Plasmid stability is enhanced by higher-frequency pulses of positive selection



Stevenson, Cagla, Hall, James PJ ORCID: 0000-0002-4896-4592, Brockhurst, Michael A and Harrison, Ellie
(2018) Plasmid stability is enhanced by higher-frequency pulses of positive selection. PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, 285 (1870). 20172497-.

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Abstract

Plasmids accelerate bacterial adaptation by sharing ecologically important traits between lineages. However, explaining plasmid stability in bacterial populations is challenging owing to their associated costs. Previous theoretical and experimental studies suggest that pulsed positive selection may explain plasmid stability by favouring gene mobility and promoting compensatory evolution to ameliorate plasmid cost. Here we test how the frequency of pulsed positive selection affected the dynamics of a mercury-resistance plasmid, pQBR103, in experimental populations of <i>Pseudomonas fluorescens</i> SBW25. Plasmid dynamics varied according to the frequency of Hg<sup>2+</sup> positive selection: in the absence of Hg<sup>2+</sup> plasmids declined to low frequency, whereas pulses of Hg<sup>2+</sup> selection allowed plasmids to sweep to high prevalence. Compensatory evolution to ameliorate the cost of plasmid carriage was widespread across the entire range of Hg<sup>2+</sup> selection regimes, including both constant and pulsed Hg<sup>2+</sup> selection. Consistent with theoretical predictions, gene mobility via conjugation appeared to play a greater role in promoting plasmid stability under low-frequency pulses of Hg<sup>2+</sup> selection. However, upon removal of Hg<sup>2+</sup> selection, plasmids which had evolved under low-frequency pulse selective regimes declined over time. Our findings suggest that temporally variable selection environments, such as those created during antibiotic treatments, may help to explain the stability of mobile plasmid-encoded resistance.

Item Type: Article
Uncontrolled Keywords: experimental evolution, fluctuating selection, compensatory evolution, horizontal gene transfer, plasmid, mercury resistance
Depositing User: Symplectic Admin
Date Deposited: 15 Jan 2019 10:28
Last Modified: 13 Feb 2024 09:13
DOI: 10.1098/rspb.2017.2497
Open Access URL: http://eprints.whiterose.ac.uk/125201/1/FullCombin...
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3031154