Genetic characterization of the O4 polysaccharide gene cluster from Escherichia coli

The Escherichia coli O4 serotype is among those commonly isolated from urinary tract infections. In order to study the genetics of the O-antigen, the O4 biosynthesis genes from a uropathogenic E. coli have previously been cloned into E. coli K-12. A subclone, GH58, has been identified which reacts with antisera against the O4 serotype. In contrast to the wild-type parental strain, lipopolysaccharide (LPS) from this clone is devoid of rhamnose and does not cross-react with O18 antisera. The recombinant plasmid from GH58, pGH58, was used to transform the rfb deletion strain HU1190. The resultant strain agglutinates in O4 antisera, but produces unpolymerized LPS. Escherichia coli K-12 strains HB101 and RC712 containing pGH58 produce polymerized LPS, indicating that the genetic background of the host can influence the LPS encoded by recombinant molecules. A cosmid, pGH84, has been identified which encompasses the entire pGH58 gene sequences and includes an additional 34 kilobases of DNA. HU1190 containing this cosmid agglutinates in O4 antisera and produces a polymerized LPS. By constructing several deletion subclones of pGH84, we have localized the genes necessary for polymerized LPS to a 5.5 kb ClaI-BamHI fragment. P1 transductants that make polymerized and unpolymerized O4 LPS have also been identified.