P-186 - Lipid A remodeling in Pseudomonas species during environmental adaptation

Pathogens of the Pseudomonas syringae species complex (PSSC) infect many important crops worldwide and are key model organisms for studying pathogen- host interactions. They evade or suppress plant immunity and manipulate their hosts for nutrient acquisition. One well-known mechanism for evading host immunity in mammalian pathogens involves lipopolysaccharide modifications, the major constituent of Gram-negative bacterial cell walls, especially its lipid A (LA) moiety, e.g., modifications of acyl chains or primary phosphates. This LA remodeling contributes to maintaining an effective cell wall barrier in different environments. In silicoanalyses of PSSC strains, it was shown that LA biosynthetic enzymes are highly conserved, while only some known LA remodeling enzymes are present and less conserved. Mass spectrometric analysis of LA structures of selected PSSC strains and mutants of LA remodeling genes show that the LA modifications and causal enzymes are principally conserved. To study how LA remodeling aids PSSC adaptation to different environments, we monitor bacterial performance and LA structures under varying environmental conditions and nutrient availability. PSSC strains are cultured in full strength and different minimal media at different temperatures and pH levels in liquid or solid media. Our findings will help to explain the factors that trigger LA remodeling, shedding light on how these pathogens adapt to different environments, including variations in niche.