Structure and genetics of the O-antigen of Cronobacter sakazakii G2726 (serotype O3) closely related to the O-antigen of C. muytjensii 3270.

The O-specific polysaccharide (O-antigen) was isolated from the lipopolysaccharide of Cronobacter sakazakii G2726 (serotype O3) and studied by sugar analysis, Smith degradation, and (1)H and (13)C NMR spectroscopy. The following structure of the acidic O-polysaccharide was established: [structure: see text]. This structure is closely related to that of the O-polysaccharide of Cronobacter muytjensii 3270, which has the same main chain and differs only in the lack of glucosylation. The O-antigen gene cluster of C. sakazakii G2726 found between the gnd and galF genes was sequenced, and the gene functions were tentatively assigned by similarity to related genes from available databases and taking into account the O-polysaccharide structure.

Elucidation of the structure and characterization of the gene cluster of the O-antigen of Cronobacter sakazakii G2592, the reference strain of C. sakazakii O7 serotype.

The O-specific polysaccharide from the lipopolysaccharide of Cronobacter sakazakii G2592 was studied by sugar analysis along with 1D and 2D (1)H and (13)C NMR spectroscopy, and the following structure of the pentasaccharide repeating unit was established: [See figure in text]. This structure is unique among the known bacterial polysaccharide structures, which is in accord with classification of strain G2592 into a new C. sakazakii serotype, O7. It is in agreement with the O-antigen gene cluster of this strain, which was found between the housekeeping genes JUMPStart and gnd and characterized by sequencing and tentative assignment of the gene functions.