Fig. S6.

Overexpression of VexE does not affect cell growth or lipid A structure in E. coli. (A) Viable cell count growth curves of E. coli Top10 harboring plasmids encoding VexE and VexE^H466A. Overexpression of VexE, induced by the addition of l-arabinose [final concentration 0.02% (wt/vol)] at 2.5 h (arrow), slightly hindered growth of E. coli, independently of catalytic activity, because a similar profile was obtained with VexE^H466A. Data represent the mean ± SE of three independent experiments. Light micrographs depict cells after 8.5 h growth. (Scale bars, 2 μm.) (B) ESI-MS of lipid A species isolated from E. coli BKT09, which possesses mutations in lpxL, lpxM, lpxP, and pagP and therefore produces only tetraacylated lipid A. Overexpression of the secondary acyltransferases LpxL and LpxM resulted in the expected addition of laurate and palmitate modifications, respectively, generating pentaacylated lipid A. Overexpression of VexE did not alter lipid A structure.