Opposing effects of final population density and stress on Escherichia coli mutation rate

Krašovec, Rok, Richards, Huw, Gifford, Danna R., Belavkin, Roman V. ORCID: https://orcid.org/0000-0002-2356-1447, Channon, Alastair, Aston, Elizabeth, McBain, Andrew J. and Knight, Christopher G. (2018) Opposing effects of final population density and stress on Escherichia coli mutation rate. The ISME journal, 12 (12) . pp. 2981-2987. ISSN 1751-7362 [Article] (doi:10.1038/s41396-018-0237-3)

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Abstract

Evolution depends on mutations. For an individual genotype, the rate at which mutations arise is known to increase with various stressors (stress-induced mutagenesis-SIM) and decrease at high final population density (density-associated mutation-rate plasticity-DAMP). We hypothesised that these two forms of mutation-rate plasticity would have opposing effects across a nutrient gradient. Here we test this hypothesis, culturing Escherichia coli in increasingly rich media. We distinguish an increase in mutation rate with added nutrients through SIM (dependent on error-prone polymerases Pol IV and Pol V) and an opposing effect of DAMP (dependent on MutT, which removes oxidised G nucleotides). The combination of DAMP and SIM results in a mutation rate minimum at intermediate nutrient levels (which can support 7 × 10  cells ml ). These findings demonstrate a strikingly close and nuanced relationship of ecological factors-stress and population density-with mutation, the fuel of all evolution.

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