Bacterial populations differentiate over time and space to form distinct genetic units. The mechanisms governing this diversification are presumed to result from the ecological context of living units to adapt to specific niches. Recently, a model assuming the acquisition of advantageous genes among populations rather than whole genome sweeps has emerged to explain population differentiation. However, the characteristics of these exchanged, or flexible, genes and whether their evolution is driven by adaptive or neutral processes remain controversial. By analysing the flexible genome of single‐amplified genomes of co‐occurring populations of the marine Prochlorococcus HLII ecotype, we highlight that genomic compartments – rather than population units – are characterized by different evolutionary trajectories. The dynamics of gene fluxes vary across genomic compartments and therefore the effectiveness of selection depends on the fluctuation of the effective population size along the genome. Taken together, these results support the drift‐barrier model of bacterial evolution.

中文翻译：

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漂移屏障模型驱动结构化细菌种群的基因组格局。

细菌种群随时间和空间而分化，形成独特的遗传单位。据推测，控制这种多样化的机制是由于居住单元适应特定生态位的生态环境所致。最近，出现了一个模型，该模型假设在人群中获得了有利基因而不是整个基因组扫描，以解释群体分化。但是，这些交换的或灵活的基因的特征以及它们的进化是由适应性过程还是中性过程驱动仍然是有争议的。通过分析海洋Prochlorococcus共生种群单扩增基因组的灵活基因组HLII生态型，我们强调基因组区室而不是种群单位具有不同的进化轨迹。基因通量的动态在整个基因组区室中变化，因此选择的有效性取决于沿着基因组的有效种群大小的波动。综上所述，这些结果支持细菌进化的漂移屏障模型。