Impact of gaseous NO₂ on p. fluorescens strain in the membrane adaptation and virulence

Abstract

Nowadays air pollution is increasing due to anthropogenic activity. Among all air pollutants, nitrogen oxides (NOx) such as NO 2 are predominant. It is well known that those compounds exhibit direct toxic effects on human health. However, microorganisms are also exposed to them, but the effect of NOx on the virulence of air microbiota is still poorly understood. In this study, we evaluated the impact of NO 2 on the adaptability and virulence of an airborne strain of P. fluorescens, MFA76a, by exposition of this strain to 45 ppm of NO 2. The growth kinetics and cultivability were analysed. A decrease of cultivability coupled with an increase of the lag phase was observed suggesting a potential toxicity of NO 2. Since NOx particularly target lipids, the membrane permeability was assessed thanks to Live Dead tests and confocal microscopy. A significant alteration of membrane permeability was observed. Furthermore, more abundant bacterial aggregates were detected compared to the control. Thus, a lipidomic study was performed using MALDI-TOF MS Imaging coupled to HPTLC. Interestingly, bacteria exposed to NO 2 were lacking one putative glycerophospholipid molecule. In agreement with a previous study from Kondakova et al., these data demonstrate the adaptation potential of P. fluorescens MFAF76a to an air pollutant such as NO 2 .

Dialog between skin and its microbiota: Emergence of “Cutaneous Bacterial Endocrinology”

“…Nowadays, many QS autoinducers, such as the N‐acyl homoserine lactones (AHL) and quinolones (Gram‐negative bacteria) [ 5 ] and linear or cyclic peptides (Gram‐positive bacteria) [ 6 ] or furanosyl autoinducer 2, [ 7 ] produced by both type of microorganisms have been identified. Some species would also communicate through volatile organic compounds (nitrogen oxides) [ 8 ] and/or specific needle‐like structures (type VI secretion system). [ 9 ] Within natural microbiota, the bacterial chat is intense and modulated by degradation enzymes as AHL‐lactonases‐acylases, or peptidases, targeting specific QS factors through a mechanism designated as “Quorum Quenching.” [ 10 ] In parallel, bacteria also communicate with eukaryotic cells.…”

Gaseous NO2 induces various envelope alterations in Pseudomonas fluorescens MFAF76a

“…In a previous study, we showed slight modifications in the phospholipid composition of P. fluorescens MFAF76a membranes after exposure to NO 2 , including the disappearance of a minor unknown glycerophospholipid (UGP), but no lipid peroxidation seems to take place 33 . These previous results combined with the observed membrane alterations noted in Fig.…”

“…Therefore, the fluorescence polarization is proportional to the fluidity of the lipid bilayer in which the probe is inserted 31 , 32 . DPH behavior can also be affected by its ratio to lipids, but previous gas chromatography analysis did not show any difference in terms of quantity, composition and cis/trans ratio of fatty acid between the two conditions 33 . Our results showed that fluorescence anisotropy was significantly reduced to 0.192 after bacterial exposure to NO 2 (45 ppm) as compared to 0.217 for control condition (synthetic air), indicating an increased membrane fluidity (Fig.…”

“…This increase of the number of cells of high size could be the result of an alteration of the cell division process. This alteration is however temporary as the generation time of the bacteria published in Depayras et al were not different after exposure to NO 2 33 . The growth curve displayed a lag phase, which was at least partially explained by a significant diminution of cell viability.…”

The Hidden Face of Nitrogen Oxides Species: From Toxic Effects to Potential Cure?

“…In contrast, a direct gaseous NO 2 exposure could also be benefit in the struggle against undesirable microorganism because it seems to impact their metabolism, social behavior, and growth [84]. Moreover, a continuous high-dose NO 2 exposure seems to lead in membrane alteration through an increased permeability [98].…”