深海環境への微生物の適応機構に関する研究

The world's oceans cover 70% of the eath's surface,with about 3,800m of average depth.Altough　the deep-sea environment with its high pressure and low temperatures is too extreme for most terrestrial and marine surface microorganisms,many barotolerant and barophilic bacteria have been found inhabiting the deep-sea.It is exyremely important for barophilic or barotolerand deep-sea bacteria to maintain the physiological functions of cytoplasmic membrane,which serves many vital functions.The fluidity of this cytoplasimic membrane composed of phospholipids and poteins is essential for the physiological functions of cells.As higher hydorstatic pressure raise the melting point of lipids and cause phase transition of lipid under pressurs of up to 100MPa,barotolerant and barophilic bacrteria under high hydostatic pressure appear to regulate the composition of their membrane phospholipids. Therfore the characrization of cytoplasmic membrane under high pressure is indispensable to clarify the mecanisms of bacteria adaptation to the deep-sea enviroment.The effects of pressure and temperature acid compositon of barotolerant deep-sea bacteria were investigated.Deep-sea bacteria maintained their membrane fluidity by increasing the content of unique fatty acid in phospholipids under high hydrostatic pressure.Gene expression seems to be necessary for the synthesis of unique fatty under high hydrostatic pressure.