Bicarbonate Evokes Reciprocal Changes in Intracellular Cyclic di-GMP and Cyclic AMP Levels in Pseudomonas aeruginosa

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Molecular Biology

Background:

• Pseudomonas aeruginosa biofilms are a major cause of morbidity and mortality in cystic fibrosis (CF).
• Second messengers cyclic di-GMP and cyclic AMP regulate bacterial lifestyle transitions.
• Environmental factors like pH and bicarbonate influence bacterial behavior.

Purpose of the Study:

• To investigate the effects of extracellular pH and bicarbonate on intracellular cyclic di-GMP and cyclic AMP levels.
• To determine the impact of these factors on P. aeruginosa biofilm formation.

Main Methods:

• P. aeruginosa cultures were exposed to varying concentrations of NaCl or NaHCO3 at different pH levels.
• Intracellular cyclic di-GMP and cyclic AMP concentrations were measured.
• Biofilm formation was assessed using real-time cell analysis and crystal violet assays.

Main Results:

• Bicarbonate (HCO3−) exposure dose-dependently decreased cyclic di-GMP and increased cyclic AMP levels.
• Biofilm formation was significantly reduced after 48-hour exposure to bicarbonate.
• Changes in second messenger concentrations were independent of medium pH or osmolality.

Conclusions:

• Bicarbonate per se modulates cyclic di-GMP and cyclic AMP levels in P. aeruginosa.
• This modulation inhibits biofilm formation and promotes a planktonic lifestyle.
• Findings offer insights into managing P. aeruginosa infections in CF.