In the past, neutron experiments proved to be successful in quantifying the extent to which macromolecular dynamics in bacterial cells is affected by adaptation to extreme temperatures and salinity (Tehei et al., 2004; Tehei et al., 2007). The results supported the hypothesis that the evolutionary selection of appropriate resilience in order to maintain macromolecular structure and flexibility within the narrow limits required by biological activity contributes to environmental adaptation. We investigated recently the effect of high hydrostatic pressure on lipid model membranes. Due to the pressure induced order, the main phase transition between the gel and the liquid state in such membranes is shifted to higher temperatures under high pressure (Peters et al., 2011). To maintain the fluidity in the membrane, more unsaturated lipids are found in organisms from deep sea environments.The objective of our project is to compare the dynamics of plasma membranes of procaryotes adapted to different environmental conditions (temperature and pressure) and to study by this way the mechanisms of environmental adaptation of biological systems.