RESUMEN
Seeking effective ways to maintain cellular homeostasis is crucial to the survival of organisms when they encounter osmotic stress. Glycine betaine (GB) is a widely generated natural osmolyte, but its endogenous production and action are limited. Herein, a kind of nonionic surfactant dodecyl-ß-d-glucopyranoside (DG) and a common polymer polyethylene glycol (PEG) are proven to have the ability to enhance the osmotic stress (induced by sugar concentration changes) tolerance of cell and organism models, those are giant unilamellar vesicles (GUVs) and gram-negative Escherichia coli. DG or PEG only induces small size decrease and certain shape change of GUVs. Importantly, DG or PEG at the concentration 100 times lower than that of GB effectively increases the survival rate of bacteria under both hypoosmotic and hyperosmotic conditions. This intriguing result is attributed to the insertion of DG or adsorption of PEG in the lipid bilayer membrane, leading to enhanced membrane permeability. These exogenous substances can replace GB to facilely and highly efficiently augment adaptation of organisms to osmotic stress.
RESUMEN
Antibacterial amphiphiles normally kill bacteria by destroying the bacterial membrane. Whether and how antibacterial amphiphiles alter normal cell membrane and lead to subsequent effects on pathogen invasion into cells have been scarcely promulgated. Herein, by taking four antibacterial gemini amphiphiles with different spacer groups to modulate cell-mimic phospholipid giant unilamellar vesicles (GUVs), bacteria adhesion on the modified GUVs surface and bacteria engulfment process by the GUVs are clearly captured by confocal laser scanning microscopy. Further characterization shows that the enhanced cationic surface charge of GUVs by the amphiphiles determines the bacteria adhesion amount, while the involvement of amphiphile in GUVs results in looser molecular arrangement and concomitant higher fluidity in the bilayer membranes, facilitating the bacteria intruding into GUVs. This study sheds new light on the effect of amphiphiles on membrane bilayer and the concurrent effect on pathogen invasion into cell mimics and broadens the nonprotein-mediated endocytosis pathway for live bacteria.