ANALYSIS OF THE ESCHERICHIA-COLI GENOME .5. DNA-SEQUENCE OF THE REGION FROM 76.0-MINUTES TO 81.5-MINUTES

The DNA sequence of a 225.4 kilobase segment of the Escherichia coil K -12 genome is described here, from 76.0 to 81.5 minutes on the genetic map. This brings the total of contiguous sequence from the E.coli gen ome project to 725.1 kb(76.0 to 92.8 minutes). We found 191 putative c oding genes (ORFs) of which 72 genes were previously known, and 110 of which remain unidentified despite literature and similarity searches. Seven new genes-arsE, arsF, arsG, treF, xylR, xylG, and xylH-were ide ntified as well as the previously mapped pit and dctA genes. The arran gement of proposed genes relative to possible promoters and terminator s suggests 90 potential transcription units. Other features include 19 REP elements, 95 computer-predicted bends, 50 Chi sites, and one grey hole. Thirty-one putative signal peptides were found, including those of thirteen known membrane or periplasmic proteins. One tRNA gene (pr oK) and two insertion sequences (IS5 and IS150) are located in this se gment. The genes in this region are organized with equal numbers orien ted with or against replication.