Control of the availability of exogenous 5-aminolevulinic acid in Escherichia coli

We observed novel phenomena on the growth of a hemA deletion mutant (H500) of Escherichia coli: First, H500 cells grown in rich medium required an increased amount of exogenous 5-aminolevulinic acid (ALA) for normal growth, as compared with cells grown in poor medium. Second, H500 cells grown with an insufficient supply of ALA had a prolonged lag phase but relatively normal growth during the logarithmic phase. An increased requirement of exogenous ALA in rich media was due to an impermeability of-the cells to ALA, resulting in a reduced ability to synthesize porphyrins. The latter could be also explained by change in permeability that was repressed under heme-deficient conditions.