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. 2021 Aug 31;12:725383. doi: 10.3389/fmicb.2021.725383

Figure 1.

Figure 1

Representative mass spectra of susceptible and modified Pseudomonas aeruginosa lipid A acquired using the linear negative-ion mode of a matrix-assisted laser desorption ionization (MALDI) Biotyper Sirius system (Bruker Daltonics). (A) Susceptible P. aeruginosa PAO1 lipid A is detected as two major peaks at m/z 1,446.7 and m/z 1,462.7. (B) Lipid A from mutant pmrB (AB8.2) with additional peaks at m/z 1,577.9, m/z 1,593.9, m/z 1,708.9, and m/z 1,724.9 corresponding to 4-amino-L-arabinose (L-Ara4N) addition on the penta-acylated lipid A (peaks at m/z m/z 1,446.7 and m/z 1,462.7). (C) Lipid A from colistin-resistant P. aeruginosa clinical isolates is modified by L-Ara4N, which are detected as additional peaks at m/z 1,577.9, m/z 1,593.9. (D) Diagram of P. aeruginosa lipid A at m/z 1,446.7. (E) Diagram of P. aeruginosa lipid A at m/z 1,577.9. L-Ara4N residue is shown in red. (F) Diagram of P. aeruginosa lipid A at m/z 1,708.9. L-Ara4N residues are shown in red.