Abstract:Lipopolysaccharide (LPS), a key component on the outer side of the outer membrane (OM) of Gramnegative bacteria, is an important virulence factor affecting the characteristics of the outer cell membrane of pathogenic bacteria. However, at present, there is a lack of in-depth research on the pathogenic mechanism of bacterial LPS. In this study, differential lipidomic studies were carried out for the first time on the wild Escherichia coli strain W3110 and its LPS structural mutants ΔwaaC and Δ(lpxL lpxM lpxP), and the effects of LPS structural changes on lipidome. The results indicated that the loss of LPS-related structure in E. coli significantly altered the type and relative content of cell lipids, which was closely related to the change of OM characteristics. Compared with W3110, the permeability of ΔwaaC and Δ(lpxL lpxM lpxP) increased by 13.59% to 19.00%, and the fluidity of the OM decreased by 23.71% to 32.84%. Differential lipidomics revealed that 416 lipids of 22 subclasses were identified in W3110. The types of lipid species of the two mutant strains were reduced, while new lipids such as CL(14:0/14:0/15:0/12:0)-H, CL(17:3/15:0/12:0/14:0)-H, and CL(18:3/12:0/14:0/15:0)-H appeared in both mutants. In addition, most of the lipid contents of the two mutant strains changed significantly, in particular, the monounsaturated PE decreased by 3.07%~9.02%, and the monounsaturated CL increased by 1.11%~1.73%. There were also large differences in lipidome between ΔwaaC and Δ(lpxL lpxM lpxP). This study revealed that the structural changes of LPS resulted in significant alterations in lipid type and relative strength, which was an important factor for the change in the OM characteristics of E. coli.
