FIG 1.

Mutations from spontaneously arising mutants confer resistance to growth inhibition by d-amino acids when moved to the parental strain. Optical density of cells grown in shaking MSgg medium was measured in the presence (white diamonds) or absence (black diamonds) of 10 μM d-Tyr. The ppaC^A145V, tyrS riboswitch (tyrS^−38C>T), tyrS^A202V, trnD-Phe^35A>T, and hrcA^−8A>G mutants were constructed by reconstituting select spontaneously arising mutations (Table 1) in the parent strain 3610. Results are shown as a semilog plot and indicate the averages from four replicates. Error bars show the standard deviations.