Fig 4. Growth defect of ΔpyrE mutant in M9 media is restored by uracil supplementation.

(A) Overnight cultures of a ΔpyrE mutant and the wild type, HA431 (HA420 ΔphoN::Kan^R) were washed in M9 minimal broth twice and 3 μl of washed culture was spotted on M9 media with (Uracil+) or without uracil supplementation (Uracil-) (20 mg/L). Plates were incubated overnight at 37^°C. This experiment was performed in triplicate and representative photographs are shown. (B-C) Bacteria (ΔpyrE mutant: filled square, or the wild type wild type, HA431 (HA420 ΔphoN::Kan^R): filled circle) from overnight cultures were washed in M9 broth, and sub-cultured in un-supplemented M9 broth with (solid line) or in M9 broth with uracil supplementation at 20mg/ml (dashed line). At the indicated time points, aliquots were taken for absorbance measurement at 570nm (B), or were serially diluted in PBS and plated on LB supplemented with kanamycin and XP to enumerate CFU (C). Bars indicate mean and error bars indicate standard deviation. All experiments were performed on three separate occasions.