Pseudomonas aeruginosa (P.a.) is an opportunistic pathogen that chronically infects cystic fibrosis (CF) patients. Due to the extraordinary antimicrobial resistance of this organism, there are increasingly limited therapeutic options for P.a. infections. Consequently, a better understanding of its pathogenic mechanisms are critical to the development of improved therapeutics. We discovered that the transcriptional regulatory system, AlgZR, controls the expression of an array of P.a. virulence properties [1-5]. AlgZR was initially discovered as a key regulator of increased alginate production associated with pathognomic P.a. mucoid phenotype in isolates from CF patients [6, 7]. Elucidation of the signals that activate AlgZR will provide a better understanding of a large number of P.a. pathogenic mechanisms, including type IV mediated twitching motility, biofilm formation, alginate production, Rhl mediated quorum sensing and rhamnolipids. These data lead to our hypothesis: The AlgR sensor kinase, AlgZ/FimS responds to oxygen tensions, phosphorylates AlgR and activates or derepresses several genes involved in pyochelin, pyoverdine production and heme acquisition. Specific Aim 1. Since AlgR seems to be controlling several iron acquisition genes, we will perform RNA sequencing (RNA-seq) and chromatin immunoprecipitation with next generation sequencing (ChIP-seq) to determine the AlgR regulon using mucoid strains encoding two different forms of AlgR, one that is “locked on” AlgRD54E and one that is “locked off” AlgRD54N.
Specific Aim 2. We will use biochemical and genetic mechanisms to determine how AlgZ is sensing oxygen. Since AlgZ is co-transcribed with heme biosynthetic genes hemCD while fimU transcription, alginate and siderophore production are responsive to oxygen levels, we hypothesize that AlgZ binds heme and senses oxygen through heme.

SCHURR1610

2017-04-01

2018-09-01