Related Experiment Video

Updated: Mar 6, 2026

Overexpressing and Purifying a Toxic Nuclease from Escherichia coli
08:13

Overexpressing and Purifying a Toxic Nuclease from Escherichia coli

Published on: August 29, 2025

843

Cytotoxic Effect Associated with Overexpression of QNR Proteins in Escherichia coli

Jesús Machuca1,2, Paula Diaz de Alba1, Esther Recacha1

  • 11 Unidad Intercentros de Enfermedades Infecciosas, Microbiología y Medicina Preventiva, Hospital Universitario Virgen Macarena , Seville, Spain .

Microbial Drug Resistance (Larchmont, N.Y.)
|March 14, 2017
PubMed
Abstract

Insights

Overexpressing Qnr genes in Escherichia coli causes significant bacterial death and cell damage, unlike QepA2. This cytotoxicity varies by Qnr protein family.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Bacterial Genetics

Background:

  • Quinolone resistance in bacteria is a growing public health concern.
  • Plasmid-mediated quinolone resistance (PMQR) mechanisms contribute to reduced susceptibility to fluoroquinolone antibiotics.
  • The cytotoxic effects of PMQR gene overexpression in bacteria are not fully understood.

Purpose of the Study:

  • To investigate the cytotoxic impact of overexpressing various Qnr-like PMQR mechanisms in Escherichia coli.
  • To compare the cytotoxic effects of different Qnr families and the QepA2 efflux pump.

Main Methods:

  • Cloning and overexpression of PMQR genes (qnrA1, qnrB1, qnrC, qnrD1, qnrS1, qepA2, efsqnr) in E. coli BL21.
  • Utilizing E. coli BL21 with and without an empty vector as controls.
  • Assessing cytotoxicity via transmission electron microscopy and bacterial viability assays.

Main Results:

  • Overexpression of qnr genes led to significant bacterial viability loss (77-97%), similar to EfsQnr (97%).
  • No viability loss was observed with QepA2 overexpression.
  • Transmission electron microscopy revealed morphological changes in 30-45% of cells overexpressing EfsQnr and Qnr proteins, compared to <5% in controls and QepA2-overexpressing cells.

Conclusions:

  • Overexpression of qnr genes induces a cytotoxic cellular and structural effect in E. coli.
  • The extent of cytotoxicity is dependent on the specific Qnr protein family involved.
Keywords:
E. colicytotoxic effectqnr

More Related Videos

Non-Invasive Model of Neuropathogenic Escherichia coli Infection in the Neonatal Rat08:27

Non-Invasive Model of Neuropathogenic Escherichia coli Infection in the Neonatal Rat

Published on: October 29, 2014

11.6K
Quantification of Violacein in Chromobacterium violaceum and Its Inhibition by Bioactive Compounds07:13

Quantification of Violacein in Chromobacterium violaceum and Its Inhibition by Bioactive Compounds

Published on: August 8, 2025

1.8K

Related Concept Videos

Gene Regulation in Microbial Communities: Quorum Sensing01:28

Gene Regulation in Microbial Communities: Quorum Sensing

Quorum sensing is a mechanism of bacterial communication that enables coordinated gene expression in response to changes in population density. This facilitates collective behaviors that enhance survival, resource acquisition, and ecological adaptation. This process relies on small signaling molecules called autoinducers that accumulate as bacterial populations grow. When a critical threshold concentration of autoinducers is reached, bacterial cells collectively modify gene expression,...
799
Stringent Response in E. coli01:23

Stringent Response in E. coli

Bacterial growth is closely tied to nutrient availability, with cells proliferating exponentially under favorable conditions and entering a stationary phase when resources become scarce. This transition is mediated by a regulatory mechanism known as the stringent response, which allows bacteria to adapt to nutrient deprivation by modulating gene expression and metabolic activity.During nutrient scarcity, intracellular amino acid levels decline. It results in the accumulation of uncharged tRNAs...
422