The AQ biosynthetic pathway and pqs genes.

Schematic representation of the AQ biosynthetic pathway and the pqs and phn genes in P. aeruginosa PAO1 and the isogenic ∆4AQ and ∆5AQ mutants. Main elements of the pqs QS system (HHQ, PQS, HQNO, PqsE, and PqsR) are in bold face. The PA number is indicated below the genes according to the Pseudomonas Genome Database [13]. Solid grey arrows represent biosynthesis; dashed grey arrows represent information flow; solid black arrow indicates activation (+); black T-line indicates negative regulation (-).