FIGURE 8: Glycine does not restore competitive fitness to ridA or ridA tdcF mutants in the presence of elevated serine concentrations. Shown are competitive indices of (A) an E. coli ridA mutant (ridA790::kan) and (B) a 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 (20 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 CIs 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 each strain was competed with an isogenic strain lacking the relevant RidA homolog(s) in each medium.