Analysis of a cell division gene cluster in "Escherichia coli"

Abstract

Several genes, essential for cell growth and division in Escherichia coli, have been mapped to the 76 minute region of the chromosome. DNA sequencing of part of this region revealed three cell division genes (ftsY, ftsE, and ftsX) in a putative operon. A fourth gene (orf4) was also identified that was transcribed in the opposite direction to the putative operon. The genes rpof, f am, dnaM and ftsS have also been mapped to this region, but their location, relative to the putative operon, was unknown. In this study the fam and rpoU genes were independently cloned and shown to be allelic. The dnaM gene was also found to be an allele of rpoH, and the gene was found to lie immediately downstream of the putative cell division operon. The restriction map of the area was extended, and the distance between the putative operon and the nearest known gene clockwise on the chromosome map (pit), was determined. The ftsS gene was found to be an allele of ftsX. Two promoters were identified within the putative operon, one proximal to ftsY and the other proximal to ftsE. A combination of S1 and primer extension mapping, of the mRNA transcripts, identified the transcriptional start sites of these two promoters. A polycistronic message was also identified encoding all three cell division genes, suggesting at least some degree of co-ordinated expression. In conclusion, the transcriptional organisation of the 76 minute, essential gene cluster has been determined, and evidence has been presented. that there is some degree of co-ordinated expression of the component genes