title: Distribution of the rol gene encoding the regulator of lipopolysaccharide O-chain length in Escherichia coli and its influence on the expression of group I capsular K antigens.
abstract: The rol (cld) gene encodes a protein involved in the expression of lipopolysaccharides in some members of the family Enterobacteriaceae. Rol interacts with one or more components of Rfc-dependent O-antigen biosynthetic complexes to regulate the chain length of lipopolysaccharide O antigens. The Rfc-Rol-dependent pathway for O-antigen synthesis is found in strains with heteropolysaccharide O antigens, and, consistent with this association, rol-homologous sequences were detected in chromosomal DNAs from 17 different serotypes with heteropolysaccharide O antigens. Homopolymer O antigens are synthesized by a pathway that does not involve either Rfc or Rol. It was therefore unexpected when a survey of Escherichia coli strains possessing mannose homopolymer O8 and O9 antigens showed that some strains contained rol. All 11 rol-positive strains coexpressed a group IB capsular K antigen with the O8 or O9 antigen. In contrast, 12 rol-negative strains all produced group IA K antigens in addition to the homopolymer O antigen. Previous research from this and other laboratories has shown that portions of the group I K antigens are attached to lipopolysaccharide lipid A-core, in a form that we have designated K(LPS). By constructing a hybrid strain with a deep rough rfa defect, it was shown that the K40 (group IB) K(LPS) antigen exists primarily as long chains. However, a significant amount of K40 antigen was surface expressed in a lipid A-core-independent pathway. The typical chain length distribution of the K40 antigen was altered by introduction of multicopy rol, suggesting that the K40 group IB K antigen is equivalent to a Rol-dependent O antigen. The prototype K30 (group IA) K antigen is expressed as short oligosaccharides (primarily single repeat units) in K(LPS), as well as a high-molecular-weight lipid A-core-independent form. Introduction of multicopy rol into the K30 strain generated a novel modal pattern of K(LPS) with longer polysaccharide chains. Collectively, these results suggested that group IA K(LPS) is also synthesized by a Rol-dependent pathway and that the typically short oligosaccharide K(LPS) results from the absence of Rol activity in these strains.
authors.affiliation: Department of Microbiology, University of Guelph, Guelph, Ontario, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Dodgson
authors.forename: P
authors.initials: P
authors.lastname: Amor
authors.forename: C
authors.initials: C
authors.lastname: Whitfield
mesh_terms: D000942:Antigens, Bacterial / Q000096:biosynthesis / Q000235:genetics*; D016667:Bacterial Capsules / Q000096:biosynthesis / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D017931:DNA Primers; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D050356:Lipid Metabolism; D008969:Molecular Sequence Data; D019081:O Antigens / Q000378:metabolism; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D017931:DNA Primers; D029968:Escherichia coli Proteins; D019081:O Antigens; D011135:Polysaccharides, Bacterial; C036962:capsular polysaccharide K1; C489586:wzzB protein, E coli; C075969:rol protein, Bacteria