FIGURE 6.

Regulatory network of iron, PrrF, anthranilate, and quorum sensing in P. aeruginosa. A, under iron-depleted conditions, PrrF represses antABC and catABC, sparing anthranilate for PQS synthesis. The repression of antA by PrrF may occur by direct interaction with the antA mRNA and indirectly via degradation of the antR mRNA. Iron also activates expression of antR, leading to activation of antA, by an unknown, PrrF-independent, mechanism. Iron may also activate expression of genes encoding enzymes in the kynurenine pathway, providing anthranilate for PQS production under high iron conditions. TCA, tricarboxylic acid. B, AntR, an AraC-type regulator, activates expression of antR, antABC, and possibly catBCA. Anthranilate increases the ability of AntR to bind to the antA promoter and activates expression of antR and antABC. Quorum-sensing regulators (QscR, LasR, RhlR, and PqsR) also coordinate the expression of antR and antABC.