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Metabolite toxicity determines the pace of molecular evolution within microbial populations.

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Lilja Elin E, Johnson David R,
Project Metabolic specialization and the causes of diversity in microbial ecosystems
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Original article (peer-reviewed)

Journal BMC Evolutionary Biology
Volume (Issue) 17
Page(s) 52
Title of proceedings BMC Evolutionary Biology

Open Access

URL https://bmcevolbiol.biomedcentral.com/articles/10.1186/s12862-017-0906-2
Type of Open Access Publisher (Gold Open Access)

Abstract

Background The production of toxic metabolites has shaped the spatial and temporal arrangement of metabolic processes within microbial cells. While diverse solutions to mitigate metabolite toxicity have evolved, less is known about how evolution itself is affected by metabolite toxicity. We hypothesized that the pace of molecular evolution should increase as metabolite toxicity increases. At least two mechanisms could cause this. First, metabolite toxicity could increase the mutation rate. Second, metabolite toxicity could increase the number of available mutations with large beneficial effects that selection could act upon (e.g., mutations that provide tolerance to toxicity), which consequently would increase the rate at which those mutations increase in frequency. Results We tested this hypothesis by experimentally evolving the bacterium Pseudomonas stutzeri under denitrifying conditions. The metabolite nitrite accumulates during denitrification and has pH-dependent toxic effects, which allowed us to evolve P. stutzeri at different magnitudes of nitrite toxicity. We demonstrate that increased nitrite toxicity results in an increased pace of molecular evolution. We further demonstrate that this increase is generally due to an increased number of available mutations with large beneficial effects and not to an increased mutation rate. Conclusions Our results demonstrate that the production of toxic metabolites can have important impacts on the evolutionary processes of microbial cells. Given the ubiquity of toxic metabolites, they could also have implications for understanding the evolutionary histories of biological organisms.
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