Production of enterochelin by Escherichia coli 0111.

The major neutral iron-transporting compound produced by Escherichia coli 0111/K58/H2 has been isolated from iron-deficient cultures of the organism and compared with the corresponding compound, enterochelin, produced by E. coli K12. The product contained serine and 2,3-dihydroxybenzoic acid and formed a complex with Fe3+. Since the PMR spectra of the products from the two strains were identical, it was concluded that E. coli 0111 also secreted enterochelin under iron-deficient conditions. Although it was not possible to establish the optical configuration of the serine residues in the molecule, the CD spectra of the metal free and Fe3+, complexes were found to be of the same sign and magnitude. The spectra show that metal binding results in considerable conformational changes in the enterochelin molecule. The biological properties of the two compounds appear to be identical as judged by their ability to abolish the bacteriostatic effect of serum on E. coli 0111.