Fig 3. ΔpyrE mutant grows poorly in M9 minimal media.

Growth was tested in vitro by individual growth (A) or competitive growth with wild type (B). (A) Stationary phase cultures of the ΔpyrE mutant (open square) and wild type, HA431 (HA420 ΔphoN::Kan^R) (dark grey triangle) were sub-cultured in LB (solid line) or M9 broth (dotted line) supplemented with kanamycin for 24 hours. Overnight cultures were washed in M9 broth twice prior to sub-culturing in M9 broth. At the indicated time points, CFU in each culture was enumerated after serial dilution and plating. (B) Overnight cultures of ΔpyrE mutant and the wild type (HA431) were washed twice with M9 broth and mixed at 1:1 ratio in M9 broth. Resulting mixture was sub-cultured in M9 broth supplemented with kanamycin at 37^°C for 24h. At the indicated time points the CFU of both strains was enumerated by serial dilution and plating. Dataare shown as ratio of mutant to wild type recovered normalized by the input ratio, and converted logarithmically. Statistical significance was determined by using a Student’s two-tail t-test with p< 0.05 (*) and error bars denote standard error. Experiments were performed on three independent occasions.