Abstract
Mobile genetic elements (MGE) such as plasmids and transposons mobilise genes within and between species, playing a crucial role in bacterial evolution via horizontal gene transfer (HGT). Currently, we lack data on variation in MGE dynamics across bacterial host species. We tracked the dynamics of a large conjugative plasmid, pQBR103, and its Tn5042 mercury resistance transposon, in five diverse Pseudomonas species in environments with and without mercury selection. Plasmid fitness effects and stability varied extensively between host species and environments, as did the propensity for chromosomal capture of the Tn5042 mercury resistance transposon associated with loss of the plasmid. Whereas Pseudomonas fluorescens and Pseudomonas savastanoi stably maintained the plasmid in both environments, the plasmid was highly unstable in Pseudomonas aeruginosa and Pseudomonas putida, where plasmid-free genotypes with Tn5042 captured to the chromosome invaded to higher frequency under mercury selection. These data confirm that plasmid stability is dependent upon the specific genetic interaction of the plasmid and host chromosome rather than being a property of plasmids alone, and moreover imply that MGE dynamics in diverse natural communities are likely to be complex and driven by a subset of species capable of stably maintaining plasmids that would then act as hubs of HGT.
Highlights
Bacterial evolutionary innovation and adaptation is often dependent upon the acquisition of novel accessory genes carried on mobile genetic elements (MGE) (Frost et al 2005)
We report that the fitness effects of plasmid carriage and Mobile genetic elements (MGE) dynamics varied extensively between the different Pseudomonas species, indicating that plasmid-host dynamics are governed by species-specific interactions between plasmids and the host chromosome
1994); P. putida KT2440 is a derivative of the toluene degrading and soil isolate P. putida mt-2 (Nakazawa and Yokota 1973); P. savastanoi pv. phaseolicola 1448A is a plant-associated isolate and pathogen of the common bean (Arnold et al 2011); P. stutzeri JM300 (DSM10701) is a denitrifying soil isolate (Busquets et al 2012); P. aeruginosa PAO1 is a derivative of the original Australian PAO that was isolated from a wound in Alfred hospital in Melbourne (Holloway 1955)
Summary
Bacterial evolutionary innovation and adaptation is often dependent upon the acquisition of novel accessory genes carried on mobile genetic elements (MGE) (Frost et al 2005). This fundamental evolutionary process is termed horizontal gene transfer (HGT) (Thomas and Nielsen 2005). Received: 11 August 2017; Accepted: 30 November 2017 C FEMS 2017.
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