recombination suggests that the structure of this natural population does not fit the periodic selection model often used to describe populations of asexual microorganisms. We propose instead that frequent recombination among closely related individuals prevents periodic selection from purging diversity and provides a fundamental cohesive mechanism within this and perhaps other archaeal species.
尽管微生物构成了地球上生物多样性的主体，但构成微生物种群的生态和进化因素却尚未得到充分理解。我们利用对来自俄罗斯堪察加半岛穆特诺夫斯基地区的60个分离株的六个可变蛋白质编码基因座进行多位点序列分析，研究了嗜热嗜酸泉古菌冰岛硫化叶菌的遗传结构。我们证明了基因谱系之间存在显著不一致，并且等位基因之间缺乏关联，这与重组率高于突变率一致。高相对重组率的观察结果表明，这个自然种群的结构不符合通常用于描述无性微生物种群的周期性选择模型。相反，我们提出，亲缘关系密切的个体之间频繁的重组可防止周期性选择清除多样性，并在这个以及其他古菌物种中提供一种基本的凝聚机制。
