Impact of pauR transcription factor deletion in the polyamine degradation pathway on antimicrobial stress responses in Pseudomonas aeruginosa

Background:The pauR transcription factor in Pseudomonas aeruginosa (P.aeruginosa) acts as a global regulator of enzymes for polyamine utilization, and polyamine transporters encoded by spuDEFGH operon.Although spuDEFGH is linked to the type III secretion system, its role under oxidative and antibiotic stress is unclear.As some PauR-regulated genes potentially contribute to multidrug resistance, we deleted pauR instead of targeting individual genes.This study explores the impact of pauR deletion on stress responses.Objectives: This study aimed to construct pauR-deleted and pauR-expressing strains in P. aeruginosa and to investigate the role of pauR in response to antimicrobial agents,including antibiotics and oxidants.Methods: P. aeruginosa pauR strain was generated using Gibson assembly and the Cre/loxP gene-deletion system.Antibiotic and oxidant susceptibility profiles of both wild-type and mutant strains were assessed using disc diffusion and plate sensitivity assays, respectively. Results:The pauR-deleted mutant was constructed and verified through PCR-based and local genomicDNA sequence analyses.The disc diffusion test revealed no significant difference in antibiotic susceptibility levels between the tested strains.However, exposure to the superoxide generator resulted in a significantly decreased susceptibility in the pauR mutant compared to the wild type, with a 99% of confidence interval.Furthermore, an ectopic pauR expression in the pauR mutant increased its susceptibility. Conclusion:While pauR does not appear to play a key role in antibiotic resistance, it may contribute to resistance against the oxidant in P. aeruginosa.In further experiments, genes within the pauR regulon that contribute to the oxidative stress response mechanism will be identified.