(p)ppGpp controls bacterial persistence by stochastic induction of toxin-antitoxin activity

Area of Science:

• Microbiology
• Bacterial Physiology
• Antibiotic Resistance

Background:

• Persistence is a key factor in antibiotic resistance, enabling bacterial survival under drug pressure.
• The underlying mechanisms of persistence in wild-type bacteria, particularly the role of slow growth, remain incompletely understood.

Purpose of the Study:

• To investigate whether slow growth in a subset of cells contributes to the persistence phenotype in wild-type Escherichia coli.
• To elucidate the regulatory pathways governing stochastic entry into the slow-growing, multidrug-tolerant state.

Main Methods:

• Stochastic analysis of wild-type Escherichia coli populations during exponential growth.
• Investigation of the roles of (p)ppGpp, Lon protease, inorganic polyphosphate, and toxin-antitoxin systems in regulating persistence.
• Measurement of (p)ppGpp levels and their correlation with slow growth and multidrug tolerance.

Main Results:

• Rare cells within exponentially growing wild-type E. coli populations stochastically enter a slow-growth state.
• These slow-growing cells exhibit multidrug tolerance and retain the ability to resuscitate.
• The persistence phenotype is hierarchically dependent on (p)ppGpp, Lon protease, inorganic polyphosphate, and toxin-antitoxin systems.
• Stochastic variations in (p)ppGpp levels drive the transition to slow growth and persistence.

Conclusions:

• Slow growth is a critical determinant of the persistence phenotype in wild-type E. coli.
• A regulatory cascade involving (p)ppGpp, inorganic polyphosphate, and Lon protease activates toxin-antitoxin loci to induce slow growth and persistence.
• Understanding these mechanisms offers potential targets for combating antibiotic resistance.