2-Hydroxylation of Acinetobacter baumannii Lipid A Contributes to Virulence

causes a wide range of nosocomial infections. This pathogen is considered a threat to human health due to the increasingly frequent isolation of multidrug-resistant strains. There is a major gap in knowledge on the infection biology of , and only a few virulence factors have been characterized, including lipopolysaccharide. The lipid A expressed by is hepta-acylated and contains 2-hydroxylaurate. The late acyltransferases controlling the acylation of lipid A have been already characterized. Here, we report the characterization of LpxO, which encodes the enzyme responsible for the 2-hydroxylation of lipid A. By genetic methods and mass spectrometry, we demonstrate that LpxO catalyzes the 2-hydroxylation of the laurate transferred by LpxL. LpxO-dependent lipid A 2-hydroxylation protects from polymyxin B, colistin, and human β-defensin 3. LpxO contributes to the survival of in human whole blood and is required for pathogen survival in the waxmoth LpxO also protects from antimicrobial peptides and limits their expression. Further demonstrating the importance of LpxO-dependent modification in immune evasion, 2-hydroxylation of lipid A limits the activation of the mitogen-activated protein kinase Jun N-terminal protein kinase to attenuate inflammatory responses. In addition, LpxO-controlled lipid A modification mediates the production of the anti-inflammatory cytokine interleukin-10 (IL-10) via the activation of the transcriptional factor CREB. IL-10 in turn limits the production of inflammatory cytokines following infection. Altogether, our studies suggest that LpxO is a candidate for the development of anti- drugs.