Related structures of the O-polysaccharides of Cronobacter dublinensis G3983 and G3977 containing 3-(N-acetyl-L-alanyl)amino-3,6-dideoxy-D-galactose

Cronobacter spp. are emerging opportunistic human pathogens linked with life-threatening infections predominantly in neonates. O-Antigen (O-polysaccharide) is highly variable and plays an important role in virulence and niche adaptation. In this work, short-chain O-polysaccharides consisting on the average of 2-3 repeating units were obtained by mild acid or mild alkaline degradation of the lipopolysaccharides of C. dublinensis G3983 and G3977 and studied by composition analysis, Smith degradation, and (1)H and (13)C NMR spectroscopy. The following structures of the O-polysaccharides were established: [Formula: see text] where R indicates H in strain G3983 or α-D-Glcp in strain G3977, d-Fuc3NAlaAc indicates 3-(N-acetyl-L-alanyl)amino-3,6-dideoxy-D-galactose. Both strains share the O-antigen gene cluster, which is identical to that of C. dublinensis O1 (Foodborne Pathog. Dis.2013, 10, 343-352). The assigned gene functions are in agreement with the O-antigen structure of C. dublinensis G3983, and the side-chain glucosylation of the O-antigen of C. dublinensis G3977 is evidently encoded elsewhere in the genome.