The intriguing role of the biosurfactant Rhamnolipid upon plasma membrane models

Resumen

Introduction: Different strains of Pseudomonas aeruginosa are able to produce a class of biosurfactants called rhamnolipids (RLs), with significant tensioactive and emulsifying properties that, among different applications, are able to enhance oil biodegradation, particularly relevant in soil/sand bioremediation processes. RLs are glycolipid surfactants with a hydrophilic head, composed of one (mono-RL)) two (di-RL molecules) of rhamnose, connected to a hydrophobic tail, formed by one or two molecules of β-hydroxydecanoic acid. The advantages of RLs reported on the literature, in respect to synthetic ones, are low toxicity, high biodegradability and ecological safety. We here explore the impact of RLs on biomimetic membranes represented by giant unilamellar vesicles (GUVs) composed of a ternary mixture of DOPC, sphingomyelin (SM) and cholesterol (CHOL) at molar ratio 1:1:1, which displays liquid-ordered (Lo)-liquid disordered (Ld) phase coexistence. Lipid domains can dynamically assemble and diassemble in the membranes during cell signaling. Therefore, changes promoted in lipid domain organization can interfere in cell homeostasis.

Results: The insertion of mono-RL in the membrane outer leaflet is a dominant process with no pore formation and a negligible effect in modifying membrane permeability, but promotes lipid mixing. On the other hand, the addition of di-RL to the biomimetic lipid bilayer induces an outward Lo budding which, depending on the di-RL concentration, can end up in a membrane fission. Increase in Ld membrane permeability is concomitantly observ
Conclusions: Noteworthy, both biosurfactants may cause damage on plasma membranes: mono-RL promotes lipid mixing thus affecting cell signaling and di-RL induces Lo outward budding and permeability increase (pore formation) that may also conduct to cell homeostasis loss and eventually cell death.