Figure 4. Effect of deletion of LPS-modifying enzymes on Salmonella-mediated killing of G. mellonella.

Survival of G. mellonella was assessed after injection of 4 × 10⁴ S. Typhimurium NCTC 12023 WT or mutant derivatives lacking different LPS-modifying regulators and enzymes. (A) Comparison of WT with mutant strain MvP724, which lacks the regulators of gene expression wzz _ST /wzz _fepE. For complementation purposes, plasmid p3390 was transformed into MvP724, from which both wzz _ST and wzz _fepE were expressed under control of the wzz _ST promoter. Plasmid pWSK29 was transformed into the mutant strain as a vector-only control. (B) Impact of the O-antigen ligase, WaaL, on bacterial-mediated killing of G. mellonella larvae. Infection by the ΔwaaL mutant MvP1036, with or without the empty vector (pWSK29), and its complemented derivative MvP1036 (p3313), was performed alongside WT injection at a total amount of 4 × 10⁴ bacteria per larvae. PBS: buffer control. Data as shown are the representative results of three independent experiments, for which similar outcomes were obtained.