The galE Gene of Campylobacter jejuni Is Involved in Lipopolysaccharide Synthesis and Virulence

Abstract

Lipopolysaccharide (LPS) is one of the main virulence factors of gram-negative bacteria. The LPS fromCampylobacter spp. has endotoxic properties and has been shown to play a role in adhesion. We previously cloned a gene cluster (wla) which is involved in the synthesis of the Campylobacter jejuni 81116 LPS molecule. Sequence alignment of the first gene in this cluster indicated similarity with galE genes. These genes encode a UDP-glucose 4-epimerase, which catalyzes the interconversion of UDP-galactose and UDP-glucose. A Salmonella galE mutant was transformed with the galE gene from C. jejuni. The LPS analysis of wild-type, galE, and complemented galE Salmonella strains showed that the C. jejuni galE gene could restore the smooth wild-type Salmonella LPS. A UDP-glucose 4-epimerase assay was used to demonstrate that the galE gene from C. jejuni encoded this epimerase. We constructed a C. jejuni galE mutant which expressed a lipid A-core molecule of reduced molecular weight that did not react with antiserum raised against the parental strain. These results show an essential role for the galE gene in the synthesis of C. jejuni LPS. The galE mutant also showed a reduction in its ability to adhere to and invade INT407 cells. However, it was still able to colonize chickens to the same level as the wild-type strain. The serum resistance and hemolytic activity of this mutant were not changed compared to the parent strain. The ability of the mutant to take up DNA and integrate it in its genome was reduced 20-fold. These results show that LPS of C. jejuni is an important virulence factor.

A Single Bifunctional UDP-GlcNAc/Glc 4-Epimerase Supports the Synthesis of Three Cell Surface Glycoconjugates in Campylobacter jejuni

“…Fry et al (12) reported that the lipid A-core LOS from a galE mutant of C. jejuni was smaller than that of the parental strain, which is in perfect agreement with the data presented in this report. The GalE enzyme of C. jejuni 81116 identified and characterized by Fry et al (11,12) is most likely a Gne enzyme, considering it is almost identical to Gne from C. jejuni NCTC 11168. In addition, the amino acid residues of the C. jejuni 81116 GalE predicted to constitute the UDP sugarbinding site are the same as those of the C. jejuni NCTC 11168 Gne (aa residues numbered 1-6 in Fig.…”

“…4A, trace C). These data indicated that GalE from C. jejuni NCTC 11168 epimerized UDP-Glc into UDP-Gal, as does GalE from C. jejuni 81116 (12).…”

Molecular Characterization of Invasive and Noninvasive Campylobacter jejuni and Campylobacter coli Isolates

“…The fact that some invasive strains also were not identified by PCR supports the existence of important polymorphism and high heterogeneity in the iam locus or suggests that there may be other genetic markers of invasion in different loci. In previous studies on the molecular characterization of genes associated with the phenotype of adherence to and invasion of epithelial cells, several Campylobacter strains have been studied and some genetic loci have been identified: peb1 (26), peb4A (3), cadF (15), and fla (13,34), and more recently the gene that encodes antigen B (16) and the galE gene, involved in lipopolysaccharide synthesis and virulence (8).…”

Ganglioside Molecular Mimicry and Its Pathological Roles in Guillain-Barré Syndrome and Related Diseases

“…Strains possessing this locus are known to produce sialylated outer core structures that mimic host gangliosides and have been implicated in triggering the onset of GBS. Fry et al (19) reported that the C. jejuni 81116 galE gene encoding a UDP-galactose-4-epimerase, which catalyzes interconversion of UDP-galactose and UDP-glucose, is indispensable to synthesizing ganglioside-like structures of the LOS core oligosaccharide. Recently, Shu et al (73) performed immunization experiments in guinea pig models using C. jejuni HB9313 (HS: 19) and its galE mutant and showed a high titer of anti-GM1 IgG and axonal degeneration in animals sensitized with HB9313, but there was no GM1 antibody titer and no significant morphological change of the sciatic nerve of animals sensitized with the galE mutant ( Table 2).…”