The structure of the O-polysaccharide isolated from pectinolytic gram-negative bacterium Dickeya aquatica IFB0154 is different from the O-polysaccharides of other Dickeya species

The species Dickeya aquatica was established in 2014 after the genomic characterization of the pectinolytic bacteria isolated from water. It was demonstrated that D. aquatica was able to cause symptoms of soft rot on the fruit of tomato and cucumber. According to earlier works, lipopolysaccharides are regarded as an important virulence factor of Pectobacteriaceae. An O-specific polysaccharide containing d-Fuc and l-Rha was obtained by mild acid hydrolysis of the lipopolysaccharide of D. aquatica IFB0154 (strain Dw044 isolated in Finland). By means of compositional analyses and NMR spectroscopy, the chemical repeating unit of the polymer was identified as a linear disaccharide of the structure shown below. The rhamnose residue was partially acetylated at O-2 or O-3. OAc (~40%) ↓₂ →3)-α-d-Fucp-(1 → 4)-α-l-Rhap-(1→ ↑³ OAc (~30%) The O-polysaccharides isolated from Dickeya dianthicola IFB0485 and Dickeya zeae IPO946 have a different structure, identical to that previously described for several strains of Dickeya solani and Dickeya dadantii 3937.