Thermoplasma acidophilumis an archaeon able to grow in extreme conditions of pH 1-4 and temperatures between 39 and 59°C. Since the organism lacks a cell wall, the cell membrane must be resistant and stable to protect the cytoplasm from life-threatening environmental influences. Pentacyclization and ether bonds contribute to the structural stability of tetraether lipids (TEL) as membrane constituents. In this work, molecular dynamic simulations of TEL membrane with  dimension were used including an implicit solvent “generalized born with simple switching” (GBSW) model. The influence of temperatures (39 and 59°C), pH (1.5 and 4), and the number of pentacycles (zero, three, and five denoted NPC, TPC, FPC, respectively) is simulated at 100ps. Analysis is based on the structure, interaction energy, and root mean squared deviation (RMSD) of all atoms and with these three variations, a model with four membrane states was established for each number of pentacycles: State A (pH 4; T= 39°C), state B (pH 4; T= 59°C), state C (pH 1.5; T= 39°C), and state D (pH 1.5; T= 59°C). The distance between the polar head groups denoting the thickness of the hydrophobic membrane moiety of all different structures is obtained between 21Å and 23Å. NPC exerts the longest distance and FPC the shortest distance. Based on interaction energy calculations, the lowest bond energy and RMSD of all atoms are obtained for FPC at state D (81.03kcal/mol and 8.13Å). This result is consistent with culture growth conditions at pH 1.5 and 59°C and TEL with five pentacycles (FPC) strongly contributing to the stability of the cell membrane.

tetraether lipid membrane, main polar lipid, pentacyclization, implicit solvent, molecular dynamics simulations, cell lysis, growth temperature.