FIG. 3.

Growth of E. coli RK105 with exogenous heme. Overnight cultures of E. coli RK105 (Δccm ΔhemA) or cultures containing pHPEX2 and pRGK333 (A) or pRGK334 (B) were diluted into media without ALA or heme. The cultures were incubated aerobically at 37°C for 2.5 h to exhaust the ALA. Heme was added at the concentrations indicated, and growth (A₆₀₀) was measured. For reference, the growth of E. coli RK103 (wild type) containing either pRGK333 or pRGK334 is shown (⧫). SysI, system I; SysII, system II.