Thematic Excellence Program (Semmelweis University)(2020-4.1.1.-TKP2020) Funder: Ministry
for Innovation and Technology
(UNKP-20-5)
(NKFIH-PD:12827)
Subjects:
Clinical medicine
The formation of Pseudomonas aeruginosa biofilms in cystic fibrosis (CF) is one of
the most common causes of morbidity and mortality in CF patients. Cyclic di-GMP and
cyclic AMP are second messengers regulating the bacterial lifestyle transition in
response to environmental signals. We aimed to investigate the effects of extracellular
pH and bicarbonate on intracellular c-di-GMP and cAMP levels, and on biofilm formation.
P. aeruginosa was inoculated in a brain–heart infusion medium supplemented with 25
and 50 mM NaCl in ambient air (pH adjusted to 7.4 and 7.7 respectively), or with 25
and 50 mM NaHCO3 in 5% CO2 (pH 7.4 and 7.7). After 16 h incubation, c-di-GMP and cAMP
were extracted and their concentrations determined. Biofilm formation was investigated
using an xCelligence real-time cell analyzer and by crystal violet assay. Our results
show that HCO3− exposure decreased c-di-GMP and increased cAMP levels in a dose-dependent
manner. Biofilm formation was also reduced after 48 h exposure to HCO3−. The reciprocal
changes in second messenger concentrations were not influenced by changes in medium
pH or osmolality. These findings indicate that HCO3− per se modulates the levels of
c-di-GMP and cAMP, thereby inhibiting biofilm formation and promoting the planktonic
lifestyle of the bacteria.
