Figure 6. MALDI-TOF spectra of purified lipid A produced by arnT mutants.

∆arnT denotes strain MH55 (∆arnT-arnBC⁺ lptG^S), which carries a lptG suppressor mutation (Table S1). Plasmids encoding ArnT proteins with various replacements are introduced into MH55 by triparental mating. The profiles represented were obtained using the negative ion mode. I-II Tetra-acylated lipid A with one or two phosphates molecules; III-IV, Tetra-acylated lipid A with one or two l-Ara4N molecules. V, Penta-acylated lipid A; VI-VII, Penta-acylated lipid A with one or two l-Ara4N molecules.