Ciprofloxacin Causes Persister Formation by Inducing the TisB toxin in Escherichia coli

Tobias Dörr,Marin Vulić,Kim Lewis,Matt K Waldor

doi:10.1371/journal.pbio.1000317

Tobias Dörr, Marin Vulić + Show 2 more

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https://doi.org/10.1371/journal.pbio.1000317

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Journal: PLoS Biology	Publication Date: Feb 23, 2010
Citations: 712	License type: CC BY 4.0

Affiliation: Northeastern University

Abstract

Author SummaryBacterial populations contain a small number of dormant cells (persisters) that are tolerant to antibiotics. Persisters are not mutants, but rather phenotypic variants of regular cells. Persisters play a major role in resistance of bacterial biofilms to death, and are likely to be responsible for recalcitrance of chronic infections to antibiotics. A lead into the mechanism by which these specialized survivor cells arise comes from the fact that DNA damage induces the SOS response in bacteria, a signaling pathway that up-regulates DNA repair functions. SOS response induction also leads to expression in E. coli of a tisB “toxin” gene encoding a small membrane-acting peptide that leads to a decrease in ATP and can kill cells if artificially overexpressed. We reasoned that tisB may actually be a persister gene and its product induces reversible dormancy by shutting down cell metabolism. We show that a knockout of tisB resulted in a sharply decreased frequency of persisters tolerant to ciprofloxacin, an antibiotic that causes DNA damage, whereas mild overproduction of the peptide induced persister formation. TisB-dependent persisters also were highly tolerant to unrelated antibiotics. It appears that production of persisters tolerant to all antimicrobials is a “side-effect” of fluoroquinolone antibiotics. Our results suggest that induction of TisB by the SOS response controls production of multidrug-tolerant cells and represents, to our knowledge, the first mechanism of persister formation.

Highlights

Bacterial populations form persisters, dormant cells that are highly tolerant to antibiotics and play an important role in recalcitrance of biofilm infections [1,2]
Bacterial populations contain a small number of dormant cells that are tolerant to antibiotics
Persisters play a major role in resistance of bacterial biofilms to death, and are likely to be responsible for recalcitrance of chronic infections to antibiotics

Summary

Introduction

Bacterial populations form persisters, dormant cells that are highly tolerant to antibiotics and play an important role in recalcitrance of biofilm infections [1,2]. Gain-of-function mutants in the E. coli hipA toxin gene lead to an increase in the frequency of ampicillinand fluoroquinolone-tolerant persisters in a growing population from 1 in 10,000 cells or less (wild-type levels) to 1 in 100 cells [6,7,8,9,10], and this hipA7 mutant was shown to form persisters prior to addition of antibiotic [11]. Wild-type persisters have been isolated from an exponential culture of E. coli untreated with antibiotic, by sorting out dim cells of a strain expressing a degradable GFP that is transcriptionally fused to a ribosomal RNA promoter [12] This indicated that persisters are cells that have diminished protein synthesis and are dormant. The apparent dormancy of persisters accounts for their tolerance to bactericidal antibiotics whose action requires an active, functional target [13,14,15,16]

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