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Functions required for extracellular quinolone signaling by Pseudomonas aeruginosa
Larry A Gallagher1, Susan L McKnight, Marina S Kuznetsova
1Department of Genome Sciences, University of Washington, Seattle, Washington 98195, USA.
Abstract:
A set of 30 mutants exhibiting reduced production of the phenazine poison pyocyanin were isolated following transposon mutagenesis of Pseudomonas aeruginosa PAO1. The mutants could be subdivided into those with defects in the primary phenazine biosynthetic pathway and those with more pleiotropic defects. The largest set of pleiotropic mutations blocked the production of the extracellular Pseudomonas quinolone signal (PQS), a molecule required for the synthesis of secondary metabolites and extracellular enzymes. Most of these pqs mutations affected genes which appear to encode PQS biosynthetic functions, although a transcriptional regulator and an apparent response effector were also represented. Two of the genes required for PQS synthesis (phnA and phnB) had previously been assumed to encode phenazine biosynthetic functions. The transcription of one of the genes required for PQS synthesis (PA2587/pqsH) was regulated by the LasI/R quorum-sensing system, thereby linking quorum sensing and PQS regulation. Others of the pleiotropic phenazine-minus mutations appear to inactivate novel components of the quorum-sensing regulatory network, including one regulator (np20) previously shown to be required for virulence in neutropenic mice.
Insights
Researchers identified Pseudomonas aeruginosa mutants with reduced pyocyanin production, revealing new links between phenazine biosynthesis, Pseudomonas quinolone signal (PQS) production, and quorum sensing regulation.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Pseudomonas aeruginosa produces pyocyanin, a phenazine toxin crucial for its virulence.
- Phenazine production is tightly regulated and linked to other virulence factors.
- The Pseudomonas quinolone signal (PQS) is a key molecule in secondary metabolite synthesis.
Purpose of the Study:
- To identify and characterize Pseudomonas aeruginosa mutants with defects in pyocyanin production.
- To elucidate the genetic basis of phenazine biosynthesis and its regulation.
- To investigate the relationship between phenazine production, PQS signaling, and quorum sensing.
Main Methods:
- Transposon mutagenesis of Pseudomonas aeruginosa PAO1.
- Isolation and characterization of 30 phenazine-deficient mutants.
- Analysis of mutant phenotypes, including pleiotropic effects.
- Identification of genes involved in phenazine and PQS biosynthesis.
- Investigation of regulatory links, including quorum sensing.
Main Results:
- 30 mutants with reduced pyocyanin production were isolated.
- Mutants were categorized into those affecting primary phenazine biosynthesis and those with pleiotropic defects.
- The largest group of pleiotropic mutants showed defects in Pseudomonas quinolone signal (PQS) production.
- Several genes involved in PQS biosynthesis were identified, including two previously thought to be involved in phenazine synthesis (phnA and phnB).
- PA2587/pqsH gene transcription was regulated by the LasI/R quorum-sensing system, linking quorum sensing to PQS regulation.
- Novel quorum-sensing regulatory network components were identified, including a virulence regulator (np20).
Conclusions:
- Phenazine biosynthesis in Pseudomonas aeruginosa is interconnected with PQS production and quorum sensing.
- The study identified novel genes and regulatory mechanisms involved in phenazine and PQS synthesis.
- These findings provide new insights into the complex regulatory network governing Pseudomonas aeruginosa virulence factors.