The 718,122 base pair (bp) sequence of the Escherichia coli K-12 genome corresponding to the region from 12.7 to 28.0 minutes on the genetic map is described. This region contains at least 682 potential open reading frames, of which 278 (41%) have been previously identified, 147 (22%) were homologous to other known genes, 138 (20%) are identical or similar to the hypothetical genes registered in databases, and the remaining 119 (17%) did not show a significant similarity to any other gene. In this region, we assigned a cluster of cit genes encoding multienzyme citrate lyase, two clusters of fimbrial genes and a set of lysogenic phage genes encoding integrase, excisionase and repressor in the e14 genetic element. In addition, a new valine tRNA gene, designated valZ , and a family of long directly repeated sequences, LDR-A, -B and -C, were found.