Novel features in the structure and new insights in the biosynthesis of the lipopolysaccharide of Brucella

ROMANI A; COUTO AS; CASABUONO AC; UGALDE JE; DEL GIUDICE MG; CZIBENER C

Chicago

Conferencia; 71 th Annual Brucellosis research conference; 2018

International Brucellosis Society

Lipopolysaccharide (LPS) is the mayor outer membrane antigen in gram-negative bacteria and, in pathogens, is a central macromolecule in the pathogenic process. In Brucella the LPS has been shown to be a virulence factor required for the successful establishment of a persistent infection and that it affects the efficient intracellular replication of the bacterium, a hallmark of the infectious cycle. Despite we have a great body of knowledge regarding the structure and biosynthesis of the LPS in Brucella there are still several aspects of the mechanisms involved in its synthesis that remain unsolved. In this presentation we revisit several aspects of the structure of the LPS and add new insights into the mechanisms involved in its biosynthesis. By performing a MADITOF-MS/MS analysis of highly purified LPS, we found a new feature in the lipid A: a pyrophosphorylethalomine substituting the backbone. LID-MS/MS analysis of some of the detected ions indicated that the lipid A structure composed by the diGlcN3N disaccharide is mainly hexa and penta-acylated, bearing one phosphate and one pyrophosphorylethanolamine residue. We have additionally identified and characterized the lipid-intermediate in the O-antigen biosynthesis and surprisingly found that is a decranyl phosphate instead of the more common undecaprenyl phosphate utilized by gram-negative bacteria. The generation and characterization of mutants in genes with no known function has allowed us to propose a model for the chain length control of the O-antigen in Brucella that does not fit the canonical models for homopolymeric LPS known to date.