Bacillus thuringiensisis knownby its insecticidal property. The insecticidal proteins are producedat different growth stages, including the cytolytic protein (Cyt2Aa2),which is a bioinsecticide and an antimicrobial protein. However, thebinding mechanism (and the interaction) of Cyt2Aa2 on lipid bilayersis still unclear. In this work, we have used quartz crystal microbalancewith dissipation (QCM-D) and atomic force microscopy (AFM) to investigatethe interaction between Cyt2Aa2 protein and (cholesterol-)lipid bilayers.We have found that the binding mechanism is concentration dependent.While at 10 μg/mL, Cyt2Aa2 binds slowly on the lipid bilayerforming a compliance protein/lipid layer with aggregates, at higherprotein concentrations (100 μg/mL), the binding is fast, andthe protein/lipid layer is more rigid including holes (of about alipid bilayer thickness) in its structure. Our study suggests thatthe protein/lipid bilayer binding mechanism seems to be carpet-likeat low protein concentrations and pore forming-like at high proteinconcentrations. [ABSTRACT FROM AUTHOR]