The main objective of this project is to test experimentally the validity of a novel membrane model proposed to explain the composition and stability of the membranes of the hyperthemophilic archaea Thermococcus barophilus. This model proposes that apolar lipid molecules populate the midplane of the membrane bilayer, increasing membrane rigidity, impermeability and temperature resistance. We will reconstruct archaeal membranes in presence or absence of apolar lipids and determine the impact of apolar lipids on the membrane ultrastructure and characterize the impact of the intraplanar lipids layer on the specific physico-chemical characteristics of the membrane.