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

Abstract

The biosynthesis of the low MW Fe carrier enterochelin and of 3 outer membrane polypeptides appears to be coordinately regulated by the amount of cell-associated Fe in E. coli K-12. Measurements of Fe acquisition made throughout the growth cycle in Fe-deficient media indicate that a very rapid accumulation of Fe occurs in the first 2 h of growth; there is comparatively little Fe uptake during exponential growth, which results in a gradual decrease in the cellular Fe content with each generation. When this level falls below 400 ng of Fe/mg (dry wt) of cells, there is a simultaneous onset of synthesis of the 3 outer membrane polypeptides and of enterochelin. This coordinate regulation was also observed in cells able to transport Fe actively using only citrate as an Fe-carrier.