Molecular basis for structural diversity in the core regions of the lipopolysaccharides of Escherichia coli and Salmonella enterica

Abstract

SummaryBacterial lipopolysaccharides (LPS) are unique and complex glycolipids that provide characteristic components of the outer membranes of Gram-negative bacteria. In LPS of the Enterobacteriaceae, the core oligosaccharide links a highly conserved lipid A to the antigenic O-polysaccharide. Structural diversity in the core oligosaccharide is limited by the constraints imposed by its essential role in outer membrane stability and provides a contrast to the hypervariable O-antigen. The genetics of core oligosaccharide biosynthesis in Salmonella and Escherichia coli K-12 have served as prototypes for studies on the LPS and lipo-oligosaccharides from a growing range of bacteria. However, despite the wealth of knowledge, there remains a number of unanswered questions, and direct experimental data are not yet available to define the precise mechanism of action of many gene products. Here we present a comparative analysis of the recently completed sequences of the major core oligosaccharide biosynthesis gene clusters from the five known core types in E. coli and the Ra core type of Salmonella enterica serovar Typhimurium and discuss advances in the understanding of the related biosynthetic pathways. Differences in these clusters reflect important structural variations in the outer core oligosaccharides and provide a basis for ascribing functions to the genes in these model clusters, whereas highly conserved regions within these clusters suggest a critical and unalterable function for the inner region of the core.

A novel strategy to isolate cell-envelope mutants resistant to phage infection: bacteriophage mEp213 requires lipopolysaccharides in addition to FhuA to enter Escherichia coli K-12

“…All of the mutants resistant to phage infection that we selected were related to the cell envelope. We confirmed that FhuA is the OM receptor, and we additionally found that the waaC and gmhD (earlier named rfaC and rfaD; Heinrichs et al, 1998) gene products are involved in phage infection.…”

Production of serum antibodies that recognise epitopes located on the R3 region of Escherichia coli core lipopolysaccharides by patients infected with strains of enterohaemorrhagic E. coli

“…[29]. However, as patients' serum antibodies binding to EHEC LPS did not bind to the core of S. Urbana, this moiety of the core was not thought to be involved in antibody binding.…”

“…The R1, R2, R3, R4 and K-12 LPS core structures have been partially elucidated [17,29] and strains of E. coli with R3 core share an inner core sugar -3-deoxy-Dmanno-oct-2-ulsonic acid (Kdo) -with strains of Salmonella spp. [29].…”

The Edwardsiella ictaluri O polysaccharide biosynthesis gene cluster and the role of O polysaccharide in resistance to normal catfish serum and catfish neutrophils

“…One of the enzymes to which it is most similar is a galactosyltransferase (WaaX) responsible for addition of Gal in a b-1,4 configuration in the R4 subtype of E. coli COS (Heinrichs et al, 1998a). WaaX is a member of a family of b-glycosyltransferases that contains conserved motifs within the N-terminal 100 amino acids (Heinrichs et al, 1998b).…”