Work

Direct interaction between phosphotransferase LpxT and ArnT modulates polymyxin B resistance in Pseudomonas aeruginosa

Year: 2026

Type: article

Abstract: ABSTRACT Pseudomonas aeruginosa is a common human opportunistic pathogen that causes a variety of acute and chronic infections. Polymyxins are considered last-resort options for treating serious infections caused by multidrug-resistant gram-negative bacteria. Previously, we evolved PAO1 by serial passage in the presence of sublethal concentrations of polymyxin B, resulting in the polymyxin B-resistant strain PAO1-D14. In this study, we investigate the molecular mechanisms of resistance to polymyxin B in PAO1-D14. We found that the pmrB L189Q missense mutation results in a fourfold increase in the minimum inhibitory concentration (MIC), while deletion of lpxT , the phosphotransferase-encoding gene, confers an additional eightfold increase in the MIC of the pmrB L189Q strain but not in the wild-type PAO1 strain. Using 1-N-phenylnaphthylamine and Dansyl-polymyxin B binding assays, we observed that the lpxT mutation decreased the amount of polymyxin B bound to the bacterial surface and reduced membrane permeability in the pmrB L189Q mutant. A co-purification assay revealed an interaction between L-Ara4N transferase ArnT and LpxT. The amino acid-substituted version of LpxT G52AK137A lost the interaction with ArnT and no longer restored the polymyxin B resistance of pmrB L189Q Δ lpxT . Additionally, deletion of arnT in pmrB L189Q Δ lpxT restored susceptibility to polymyxin B to the levels seen in the pmrB L189Q strain. Collectively, our findings reveal a novel role for lpxT and its molecular mechanism to defend against polymyxin B in P. aeruginosa . IMPORTANCE Treatment of Pseudomonas aeruginosa infections is challenging due to its antibiotic resistance. Polymyxins are considered last-resort options for treating serious infections caused by multidrug-resistant P. aeruginosa . Understanding the molecular mechanisms of polymyxin resistance may provide clues for the development of new therapeutic strategies against P. aeruginosa . In this study, we demonstrated that the phosphatidic acid-phosphatase family (PAP2) protein LpxT interacts with L-Ara4N transferase ArnT and controls polymyxin B resistance in P. aeruginosa . Our findings reveal a novel role for lpxT and its molecular mechanism to defend against polymyxin B in P. aeruginosa .

Source: Microbiology Spectrum

DOI: 10.1128/spectrum.01852-25