Involved in the terminal step of the biosynthesis of quinolone which in addition to serve as a potent signal for quorum sensing, chelates iron and promotes the formation of membrane vesicles (MVs). Catalyzes the hydroxylation of 2-heptyl-4-quinolone (C7-HHQ) to yield 2-heptyl-3-hydroxy-4-quinolone (PQS). 2-heptyl-4(1H)-quinolone + H(+) + NADH + O2 = 2-heptyl-3-hydroxy-4(1H)-quinolone + H2O + NAD(+) Belongs to the 3-hydroxybenzoate 6-hydroxylase family.