The role of the cytoplasmic heme‐binding protein (PhuS) of Pseudomonas aeruginosa in quorum sensing and intracellular iron homeostasis

Abstract

Heme acquisition is a key process employed by pathogenic bacteria to obtain iron from the host. Pseudomonas aeruginosa genome has two distinct heme uptake loci, phu (Pseudomonas heme uptake) and has (heme assimilation system). In this study the role of PhuS, a cytoplasmic heme binding protein encoded by phu locus, was examined by transcriptional profiling of a phuS transposon mutant. Disruption of phuS caused premature induction of quorum sensing regulon, evidenced as early production of redox pigment, pyocyanin during exit from logarithmic into stationary phase. Surprisingly several iron-regulated genes and the genes involved in transcriptional regulation, post-translational modification and two-component signal transduction pathways were differentially expressed. Additionally, several genes involved in anaerobic mode of growth were down-regulated. Although exact mechanism, by which disruption of PhuS leads to such effects, is as yet unknown, based on the microarray analysis several potential cellular roles of PhuS emerge. These include a potential role of PhuS in cellular homeostasis of iron, magnesium and phosphate, and potential protein-protein interactions of PhuS with quorum regulators such as RpoS, MvaT, RsmA or QscR. Taken together the results presented will elucidate the complex relationship between quorum sensing, iron utilization and the intracellular heme status.