Functions Required for Extracellular Quinolone Signaling by <i>Pseudomonas aeruginosa</i>

TLDR

Pseudomonas aeruginosa genes phnA and phnB, previously thought to encode phenazine biosynthetic functions, are actually required for PQS synthesis. Transposon mutagenesis of PAO1 yielded 30 mutants with reduced pyocyanin production, enabling the isolation of phenazine‑deficient strains. These mutants split into primary phenazine‑biosynthetic defects and pleiotropic defects that largely block PQS production, implicating PQS biosynthetic genes, a LasI/R‑regulated regulator (pqsH), and novel quorum‑sensing components such as np20 that are essential for virulence.

Abstract

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.