Figure 6.

Deletions in subunits of the ATP synthase gene are costly mutations that confer kanamycin resistance. (A) Kanamycin MICs (n = 8, box plots as defined in description of Figure 2C) for the isolates with the deletions (two-sample independent t-tests for wild type against isolates yield P values < 10⁻⁵ for all except isolates L: P = 0.0095 and X: P = 0.000879). Thus, these deletions increase resistance to kanamycin only slightly. (B) Growth curves of the ATP synthase mutants in 8-kan and (C) 0-kan (error bars represent standard deviation from eight replicates; legend from B is applicable throughout the figure). In plain LB, the ATP synthase mutants grow to a much lesser extent than wild type, suggesting a huge cost factor associated with these deletion mutations. The strains with the 108 bp deletion in atpG are able to grow in 8-kan to approximately the same extent as in the absence of kanamycin. Oddly though, isolates H (atpGΔ28) and L (atpGΔ1, atpAΔ15), although possessing a similar mutation (refer Supplementary Figure S11), do not grow well in 8-kan. This is consistent with these strains not being picked up in the P1 (Fig. 4), although limited sampling could also result in this.