Membrane properties of Thermoplasma acidophila.

Plasma membranes were isolated from Thermoplasma acidophila, a mycoplasma-like organism which grows optimally at pH 2 and 59 degrees. Cells in concentrated suspensions were lysed by titrating to pH 9.3. The membranes were purified by washing at pH 10 and centrifuging in a discontinuous sucrose gradient. Membrane purity was assessed by electron microscopy, determination of deoxyribonucleic acid content, polyacrylamide gel electrophoretic behavior. Gel patterns and amino acid composition of cells and membranes were found to differ significantly. The lipid contained small amounts of fatty acid esters and larger amounts of branched long-chain alkyl ethers.