In Situ Atomic Force Microscopy Studies of the Effect of Indolicidin on E.coli Cells

Abstract

E.coli cells were succesfully attached to both gelatin coated surfaces andpolylactic acid honeycomb patterned mica surfaces as determined by in situatomic force microscopy. The gelatin coated surfaces provided a softer supportonto which the E.coli cells were capable of slightly submerging leading to abetter adhesion compared to the harder surfaces consisting of polylactic acidpolymer surfaces. After continuous scanning in liquid media, the E.coli cellsremained rod shaped and smooth. Indolicidin, a 13-AA linear antimicrobialpeptide, was injected in order to visualize the peptide-membrane interac-tions in real time. Instantly after the injection of the peptides, the bacterialmembranes were observed to be distorted and seemed to melt proceeding as afunction of time. In conclusion, these experiments proved that the E.coli cellswere not ruptured as could be expected due to pore formation and disruptionof the osmotic pressure. This indicates a possible intracellular target killingmechanism of indolicidin interacting with E.coli cells.