FIG. 4.

Mutations in EcfT abolish folate and pantothenate uptake. (A) The E. coli pabA abgT strain containing pACYC-RIL, pLmFolT, and a variant of pLmEcfAAT with a wild-type (red circles), R184E (blue circles), R225E (black circles), or R184/225R (green circles) ecfT allele were grown in minimal medium containing no supplement, 10 μM 4-aminobenzoate, or 10 μM 5-formyl-tetrahydrofolate. (B) E. coli DV1 (panD panF) harboring pLacI-RARE2, pLmPanT, and variants of pLmEcfAAT as indicated above was grown in unsupplemented minimal medium or in medium containing 1 μM β-alanine or 1 μM Ca²⁺-pantothenate. All cultures contained 0.5 mM IPTG and were grown in duplicate in microtiter plates at 37°C. Growth was monitored by determining the optical density at 600 nm (OD₆₀₀) and is expressed as the mean of duplicate results. See Fig. 1 for the strain phenotypes.