Legionaminic acid

OPS of Acinetobacter baumannii 024 (23) is a heteropolysaccharide that contains a 5-tV-acetyl derivative of legionaminic acid in about half of its tetrasaccharide repeating units and a S-iV-IXXi-S-hydroxybutanoyl] derivative in the remaining units35 (Fig. 6). 

Fig. 6. Structures of the LPS-derived oligosaccharides and OPS containing legionaminic acid (Leg). [D-a-D-Hep and L-a-D-Hep, D-glycero- and L-glycero-a-D-manno-heptose Kdo, 3-deoxy-D-manno-oct-2-ulosonic acid Fuc4NR3Hb, 4-[(R)-3-hydroxybutanamido]-4,6-dideoxygalactose Ala, L-alanyl Cm, carbamoyl PEtn, ethanolamine phosphate R is acetyl in some repeating units and (S)-3-hydroxybutanoyl in the others.]...

Based on these findings, it is likely that ORFs 23, 24, and 25 encode enzymes that play a role in biosynthesis and polymerization of legionaminic acid and that the biosynthetic pathway is similar to that of bacterial sialic acid-containing polysaccharides.1 ORFs that encode putative legionaminic acid transferase or polymerase were not found in the 32.6-kb locus. 

The 8-O-acetyl-associated epitope of legionaminic acid was also found in P. fluorescens ATCC 49271, which has the same OPS structure 17 as L. pneumophila serogroup l32,56 (Fig. 5). This epitope, possibly along with other, yet uncharacterized cross-reactive epitopes, is likely responsible for the serological cross-reactivity exhibited by P. fluorescens and distantly related L. pneumophila. 

---