Indirect Fitness Benefits Enable the Spread of Host Genes Promoting Costly Transfer of Beneficial Plasmids
Fig 2
Selection for plasmid transfer through discrimination of recipients.
A: Donor ability to self and others among natural isolates. A normalized donor ability for the R1 plasmid for couples of donor and recipient strains was obtained by correcting conjugation rates from [11] (left of the dashed line) and [12] (right of the dashed line) datasets by the average strain donor ability across all recipient strains tested. Points in red indicate donor ability measured from a strain to itself. B: Conjugation rates between E. coli K12 and B strains. Conjugation rates were measured in the same growth conditions as for Fig 2C competitions. Donors and recipients were mixed during exponential growth (optical density [OD] = 0.2), then donor (D), recipient (R), and transconjugant (T) densities were measured by plating. Conjugation rates were computed as (mL.cell-1.h_1), and are shown as geometric means ± standard error of the mean (SEM) (N ≥10). Red bars show conjugation data obtained with the wild type K12 strain, grey bars show conjugation using the K12ΔarcA mutant. C: Competition between K12 and B strains with antibiotic resistance transfer. The change in frequency of K12 strain is shown in competition with B strain in a single well-mixed population, in the absence (blue) or presence (yellow) of antibiotic selection at the end of competition, and for different initial proportions of the R1-19 plasmid, common to both strains. Pale colours show the outcome of competition with the K12ΔarcA strain. Results are shown as means ± SEM (N ≥10). Data are available from FigShare at http://dx.doi.org/10.6084/m9.figshare.3199252.