Vos Michiel, Velicer Gregory J
Max-Planck Institute for Developmental Biology, Tübingen 72076, Germany.
Curr Biol. 2008 Mar 11;18(5):386-91. doi: 10.1016/j.cub.2008.02.050.
Genetic differentiation between spatially separated populations within a species is commonly observed in plants and animals, but its existence in microbes has long been a contentious issue. Traditionally, many microbial ecologists have reasoned that microbes are not limited by dispersal as a result of their immense numbers and microscopic size. In this view, the absence of barriers to gene flow between populations would prevent differentiation of populations by genetic drift and hinder local adaptation. Myxococcus xanthus is a globally distributed, spore-forming bacterium that offers a robust test for genetic differentiation among populations because sporulation is expected to enhance dispersal. Using multi-locus sequence data, we show here that both diversity and the degree of differentiation between populations increase as a function of distance in M. xanthus. Populations are consistently differentiated at scales exceeding 10(2)-10(3) km, and isolation by distance, the divergence of populations by genetic drift due to limited dispersal, is responsible. Our results provide new insights into how genetic diversity within species of free-living microbes is distributed from centimeter to global scales.
在植物和动物中，一个物种内空间隔离的种群之间的遗传分化是普遍存在的现象，但在微生物中这种现象的存在长期以来一直是个有争议的问题。传统上，许多微生物生态学家认为，由于微生物数量众多且体积微小，它们不受扩散的限制。按照这种观点，种群之间基因流动没有障碍会阻止种群因遗传漂变而分化，并阻碍局部适应。黄色粘球菌是一种全球分布的形成孢子的细菌，由于孢子形成有望增强扩散，因此它为种群间的遗传分化提供了一个有力的测试对象。利用多位点序列数据，我们在此表明，黄色粘球菌种群之间的多样性和分化程度均随距离增加而增加。种群在超过10² - 10³千米的尺度上持续分化，并且距离隔离（即由于扩散受限导致种群因遗传漂变而产生的分化）是其原因。我们的结果为自由生活微生物物种内的遗传多样性如何从厘米尺度分布到全球尺度提供了新的见解。
