The galE gene of Campylobacter jejuni is involved in lipopolysaccharide synthesis and virulence

Lipopolysaccharide (LPS) is one of the main virulence factors of gram-negat ive bacteria. The LPS from Campylobacter spp, has endotoxic properties and has been showm to play a role in adhesion. We previously cloned a gene clus ter (wla) which is involved in the synthesis of the Campylobacter jejuni 81 116 LPS molecule. Sequence alignment of the first gene in this cluster indi cated similarity with galE genes. These genes encode a UDP-glucose 4-epimer ase, 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 stra ins 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 tha t 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 molec ular weight that did not react with antiserum raised against the parental s train. These results show an essential role for the galE gene in the synthe sis of C. jejuni LPS. The galE mutant also showed a reduction in its abilit y to adhere to and invade INT407 cells. However, it was still able to colon ize chickens to the same level as the wild-type strain. The serum resistanc e and hemolytic activity of this mutant were not changed compared to the pa rent strain. The ability of the mutant to take up DNA and integrate it in i ts genome was reduced 20-fold. These results show that LPS of C. jejuni is an important virulence factor.