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. 2004 Jan;186(2):343–350. doi: 10.1128/JB.186.2.343-350.2004

FIG. 4.

FIG. 4.

Physiological role of each phenylalanine transport system in E. coli cells grown under various conditions. (A) AroP-, BrnQ-, LIV-I/LS-, and PheP-expressing Phe− strain YG208 (All), LIV-I/LS-expressing Phe− strain YG210 (LIV-I/LS), PheP-expressing Phe− strain YG211 (PheP), AroP-expressing Phe− strain YG212 (AroP), and Phe− strain YG213 not carrying any of these transport systems (None) were streaked on M63-glucose minimal medium plates containing 100 μM phenylalanine (MMF) and on MMF supplemented with 1 mM isoleucine (MMF+I), tryptophan (MMF+W), or tyrosine (MMF+Y). (B) Accumulation of phenylalanine in E. coli cells with various phenylalanine transport systems in the presence of 1 mM tyrosine. Strains MG1655 (□), YG106 (LIV-I/LS) (○), YG108 (PheP) (•), and YG109 (AroP) (▪) were grown in MMF+Y, and after the optical density at 600 nm had reached 0.5, the cells were harvested and suspended in MMF+Y containing 60 μg of chloramphenicol/ml. Cell suspensions were incubated in the presence of 100 μM labeled phenylalanine, and samples were withdrawn at the times indicated. The experiments were repeated three times with essentially the same results; the data for a representative experiment are shown.