Coordinate regulation by iron of the synthesis of phenolate compounds and three outer membrane proteins in Escherichia coli

The biosynthesis of the low-molecular-weight iron carrier enterochelin and of three outer membrane polypeptides appears to be coordinately regulated by the amount of cell-associated iron in Escherichia coli K-12. Measurements of iron acquisition made throughout the growth cycle in iron-deficient media indicate that a very rapid accumulation of iron occurs in the first 2 h of growth; there is comparatively little iron uptake during exponential growth, which results in a gradual decrease in the cellular iron content with each generation. When this level falls below 400 ng of iron per mg (dry weight) of cells, there is a simultaneous onset of synthesis of the three outer membrane polypeptides and of enterochelin. This coordinate regulation was also observed in cells able to transport iron actively using only citrate as an iron-carrier.