title: Molecular cloning and expression in Escherichia coli K-12 of chromosomal genes determining the O7 lipopolysaccharide antigen of a human invasive strain of E. coli O7:K1.
abstract: We have cloned and studied the expression in Escherichia coli K-12 of chromosomal rfb genes determining the biosynthesis of the O7 lipopolysaccharide (LPS) antigen from E. coli K1 strain VW187. Two E. coli K-12 strains carrying recombinant cosmids gave positive coagglutination reactions with protein A-rich staphylococcal particles bearing an O7-specific rabbit polyclonal antiserum. Silver-stained polyacrylamide gels of total membranes extracted with hot phenol showed O side chain material which had O7 specificity as determined by immunoblotting experiments. However, the amount of O7 LPS expressed in E. coli K-12 was considerably lower than that produced by the wild-type strain VW187. Deletion and transposition experiments identified a region of about 17 kilobase pairs which is essential for the expression of O7 LPS. The existence of homologies between the O7 LPS genes and other E. coli O side chain genes was investigated by Southern blot hybridization experiments. An O7-specific probe fragment of 15 kilobase pairs did not hybridize to genomic DNA digests of E. coli strains belonging to several different O types, demonstrating that the O7 LPS genes are unique.
authors.affiliation: Department of Microbiology and Immunology, Oregon Health Sciences University, Portland 97201.
authors.forename: M A
authors.initials: MA
authors.lastname: Valvano
authors.forename: J H
authors.initials: JH
authors.lastname: Crosa
mesh_terms: D000942:Antigens, Bacterial / Q000235:genetics*; D015139:Blotting, Southern; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics* / Q000472:pathogenicity; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D008040:Genetic Linkage; D008070:Lipopolysaccharides / Q000235:genetics*; D015183:Restriction Mapping; D018805:Sepsis / Q000382:microbiology; D013045:Species Specificity
chemical_list: D000942:Antigens, Bacterial; D008070:Lipopolysaccharides