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Updated: Jan 10, 2026

A Visual Assay to Monitor T6SS-mediated Bacterial Competition
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Mechanisms of Pseudomonas aeruginosa resistance to type VI secretion system attacks

Alejandro Tejada-Arranz1, Annika Plack1, Minia Antelo-Varela1,2

  • 1Biozentrum, University of Basel, Basel, Switzerland.

Nature Communications
|November 28, 2025
PubMed

Insights

Pseudomonas aeruginosa resists bacterial Type VI Secretion System (T6SS) attacks using pathways like the GacA/GacS regulon and OprF. Some resistance mechanisms increase antibiotic susceptibility, revealing complex links.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • The Type VI Secretion System (T6SS) is crucial for bacterial competition and infection by delivering toxic effectors.
  • Pseudomonas aeruginosa possesses multiple T6SSs, including the H1-T6SS, which responds to external T6SS attacks.
  • Mechanisms underlying bacterial resistance to T6SS assaults remain largely unknown.

Purpose of the Study:

  • To identify genetic pathways conferring resistance to T6SS effectors in Pseudomonas aeruginosa.
  • To investigate the role of specific regulons and outer membrane proteins in T6SS defense.

Main Methods:

  • Utilized a CRISPR interference (CRISPRi) genetic screen.
  • Tested resistance against T6SS effectors from Acinetobacter baylyi and Vibrio cholerae.

Main Results:

  • Identified members of the GacA/GacS regulon (e.g., mag operon, aas) as crucial for T6SS resistance.
  • Discovered GacA-independent factors, such as the outer membrane protein OprF, also contribute to resistance.
  • Observed that some T6SS resistance mechanisms correlate with increased susceptibility to antibiotics.

Conclusions:

  • The GacA/GacS pathway and OprF are key components of Pseudomonas aeruginosa's T6SS defense.
  • T6SS resistance mechanisms can have pleiotropic effects, impacting antibiotic susceptibility.
  • These findings highlight intricate evolutionary connections between T6SS function and antibiotic resistance.

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