ABSTRACT
Brucella lipopolysaccharide (LPS) is one of the key molecules involved in Brucella virulence. Despite this, its structure has not been fully elucidated. In this chapter the LPS structure will be reviewed in the light of structural and genomic comparisons, with emphasis on the core and lipid A sections. The Brucella genome contains homologues of the ORFs necessary to synthesise lipid IV A and to acylate it with long-chain fatty acids. Despite the overall similarity with R. leguminosarum, the only homologue to those that modify the disaccharide backbone of the latter is a putative phosphatase which may act at position 1 to generate monophosphoryl lipid A. The comparisons support the absence of heptose, galacturonic acid and phosphate in the core, or of arabinosamine in lipid A. An ORF putatively involved in phosphoethanolamine transfer was found in B. melitensis and B. suis but carried a missense mutation in B. abortus, suggesting species differences. The evidence supports the hypothesis that Brucella is unique among α-Proteobacteria in that the lipopolysaccharide core lacks all negatively charged groups but 3-deoxy-D-manno-2-octulosonic acid while keeping amino-compounds. It is postulated that this reduced negative charge plus the presence of long chain fatty acids are the basis for the altered pathogen-associated molecular pattern of Brucella lipopolysaccharide.
