Analysis of the hex regulon in Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen whose defense mechanisms include biofilm production through carbohydrate metabolism. The activity of the enzymes in the hex regulon are required for catabolism of glucose and these activities are coordinately regulated. Previous work has shown that these enzymes are induced when grown on carbohydrates and catabolite repressed when grown on TCA cycle intermediates. The HexR protein is a negative transcriptional repressor and the Crc protein participates in regulation of these genes and has been shown to be necessary for biofilm formation. The main objective of this study was to analyze control of these genes in different growth mediums and determine if Crc is a transcriptional protein or a post-transcriptional controller of the regulon. The transcriptional start sites for zwf and glk were mapped by primer extension assays. Comparisons of glk between wild type and a hexR mutant revealed the possibility of transcription without HexR control. Analysis of zwf mRNA showed that Crc affects mRNA stability and is acting at a post-transcriptional level. Â