Impact of the biofilm mode of growth on the inner membrane phospholipid composition and lipid domains in Pseudomonas aeruginosa

Abstract

Many studies using genetic and proteomic approaches have revealed phenotypic differences between planktonic and sessile bacteria but the mechanisms of biofilm formation and the switch between the two growth modes are not well understood yet. In this study, we focused on inner membrane lipidome modifications when Pseudomonas aeruginosa cells were grown as biofilm. Lipid analyses were performed by Electrospray Ionization Mass Spectrometry. Results showed a drastic decrease of the uneven-numbered chain phospholipids and a slight increase of long chain PEs in sessile organisms as compared with planktonic counterparts, suggesting a better lipid stability in the bilayer and a decrease in membrane fluidity. The impact of sessile growth on lipid domains was then investigated by Brewster Angle Microscopy (BAM) and Atomic Force Microscopy (AFM). Observations showed that inner membrane lipids of P. aeruginosa formed domains when the pressure was close to physiological conditions and that these domains were larger for lipids extracted from biofilm bacteria. This is coherent with the mass spectrometry analyses.

The Biofilm Lifestyle Involves an Increase in Bacterial Membrane Saturated Fatty Acids

“…Membrane composition of Gram-negative bacteria is more complex, containing CFA and cis- and trans -UFA and membrane fluidity also depends on ratios of cis- to trans -UFA and of UFA to CFA. In the literature, results about P. aeruginosa are contradictory as some authors demonstrated a decrease of membrane fluidity in biofilm cells due to increased long chain FA and decreased BCFA (Benamara et al, 2011), whereas others showed a less rigid membrane by decrease in linear SFA content and decrease in fatty acid length chains (Chao et al, 2010). …”

Effects on Membrane Lateral Pressure Suggest Permeation Mechanisms for Bacterial Quorum Signaling Molecules

“…The headgroup layer was identified as the additional binding region due to cation-π interactions with the choline groups. In the case of E. coli phosphatidylcholine is not the part of the system, but clearly is for P. aerugenosa 65 . It remains to be elucidated whether the headgroup of phosphatidyletholamine, the main E. coli phospholipid, can arrange for indole binding sites.…”

Acquisition and Role of Molybdate in Pseudomonas aeruginosa

“…Transition from the planktonic state to biofilm lifestyle has previously been shown to result in an alteration of the bacterial cell membrane lipid content (46). Consequently, we investigated the fatty acid (FA) composition of the wild-type and ⌬modA strains grown with and without KNO 3 (Fig.…”