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Quorum-sensing regulator RhlR but not its autoinducer RhlI enables Pseudomonas to evade opsonization

Samantha Haller1, Adrien Franchet1, Abdul Hakkim2,3

  • 1CNRS, M3I UPR 9022, Université de Strasbourg, Strasbourg, France.

EMBO Reports
|March 11, 2018
PubMed

Insights

Pseudomonas aeruginosa virulence relies on RhlR, but RhlR has functions independent of its signal RhlI. RhlR protects bacteria from fly immune responses, with Tep4 opsonization playing a complex role in host defense.

Area of Science:

  • * Microbiology
  • * Immunology
  • * Genetics

Background:

  • * *Pseudomonas aeruginosa* can infect *Drosophila melanogaster* by crossing the intestinal barrier.
  • * Hemocytes provide cellular immunity against bacterial proliferation in the hemocoel.
  • * Quorum-sensing regulators like RhlR are crucial for bacterial evasion of host immune responses.

Purpose of the Study:

  • * To investigate the role of *Pseudomonas aeruginosa* quorum-sensing regulator RhlR and its signal RhlI in *Drosophila* infection models.
  • * To elucidate RhlR-independent functions and its interaction with the *Drosophila* immune system, specifically Tep4.
  • * To determine the dual role of Tep4 opsonization in different infection routes.

Main Methods:

  • * Intestinal and septic infection models using *Drosophila melanogaster* and nematodes.
  • * Genetic manipulation of *Pseudomonas aeruginosa* (rhlI and rhlR mutants).
  • * Assessment of bacterial virulence, hemocyte phagocytosis, and Tep4-mediated opsonization.

Main Results:

  • * *rhlI* mutants exhibited higher virulence than *rhlR* mutants in intestinal infection models, indicating RhlR's RhlI-independent functions.
  • * RhlR protects *P. aeruginosa* from Tep4-mediated opsonization, with *rhlR* mutants showing increased opsonization.
  • * In septic infections, Tep4-mutant flies were more resistant to wild-type *P. aeruginosa*, but not *rhlR* mutants, highlighting context-dependent opsonin function.

Conclusions:

  • * RhlR possesses significant RhlI-independent virulence functions in *P. aeruginosa* infections.
  • * RhlR actively protects bacteria from Tep4-mediated opsonization, impacting bacteremia.
  • * The immune protein Tep4's role is context-dependent, acting as protective or detrimental based on the infection route.
Keywords:
competition opsonization‐detection by pattern recognition receptorsinfection routeintestinal infectionphagocytosisquorum sensing

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