Center of Excellence on Environmental Health and Toxicology (EHT)
| Bacterial ability to overcome host defense is one of a key factor for bacteria including Pseudomonas aeruginosa, which is an important human pathogen, to infect host successfully. In this study, bioinformatic analysis of P. aeruginosa PAO1 genome reveals the presence of PA0242 encoding putative 4-hydroxyphenylpyruvate dioxygenase enzyme. Previous study in our laboratory showed that PA0242 (hpd) mutation led to an oxidative stress sensitive phenotype. PA0243 gene encoding TetR transcriptional regulator is located downstream of PA0242 gene in a head to tail manner. RT-PCR result showed that PA0243 and tetR genes were transcribed as an operon. Expression of both hpd and tetR were induced upon exposure to oxidants including hydrogen peroxide, cumene hydroperoxide and paraquat. Expression of hpd gene in a tetR mutant was elevated indicting the role of TetR as a transcription repressor of hpd gene. The oxidant induction of hpd expression is TetR dependent. The direct interaction between hpd promoter and TetR protein was shown by gel shift assay and DNasel footprinting assay. Mechanistic insight into how bacteria fight against oxidative stress, one of important host defense, could indicate the defense system as a drug target to control infection.
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