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High-Resolution Comparison of Bacterial Conjugation Frequencies
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Variable plasmid fitness effects and mobile genetic element dynamics across Pseudomonas species

Anastasia Kottara, James P J Hall, Ellie Harrison

    FEMS Microbiology Ecology
    |December 12, 2017
    PubMed

    Insights

    Mobile genetic elements (MGE) like plasmids drive bacterial evolution through horizontal gene transfer (HGT). Their stability varies greatly by host species and environment, impacting gene mobility and bacterial adaptation.

    Area of Science:

    • Microbiology
    • Bacterial Genetics
    • Evolutionary Biology

    Background:

    • Mobile genetic elements (MGEs), including plasmids and transposons, are key drivers of bacterial evolution and adaptation.
    • Horizontal gene transfer (HGT) mediated by MGEs facilitates the spread of genes within and between bacterial species.
    • Understanding the dynamics of MGEs across diverse bacterial hosts is crucial for comprehending bacterial evolution and adaptation.

    Purpose of the Study:

    • To investigate the dynamics of a conjugative plasmid (pQBR103) and a transposon (Tn5042) across five different Pseudomonas species.
    • To assess the impact of host species and environmental conditions (mercury selection) on plasmid stability and transposon dynamics.
    • To determine how plasmid-host interactions influence the chromosomal capture of MGEs and subsequent HGT.

    Main Methods:

    • Comparative analysis of plasmid pQBR103 and Tn5042 transposon dynamics in five Pseudomonas species.
    • Experimental evolution under controlled conditions with and without mercury selection.
    • Monitoring plasmid stability, fitness effects, and frequency of chromosomal integration of Tn5042.

    Main Results:

    • Plasmid stability and fitness effects varied significantly across Pseudomonas species and environments.
    • Pseudomonas fluorescens and Pseudomonas savastanoi stably maintained the plasmid, while it was unstable in P. aeruginosa and P. putida.
    • Under mercury selection, Tn5042 was chromosomally captured in unstable hosts, leading to plasmid loss and invasion of plasmid-free genotypes.

    Conclusions:

    • Plasmid stability is contingent on specific plasmid-host genetic interactions, not solely a plasmid property.
    • MGE dynamics in natural bacterial communities are complex and likely influenced by species capable of stable plasmid maintenance, acting as HGT hubs.
    • Host-specific MGE dynamics shape bacterial evolution and the spread of genetic traits like antibiotic resistance.
    Keywords:
    bacteria-plasmid coevolutionconjugative plasmidsexperimental evolutionhorizontal gene transfermobile genetic elements

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