Fig. 2.

Fate of AbaRs and natural transformation events within mixed populations. (A) Experimental determination of the cost on fitness of AbaR4 and AbaR1. The effect on fitness of acquisition of AbaR4 and AbaR1 by the M2 strain was measured using bacterial competitions with their parental M2 strain in LB medium or in tryptone-NaCl medium. Selection coefficient (S) of the AbaR-carrying strains was determined relative to the parental M2 strain. Independent measures of selection coefficients are represented by the gray dots, black dots represent mean values, and error bars represent the SE. (B) Frequency of transformation events resulting in the deletion or acquisition of inserts of length from 10 to 16 kb in a wild-type strain and ΔcomM mutant. Equal parts of strains carrying or not the insert are mixed. Following incubation, the frequency of cells not previously carrying the insert and which acquired the insert is determined (acquisition). Similarly, the frequency of cells which have lost the insert (deletion) is determined (Materials and Methods). (C) Frequency of transformation events resulting in the acquisition of a SNP allele conferring resistance to rifampicin. As in A, equal parts of strains carrying or not the allele are mixed. The fraction of cells which acquired the SNP from the other cells is determined by plating (Materials and Methods). (ns: P > 0.05; *: P ≤ 0.05; **: P ≤ 0.01; ***: P ≤ 0.001; ****: P ≤ 0.0001). The detection limit of transformation events is 1 × 10⁻⁸. Boxplots represent the 25th percentile, median, 75th percentile.