Open AccessExpression of the phytochrome operon in Pseudomonas aeruginosa is dependent on the alternative sigma factor RpoS
Author(s) -
Barkovits Katalin,
Harms Andrea,
Benkartek Corinna,
Smart James L.,
FrankenbergDinkel Nicole
Publication year - 2008
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2007.01058.x
Subject(s) - rpos , operon , sigma factor , quorum sensing , biliverdin , phytochrome , tetrapyrrole , biology , mutant , heme oxygenase , biochemistry , genetics , microbiology and biotechnology , chemistry , gene , heme , gene expression , promoter , botany , red light , enzyme , virulence
Phytochromes are red/far‐red light photoreceptors found in plants, cyanobacteria and heterotrophic bacteria. Biochemical analyses have established that the genes bphO and bphP (PA4116 and PA4117) of Pseudomonas aeruginosa encode both phytochrome components: BphO, a heme oxygenase that produces the linear tetrapyrrole chromophore biliverdin IXα, and BphP, the apo‐phytochrome. Reverse transcription‐PCR established that both genes form a bicistronic operon. Expression of the bphOP operon was induced in the stationary phase, indicating an involvement of the P. aeruginosa quorum‐sensing system and/or the stationary‐phase alternative sigma factor RpoS. Bioinformatic analyses of the promoter region revealed a potential binding site for the quorum sensing regulators LasR and/or RhlR. While a direct involvement of the quorum‐sensing system could be ruled out, the dependence of bphOP expression on RpoS was clearly demonstrated. Chromosomal knock‐out mutants showed identical growth behavior as a wild type under various conditions but increased levels of pyocyanin were detected in the Δ bphO strain. Additionally, this strain showed decreased heat tolerance in the stationary phase, indicating a potential protective role of the BphO reaction product biliverdin. Therefore, BphO might have an additional function besides providing the chromophore for BphP and both proteins are likely to fulfill a task in the stationary phase.