The effect of rhamnolipids on fungal membrane models as described by their interactions with phospholipids and sterols: An in silico study

Abstract

Introduction: Rhamnolipids (RLs) are secondary metabolites naturally produced by bacteria of the genera Pseudomonas and Burkholderia with biosurfactant properties. A specific interest raised from their potential as biocontrol agents for crop culture protection in regard to direct antifungal and elicitor activities. As for other amphiphilic compounds, a direct interaction with membrane lipids has been suggested as the key feature for the perception and subsequent activity of RLs.Methods: Molecular Dynamics (MD) simulations are used in this work to provide an atomistic description of their interactions with different membranous lipids and focusing on their antifungal properties.Results and discussion: Our results suggest the insertion of RLs into the modelled bilayers just below the plane drawn by lipid phosphate groups, a placement that is effective in promoting significant membrane fluidification of the hydrophobic core. This localization is promoted by the formation of ionic bonds between the carboxylate group of RLs and the amino group of the phosphatidylethanolamine (PE) or phosphatidylserine (PS) headgroups. Moreover, RL acyl chains adhere to the ergosterol structure, forming a significantly higher number of van der Waals contact with respect to what is observed for phospholipid acyl chains. All these interactions might be essential for the membranotropic-driven biological actions of RLs.

Chemo-Enzymatic Synthesis and Biological Assessment of p-Coumarate Fatty Esters: New Antifungal Agents for Potential Plant Protection

“…The spectra were calibrated on the solvent residual peak (CDCl 3 , δ = 7.26 ppm; acetone-d 6 , δ = 2.05 ppm; CD 3 OD, δ = 3.31 ppm) and described as follows: chemical shift in part per million (ppm), multiplicity, coupling constant, integration, and attribution. 13 C-NMR analyses were recorded at 75 MHz on a Fourier 300, Bruker (Wissenbourg, France). The spectra were calibrated on the solvent residual peak (CDCl 3 , δ = 77.16 ppm; acetone-d 6 , δ = 29.84 ppm; CD 3 OD, δ = 49.00 ppm) and described as follows: chemical shift in part per million (ppm) and attribution.…”

“…The spectra were calibrated on the solvent residual peak (CDCl 3 , δ = 77.16 ppm; acetone-d 6 , δ = 29.84 ppm; CD 3 OD, δ = 49.00 ppm) and described as follows: chemical shift in part per million (ppm) and attribution. 2D spectra, 1 H-1 H-Cosy, 1 H-13 C-HSQC, and 1 H- 13 C HMBC were used for attributing peaks. HRMS were recorded on a HPLC system Agilent 1290 coupled with PDA UV and 6545 Q-Tof.…”

“…Even if the ability to interact with the lipidic membrane is required to achieve elicitation, the molecules that exhibit such ability already described in the literature are mainly amphiphilic, such as rhamnolipids [12,13].…”

“…These compounds have similar dual effects of protecting plants through antifungal activity and stimulating local and/or systemic plant immunity. Although numerous elicitors are perceived by plasma membrane receptors, recent studies on these amphiphilic compounds suggest that they are sensed in an uncommon way involving lipids in the bilayer of the plant plasma membrane [12,13]. It seems that the amphiphilic properties of these compounds could explain their singular elicitor activity [14,15].…”

“…( • C): 72.2. 1 H NMR (300 MHz, CDCl 3 ) δ (ppm) = 7.63 (d, J = 16.1 Hz, 1H, H5), 7.41 (d, J = 8.5 Hz, 2H, H2),6.86 (d, J = 8.2 Hz, 2H, H3), 6.30 (d, J = 15.9 Hz, 1H, H6), 4.20 (t, 2H, H8), 1.70 (p, 2H, H9), 1.37-1.23 (m, 10H, H1014), 0.88 (t, 3H, H15) 13. C NMR (75 MHz, CDCl 3 ) δ (ppm) = 168.2 (C7), 158.1 (C4), 144.8 (C5), 130.0 (C2), 127.0 (C1), 115.9 (C3), 115.3 (C6), 64.9 (C8),31.8, 29.3, 29.2, 28.7, 26.0, 22.7 (C9-14), 14.11 (C15).…”