Regulation and function of the phytochrome system in $\textit {Pseudomonas aeruginosa}$

Abstract

Phytochromes are red/far-red light photoreceptors found in plants and have recently also been discovered in bacteria. Biochemical analysis established that the genes $\it {bphO}$ and $\it {bphP}$ display the two necessary phytochrome components in the opportunistic pathogen $\textit {Pseudomonas aeruginosa: bphO}$ encoding a heme oxygenase that produces the chromophore biliverdin IX$\alpha$ and $\it {bphP}$ encoding the apo-phytochrome. Transcriptional analyses established that both genes form a bicistronic operon. Expression of the $\it {bphOP}$ operon was shown to be induced in the stationary phase dependent on the alternative sigma factor, RpoS. Interestingly, the loss of BphO but not BphP led to pronounced phenotypes in the stationary phase suggesting an additional role of BphO besides providing the chromophore to BphP. Transcriptome and proteom studies on the other hand revealed that BphP is involved in the regulation of various gene clusters and pointed to a link of BphP function with the $\textit {P. aeruginosa}$ quorum sensing system