The nitrogen dioxide increases Pseudomonas fluorescens biofilm formation: identification of the bacterial response to air pollutant

Background Nitrogen dioxide is an air pollutant of increasing interest in biology. Exposure of animals to NO2results in several toxic effects, mostly lung injury.ObjectivesAware ofthe effect of NO2on pseudomonalbiofilm formation, we looked for the mechanismsof bacterialresponsethat could explain their resistance to NO2.MethodsThe confocal microscopy was used for biofilm studying, completed by motility assays. In a second time, in silicoand in vitrogenomics tools were used to narrow our research scope. Additionally, as a strategy to characterize the mechanism of P. fluorescens resistanceto NO2pollutionthese data were completed with proteomics and lipidomics studies. For this purpose, the MALDI-TOF MS Imaging was coupled to HPTLCand compiled with the traditional GC-MS.ConclusionsWhen the NO2increases P. fluorescens biofilm formation, the bacterial motility decreases. In coherence, the level of cyclic di-GMP evolves in NO2exposed cells. The lipidic study shows no drastic change in membrane charge and its composition in phospholipids and fatty acids. This suggests that NO2free radical could freely pass through membrane.In contrast, NO2promotes an extensive modification in protein production, notably the over-production of the proteins of stress response, involved in oxidative stress tolerance and iron transport/metabolism. Thus both iron up-regulation and C-di-GMP level could be signals for biofilm development.This knowledge should probably offer therapeutical solutions in antibacterial treatment.