FIGURE 9.

Multicopy suppression leading to addition of l-Ara4N in the LPS of mutant synthesizing tetraacylated lipid A. Charge deconvoluted ES FT-ICR mass spectra in negative ion mode of native LPS of strain SR7781 Δ(lpxL lpxM lpxP) (A) and SR7781/pmsbA⁺ (B). Cultures were grown in 121 medium at 30 °C and LPS was extracted. Mass numbers refer to monoisotopic peaks with predicted composition, correlating with varying numbers of the substitution of P-EtN and/or l-Ara4N on the basic structure lipid IV_A-3Kdo-Rha with 3Hep-3Hex are presented in bold. The mass numbers in italics and underlined in panel B refer to species corresponding to tetraacylated derivatives of glycoform II with 2 Kdo residues (35, 36), but with varying P-EtN and/or l-Ara4N substitutions. Both the spectra for panels A and B were recoded under the same conditions. In panel B accumulation of various intermediates with various substitutions following MsbA overexpression is depicted.