Fmt bypass in Pseudomonas aeruginosa causes induction of MexXY efflux pump expression

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Pathogenesis

Background:

• Pseudomonas aeruginosa exhibits intrinsic resistance to peptide deformylase inhibitors (PDF-Is).
• Efflux pumps, including MexAB-OprM and MexXY-OprM, play a significant role in this resistance.
• Understanding resistance mechanisms is crucial for developing effective antimicrobial therapies.

Purpose of the Study:

• To elucidate the mechanisms of intrinsic and acquired resistance of P. aeruginosa to PDF-I LBM415.
• To investigate the role of efflux pumps and specific gene mutations in PDF-I resistance.
• To explore the physiological function of the MexXY efflux pump in response to protein synthesis impairment.

Main Methods:

• Genetic manipulation of P. aeruginosa PAO1, including gene deletions (mexAB-oprM).
• Exposure to PDF-Is to select for resistant mutants.
• Identification of mutations in fmt and folD genes.
• Transcriptional profiling and promoter fusion analysis (mexX::lux) to assess gene expression.
• Complementation studies to confirm gene function.

Main Results:

• MexAB-OprM and MexXY-OprM efflux pumps mediate intrinsic resistance to LBM415, with MexXY being induced by the inhibitor.
• Mutants selected for resistance to PDF-Is utilized the MexCD-OprJ efflux pump.
• Mutations in fmt and folD genes conferred resistance by impairing protein synthesis, leading to upregulation of MexXY expression.
• fmt and folD mutations constitutively induced mexXY and PA5471 expression, which was reversed by complementation.

Conclusions:

• MexXY efflux pump has a physiological role in responding to impaired ribosome function or protein synthesis.
• fmt and folD mutations generate an intracellular signal that induces mexXY expression, contributing to PDF-I resistance.
• These findings provide insights into bacterial defense strategies against protein synthesis inhibitors and potential therapeutic targets.