Marais Gabriel A B, Calteau Alexandra, Tenaillon Olivier
Université de Lyon, Centre National de la Recherche Scientifique, UMR5558, Laboratoire de Biométrie et Biologie évolutive, Villeurbanne Cedex, 69622, France.
Genetica. 2008 Oct;134(2):205-10. doi: 10.1007/s10709-007-9226-6. Epub 2007 Nov 29.
Genome reduction has been considered the hallmark of endosymbiotic bacteria, such as endocellular mutualists or obligatory pathogens until it was found exactly the same in several free-living bacteria. In endosymbiotic bacteria genome reduction is mainly attributed to degenerative processes due to small population size. These cannot affect the free-living bacteria with reduced genomes because they are known to have very large population sizes. It has been proposed that selection for simplification drove genome reduction in these free-living bacteria. For at least one of them (Prochlorococcus), genome reduction is associated with accelerated evolution and we suggest an alternative hypothesis based on increase in mutation rate as the primary cause of genome reduction in free-living bacteria.
基因组缩减一直被认为是内共生细菌的标志，如细胞内共生菌或专性病原体，直到在几种自由生活细菌中也发现了完全相同的情况。在内共生细菌中，基因组缩减主要归因于种群规模较小导致的退化过程。这些过程不会影响基因组缩减的自由生活细菌，因为已知它们具有非常大的种群规模。有人提出，对简化的选择推动了这些自由生活细菌的基因组缩减。对于其中至少一种（原绿球藻）来说，基因组缩减与加速进化有关，我们提出了另一种假设，即突变率增加是自由生活细菌基因组缩减的主要原因。
