Protective action of ppGpp in microcin J25-sensitive strains

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Physiology

Background:

• Escherichia coli exhibits increased resistance to the peptide antibiotic microcin J25 during stationary phase growth.
• Nutrient starvation (e.g., amino acids, glucose) in E. coli leads to elevated intracellular levels of guanosine 3',5'-bispyrophosphate (ppGpp).
• ppGpp levels naturally rise as bacterial cells transition into the stationary phase.

Purpose of the Study:

• To investigate the direct impact of manipulating guanosine 3',5'-bispyrophosphate (ppGpp) levels on microcin J25 sensitivity in Escherichia coli.
• To elucidate the molecular mechanisms underlying stationary phase-induced antibiotic resistance.

Main Methods:

• Artificially manipulated ppGpp levels in Escherichia coli cultures.
• Assessed bacterial sensitivity to microcin J25 under varying ppGpp concentrations.
• Investigated the role of the YojI efflux pump in microcin resistance.

Main Results:

• A direct positive correlation was observed between ppGpp accumulation and microcin J25 resistance.
• ppGpp accumulation is essential for inducing the expression of the YojI efflux pump.
• The YojI efflux pump actively expels microcin J25 from bacterial cells.

Conclusions:

• Guanosine 3',5'-bispyrophosphate (ppGpp) plays a crucial role in mediating antibiotic resistance in stationary phase Escherichia coli.
• The ppGpp-induced YojI efflux pump is a key factor in maintaining low intracellular microcin J25 levels and preventing toxicity.
• This mechanism highlights a novel bacterial defense strategy against peptide antibiotics.