Immunochemical studies on R mutants of Yersinia enterocolitica O:3

Three mutants of Yersinia enterocolitica O:3, namely: YeO3-R1, YeO3-RfbR7 and YeO3-c-trs8-R were classified on the basis of sodium dodecyl sulphate/polyacrylamide gel electrophoresis (SDS/PAGE) profile of isolated lipopolysaccharides (LPS) as belonging to the Ra- (the first) and the Re-type (the other two mutants). Methylation analysis, in addition to C-13 and H-1 NMR studies of purified core oligosaccharides revealed structures similar to those established previously for the full core of Y. enterocolitica O:3 in the case of the Ra mutant, and identical to that reported for the Re mutant Ye75R, in the case of the two other mutants. The O-specific sugar, 6d-L-altrose, which forms a homopolymeric O-chain, was present in small amounts in all three LPS preparations, as well as in the core oligosaccharide preparations along with the Ra and the Re sugars, characteristic of the Y. enterocolitica O:3 core. This result is in line with genetic data, indicating that it is the inner core region which is the receptor for the O-specific chain in Y. enterocolitica O:3. This region seems likewise to be the anchoring region for the enterobacterial common antigen (ECA), as shown by SDS/PAGE/Western blot analysis with monoclonal antibodies against EGA. In addition, we also demonstrated that the Ye75R mutant Re and its parental strain Ye75S, both were ECA-immunogenic strains. So far, ECA-immunogenic strains, i.e. those with LPS-linked EGA, were only identified in E. coli mutants of the R1, R4 and K-12 serotype.