Structural Study and Conformational Behavior of the Two DifferentLipopolysaccharide O-Antigens Produced by the Cystic Fibrosis Pathogen Burkholderia multivorans

Lipopolysaccharides (LPSs) are virulence factors expressed byGram-negative bacteria; they are among those mainly responsible for bacterial virulence. In this work we define the primary structure and the conformational features of the O-chain from the LPS produced by the highly virulent clinical isolate Burkholderiamultivorans strain C1576, an opportunistic human pathogen isolated in a cystic fibrosis center and causative of an outbreak with lethal outcome. We demonstrate that the LPS from thisclinical isolate consists of two O-polysaccharide chains present in different amounts and made up of repeating units, both containing deoxy sugar. Additionally, conformational studies have been performed to establish and compare the spatial arrangements of the two polysaccharides and differences in their shape have been highlighted. The comprehension of the structural and conformational features of the two repeating units may help to explain their biological significance, the molecular shape of the bacterial external surface, and the comprehension at the molecular level of the recognition mechanisms of the antibodies.