Participation of Acyl-Coenzyme A Synthetase FadD4 of PAO1 in Acyclic Terpene/Fatty Acid Assimilation and Virulence by Lipid A Modification.

The pathogenic bacterium possesses high metabolic versatility, with its effectiveness to cause infections likely due to its well-regulated genetic content. PAO1 has at least six paralogous genes, which have been implicated in fatty acid (FA) degradation and pathogenicity. In this study, we used mutagenesis and a functional approach in PAO1 to determine the roles of the gene in acyclic terpene (AT) and FA assimilation and on pathogenicity. The results indicate that encodes a terpenoyl-CoA synthetase utilized for AT and FA assimilation. Additionally, mutations in paralogs led to the modification of the quorum-sensing / systems, as well as the content of virulence factors pyocyanin, biofilm, rhamnolipids, lipopolysaccharides (LPS), and polyhydroxyalkanoates. In a pathogenicity model, culture supernatants from the 24-h-grown single mutant increased lethality compared to the PAO1 wild-type (WT) strain; however, the double mutants , , and and single mutant increased worm survival. A correlation analysis indicated an interaction between worm death by the PAO1 strain, the mutation, and the virulence factor LPS. Fatty acid methyl ester (FAME) analysis of LPS revealed that a proportion of the LPS and FA on lipid A were modified by the mutation, suggesting that FadD4 is also involved in the synthesis/degradation and modification of the lipid A component of LPS. LPS isolated from the mutant and double mutants and showed a differential behavior to induce an increase in body temperature in rats injected with LPS compared to the WT strain or from the and mutants. In agreement, LPS isolated from the mutant and double mutants and increased the induction of IL-8 in rat sera, but IL1-β cytokine levels decreased in the double mutants and . The results indicate that the genes are implicated in the degree of pathogenicity of PAO1 induced by LPS-lipid A, suggesting that FadD4 contributes to the removal of acyl-linked FA from LPS, rendering modification in its immunogenic response associated to Toll-like receptor TLR4. The genetic redundancy of is important for bacterial adaptability and pathogenicity over the host.