Pal Csaba, Maciá María D, Oliver Antonio, Schachar Ira, Buckling Angus
Department of Zoology, University of Oxford, Oxford OX1 3PS, UK.
Nature. 2007 Dec 13;450(7172):1079-81. doi: 10.1038/nature06350. Epub 2007 Dec 2.
Bacteria with greatly elevated mutation rates (mutators) are frequently found in natural and laboratory populations, and are often associated with clinical infections. Although mutators may increase adaptability to novel environmental conditions, they are also prone to the accumulation of deleterious mutations. The long-term maintenance of high bacterial mutation rates is therefore likely to be driven by rapidly changing selection pressures, in addition to the possible slow transition rate by point mutation from mutators to non-mutators. One of the most likely causes of rapidly changing selection pressures is antagonistic coevolution with parasites. Here we show whether coevolution with viral parasites could drive the evolution of bacterial mutation rates in laboratory populations of the bacterium Pseudomonas fluorescens. After fewer than 200 bacterial generations, 25% of the populations coevolving with phages had evolved 10- to 100-fold increases in mutation rates owing to mutations in mismatch-repair genes; no populations evolving in the absence of phages showed any significant change in mutation rate. Furthermore, mutator populations had a higher probability of driving their phage populations extinct, strongly suggesting that mutators have an advantage against phages in the coevolutionary arms race. Given their ubiquity, bacteriophages may play an important role in the evolution of bacterial mutation rates.
突变率大幅升高的细菌（突变体）在自然种群和实验室种群中经常被发现，并且常常与临床感染有关。尽管突变体可能会增加对新环境条件的适应性，但它们也容易积累有害突变。因此，除了可能存在的从突变体到非突变体的点突变缓慢转变率之外，细菌高突变率的长期维持可能是由快速变化的选择压力驱动的。快速变化的选择压力最可能的原因之一是与寄生虫的拮抗协同进化。在这里，我们展示了与病毒寄生虫的协同进化是否会推动荧光假单胞菌实验室种群中细菌突变率的进化。在不到200代细菌繁殖之后，25%与噬菌体协同进化的种群由于错配修复基因的突变，其突变率提高了10到100倍；在没有噬菌体的情况下进化的种群中，没有一个种群的突变率有任何显著变化。此外，突变体种群使它们的噬菌体种群灭绝的可能性更高，这有力地表明在协同进化的军备竞赛中，突变体对噬菌体具有优势。鉴于噬菌体无处不在，它们可能在细菌突变率的进化中发挥重要作用。
