A chronic strain of the cystic fibrosis pathogen Pandoraea pulmonicola expresses a heterogenous hypo-acylated lipid A

Pandoraea sp. is an emerging Gram-negative pathogen in cystic fibrosis causing severe and persistent inflammation and damage of the lungs. The molecular mechanisms underlying the high pathogenicity of Pandoraea species are still largely unknown. As Gram-negatives, Pandoraea sp. express lipopolysaccharides (LPS) whose recognition by the host immune system triggers an inflammatory response aimed at the bacterial eradication from the infected tissues. The degree of the inflammatory response strongly relies on the fine structure of the LPS and, in particular, of its glycolipid moiety, i.e. the lipid A. Here we report the structure of the lipid A isolated from the LPS of a chronic strain of P. pulmonicola (RL 8228), one of the most virulent identified so far among the Pandoraea species. Our data demonstrated that the examined chronic strain produces a smooth-type LPS with a complex mixture of hypoacylated lipid A species displaying, among other uncommon characteristics, the 2-hydroxylation of some of the acyl chains and the substitution by an additional glucosamine on one or both the phosphate groups.