Evolution of high mutation rates in experimental populations of E. coli

The outcomes of evolution are determined by a stochastic dynamical process that governs how mutations arise and spread through a population. Here, we analyze the dynamics of molecular evolution in twelve experimental populations of Escherichia coli, using whole-genome metagenomic sequencing at 500-generation intervals through 60,000 generations. Despite a declining rate of fitness gain, molecular evolution continues to be characterized by signatures of rapid adaptation, with multiple beneficial variants simultaneously competing for dominance in each population. Interactions between ecological and evolutionary processes play an important role, as long-term quasi-stable coexistence arises spontaneously in most populations, and evolution continues within each clade. We also present new evidence that the targets of natural selection change over time, as epistasis and historical contingency alter the strength of selection on different genes. Together, these results show that long-term adaptation to a constant environment can be a more complex and dynamic process than is often assumed.

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“…Six populations evolved a mutator phenotype 4,19 , producing a sudden jump in total derived allele frequency (Fig. 2b).…”

Section: Reconstructing the Molecular Fossil Recordmentioning

confidence: 99%

The dynamics of molecular evolution over 60,000 generations

Good

McDonald

Barrick

et al. 2017

Nature

Self Cite

645

839

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“…A number of experimental and theoretical studies have shown that individuals with high mutation rates can have a selective advantage in changing environments [70][71][72]. Indeed, models predict that the random appearance of a mutator allele can accelerate the adaptive evolution of an entire population [73].…”

Section: Summary and Significancementioning

confidence: 99%

Stress responses and genetic variation in bacteria

Foster

2005

Mutation Research/Fundamental and Molecular Mechanisms of Mutag

176

106

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Under stressful conditions mechanisms that increase genetic variation can bestow a selective advantage. Bacteria have several stress responses that provide ways in which mutation rates can be increased. These include the SOS response, the general stress response, the heat-shock response, and the stringent response, all of which impact the regulation of error-prone polymerases. Adaptive mutation appears to be process by which cells can respond to selective pressure specifically by producing mutations. In Escherichia coli strain FC40 adaptive mutation involves the following inducible components: (i) a recombination pathway that generates mutations; (ii) a DNA polymerase that synthesizes error-containing DNA; and (iii) stress responses that regulate cellular processes. In addition, a subpopulation of cells enters into a state of hypermutation, giving rise to about 10% of the single mutants and virtually all of the mutants with multiple mutations. These bacterial responses have implications for the development of cancer and other genetic disorders in higher organisms.

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“…Simulations have shown how mutators could spread through asexual populations by hitch-hiking with beneficial mutations (Taddei et al, 1997;Tenaillon et al, 1999). They have also been demonstrated to increase the rate of adaptive evolution, at least in certain conditions (de Visser et al, 1999), though others have found that mutator lines did not differ in fitness (Sniegowski et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Sexual selection and the evolution of evolvability

Petrie

Roberts

2006

Heredity

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Here we show that sexual selection can have an effect on the rate of mutation. We simulated the fate of a genetic modifier of the mutation rate in a sexual population with and without sexual selection (modelled using a female choice mechanism). Female choice for 'good genes' should reduce variability among male subjects, leaving insufficient differences to maintain female preferences. However, female choice can actually increase genetic variability by supporting a higher mutation rate in sexually selected traits. Increasing the mutation rate will be selected against because of the resulting decline in mean fitness. However, it also increases the probability of rare beneficial mutations arising, and mating skew caused by female preferences for male subjects carrying those beneficials with few deleterious mutations ('good genes') can lead to a mutation rate above that expected under natural selection. A choice of two male subjects was sufficient for there to be a twofold increase in the mutation rate as opposed to a decrease found under random mating.

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Evolution of high mutation rates in experimental populations of E. coli

Cited by 831 publications

References 28 publications

The dynamics of molecular evolution over 60,000 generations

The dynamics of molecular evolution over 60,000 generations

Stress responses and genetic variation in bacteria

Sexual selection and the evolution of evolvability

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