Distal and proximal promoters co-regulate pqsR expression in Pseudomonas aeruginosa

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Pathogenesis

Background:

• Pseudomonas aeruginosa is an opportunistic pathogen causing severe infections in immunocompromised individuals.
• Bacterial virulence is regulated by intercellular communication, with the PqsR transcription factor being crucial for Pseudomonas quinolone signal reception and pathogenicity.
• Previous research indicated LasR positively controls pqsR expression, but the mechanism remained unclear.

Purpose of the Study:

• To elucidate the regulatory mechanisms controlling pqsR gene expression in Pseudomonas aeruginosa.
• To identify and characterize the promoter sites involved in pqsR transcription.
• To understand how different regulators influence pqsR expression in response to cell-cell communication and environmental cues.

Main Methods:

• Identification and analysis of two distinct promoter regions upstream of the pqsR gene.
• Investigating the role of the quorum-sensing regulator LasR in pqsR transcription activation at the distal promoter.
• Assessing the antagonistic effect of CysB on LasR-mediated activation and the inhibitory roles of negative regulatory elements and H-NS family proteins (MvaT, MvaU) at the proximal promoter.

Main Results:

• Two separate promoter sites were discovered that contribute to pqsR expression.
• LasR positively regulates pqsR transcription via the distal promoter, an effect antagonized by CysB.
• The proximal promoter site also contributes to pqsR transcription, but its activity is repressed by a negative regulatory sequence and potentially by MvaT and MvaU.

Conclusions:

• A model is proposed where integrated positive and negative regulatory inputs at both promoter sites modulate PqsR levels.
• This complex regulatory network allows Pseudomonas aeruginosa to fine-tune PqsR expression based on environmental signals and cell-cell communication.
• Understanding these regulatory mechanisms provides insights into controlling P. aeruginosa pathogenicity.