Dual control of hydrogen cyanide biosynthesis by the global activator GacA in Pseudomonas aeruginosa PAO1


*Corresponding author. Tel.: +41 (21) 692 56 31; Fax: +41 (21) 692 56 35, E-mail: dieter.haas@lbm.unil.ch


The global response regulator GacA of Pseudomonas aeruginosa PAO1 positively controls the production of the quorum sensing signal molecule N-butanoyl-homoserine-lactone (C4-HSL) and hence the synthesis of several C4-HSL-dependent virulence factors, including hydrogen cyanide (HCN). This study presents evidence that GacA positively influences the transcription of the rhlI gene, specifying C4-HSL synthase, explaining the quorum sensing-dependent transcriptional control of the HCN biosynthetic genes (hcnABC). In addition, GacA was found to modulate hcn gene expression positively at a post-transcriptional level involving the hcnA ribosome-binding site. Thus, the activating effect of GacA on cyanogenesis results from both transcriptional and post-transcriptional mechanisms.