a -lauroyl ethylester (LAE), a cationic preservative derived from lauric acid and arginine, on the cell envelopes of Salmonella typhimurium and Staphylococcus aureus at sub-lethal concentration such as their respective minimal inhibitory concentrations, 32 and 8 lg ml )1 , respectively. Methods and Results:Bacterial populations were studied by using transmission electron and fluorescence microscopy (TEM and FM), flow cytometry (FC) and ion-flux across the cellular membrane. Cell integrity was altered mainly in the outer membrane of S. typhimurium, but there was no significant change in the cytoplasm. However, in Staph. aureus, clear zones, abnormal septation and mesosome-like structures were observed in the cytoplasm. Bacterial populations were double-stained with propidium iodide (PI) and SYTO-13 for FC analysis. In S. typhimurium the proportion of damaged cells after 24 h was 97% and in Staph. aureus 56AE3%. LAE induced transmembrane ion flux, the increase of potassium leakage after 30 min of contact was 7AE7 and 3AE34 lg ml )1 for Staph. aureus and S. typhimurium, respectively. Membrane disruption was detected by measuring the proton flow across the membrane. Conclusions: Disturbance in membrane potential and structural changes was caused by LAE, although cells were not disrupted. Significance and Impact of the Study: This is the first time the cellular effects of LAE on bacterial cells were studied.

No abstract

New monodisperse nonionic surfactant molecules, based on lysine with two fatty acid chains in the hydrophobic part and one or two polyoxyethylene methoxycapped chains (EOn−Me) in the hydrophilic headgroup, are synthesized as mimics of natural lecithins. Their surface‐activity properties indicate that these compounds have surfactant behavior whose global hydrophobic contribution is comparable to that of one fatty chain.

No abstract