Post‐transcriptional regulation of gene PA 5507 controls P seudomonas quinolone signal concentration in P . aeruginosa

Summary P seudomonas aeruginosa can sense and respond to a myriad of environmental signals and utilizes a system of small molecules to communicate through intercellular signaling. The small molecule 2‐heptyl‐3‐hydroxy‐4‐quinolone ( P seudomonas   Q uinolone S ignal [ PQS ]) is one of these signals and its synthesis is important for virulence. Previously, we identified an R pi R ‐type transcriptional regulator, Q ap R , that positively affects PQS production by repressing the qap R operon. An in‐frame deletion of this regulator caused P . aeruginosa to produce a greatly reduced concentration of PQS . Here, we report that Q ap R translation is linked to the downstream gene PA 5507 . We found that introduction of a premature stop codon within qap R eliminates transcriptional autorepression of the qap R operon as expected but has no effect on PQS concentration. This was investigated with a series of lac Z reporter fusions which showed that translation of Q ap R must terminate at, or close to, the native qap R stop codon in order for translation of PA 5507 to occur. Also, it was shown that truncation of the 5′ end of the qap R transcript permitted PA 5507 translation without translation of Q ap R . Our findings led us to conclude that PA 5507 transcription and translation are both tightly controlled by Q ap R and this control is important for PQS homeostasis.