FIGURE 6: Glycine does not restore competitive fitness to E. coli ridA tdcF double mutants under 2AA stress. Shown is competitive fitness of an E. coli ridA tdcF double mutant (∆ridA890 tdcF13::Cm) grown in coculture with wild type E. coli in minimal glucose (11 mM) medium with the indicated supplements – L-serine (5 mM), glycine (1 mM), L-isoleucine (1 mM). Data shown are mean and standard deviation of three independent biological replicates. The underlined genotype indicates the strain for which the competitive indices are shown in the corresponding graph. An asterisk (*) indicates a significant difference (p ≤ 0.05 as determined by Sidak’s multiple comparisons test) in CI values compared to control experiments in which ∆ridA890tdcF13::Cm was competed with an isogenic strain lacking ridA and tdcF (∆ridA890 ∆ tdcF14) in each medium.