Mutants of Escherichia coli K-12 blocked in each of the three enzymatic reactions between chorismate and 2,3-dihydroxybenzoate, in the pathway leading to the iron-sequestering compound enterochelin, have been isolated and biochemically characterized. The three genes concerned (designated entA, entB and entC) have been shown to be clustered on the chromosome between purE and gal and to be located near minute 14 by cotransduction with the purE, lip, and fep genes. entA, entB, and entC were shown to be the structural genes for 2,3-dihydro-2,3-dihydroxybenzoate dehydrogenase, 2,3-dihydro-2,3-dihydroxybenzoate synthetase, and isochorismate synthetase, respectively.