Pseudomonas aeruginosa Oligoribonuclease Controls Tolerance to Polymyxin B by Regulating Pel Exopolysaccharide...

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Polymyxins are crucial last-resort antibiotics against multidrug-resistant Gram-negative bacteria.
• Pseudomonas aeruginosa, an opportunistic pathogen, exhibits resistance to polymyxins through various mechanisms.
• Inner and outer membrane integrity and lipopolysaccharide modification are key factors in polymyxin resistance.

Purpose of the Study:

• To investigate the role of Oligoribonuclease (Orn) in polymyxin resistance in Pseudomonas aeruginosa.
• To elucidate the mechanism by which Orn influences bacterial survival and polymyxin B interaction.
• To identify novel defense strategies employed by P. aeruginosa against polymyxin antibiotics.

Main Methods:

• Generating and characterizing an orn mutant of P. aeruginosa PA14.
• Assessing bacterial survival following polymyxin B treatment.
• Utilizing fluorescence-labeled polymyxin B to quantify surface-bound antibiotic.
• Investigating the role of extracellular polysaccharide Pel and extracellular DNA (eDNA) in polymyxin resistance.

Main Results:

• Mutation of orn significantly increased P. aeruginosa survival after polymyxin B exposure.
• The orn mutation led to increased binding of polymyxin B to the bacterial surface.
• Deletion of Pel synthesis genes or Pel hydrolase treatment reduced both surface-bound polymyxin B and bacterial survival.
• Pel was found to bind eDNA, forming a complex that sequesters polymyxin B.

Conclusions:

• Oligoribonuclease (Orn) plays a critical role in regulating P. aeruginosa resistance to polymyxin B.
• The Pel exopolysaccharide, in conjunction with eDNA, constitutes a novel defense mechanism against polymyxin antibiotics.
• Understanding this mechanism offers potential avenues for developing strategies to overcome polymyxin resistance.