Supported lipid bilayers using extracted microbial lipids: domain redistribution in the presence of fengycin.

Fengycin is an antimicrobial cyclic lipopeptide known to interact with microbial cell membranes. To gain insight into the role of lipids in fengycin sensitivity, lipids extracted from Alternaria solani, Fusarium sambucinum, and Pythium sulcatum were analyzed and used in the preparation of supported lipid bilayers (SLBs). Total Internal Reflection Fluorescence Microscopy (TIRFM) was used to evaluate lipid phase separation within the SLBs and changes in domain distribution with the application of fengycin. A. solani lipid extract contained the highest quantity of ergosterol while P. sulcatum contained no ergosterol. Sterol content of SLBs was strongly correlated with increases in phase separation, suggesting ergosterol may play a role in promoting ordering of the lipid phases in the bilayer. A. solani experienced the least change in domain characteristics following fengycin exposure, suggesting ergosterol may be buffering effects of the antimicrobial compound. Factors such as lipid headgroup charge and unsaturation levels may impact fengycin's effects on domain phase separation, but these effects were generally overshadowed by the role of ergosterol. In the absence of ergosterol, in the P. sulcatum bilayers, fengycin caused an increase in lipid phase ordering.