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As a model for the epicuticular wax layer of plant cuticular membranes, we have studied the phase behavior of 1-tetradecanol and 1-octadecanol and their binary mixtures between 5 and 70°C, using differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). Both pure compounds show two exothermic phase transitions corresponding to a transformation from a liquid phase to a hexagonally packed solid phase (SHEX), which at lower temperatures transforms to an orthorhombically-packed solid phase (SORT). On heating the SORT solid a single endothermic transition with a transition enthalpy corresponding to the sum of the exothermic transition enthalpies is obtained. These transitions were also followed using FTIR spectroscopy in the CH2-stretching (symmetric and asymmetric) and CH2-rocking vibration modes. The FTIR spectra of the pure compounds in the liquid, SHEX, and SORT phases were used to simulate experimental spectra in the phase transition regions. The simulations allowed us to estimate the molar fractions of each phase in the transition regions of the pure compounds. A phase diagram for the binary mixture of 1-tetradecanol and 1-octadecanol was obtained using differential scanning calorimetry and FTIR. FTIR studies on binary mixtures prepared from one perdeuterated component and the other nondeuterated permitted studying the thermotropic behavior of each component in the mixture independently. The mixture shows an eutectic behavior with an eutectic point between a molar fraction of octadecanol (X18) of 0.12 and 0.18 and a temperature of ∼32°C. Below 32°C, a binary mixture of solid phases, one an SORT phase and the other an SHEX phase, coexist up to ∼25°C, below which both solid phases are SORT phases. We discuss the possible relevance of this complex phase behavior in a simple binary mixture of two long-chain alkanols in the context of the far more complex phase behavior expected for the plant epicuticular wax layer.

The polar lipids and fatty acid composition ofThermus aquaticus YT-1 and YS 041,T. filiformis Wai33 A1 and eighteen isolates from New Zealand, several of which are attributed toT. filiformis, were compared to complement the taxonomy of these organisms. The polar lipid patterns were essentially similar in all strains and consisted of one major phospholipid and one major glycolipid. The fatty acid analysis produced three basic groups corresponding toT. filiformis Wai33 A1,T. aquaticus and the third to the other New Zealand strains. The presence of hydroxy fatty acids is reported inThermus spp. for the first time.

In this study we examined the fatty acid composition of 63 strains of the genus Thermusand 25 strains of the genus Meiothermus. The major fatty acids of all of the organisms were iso- and anteiso-branched. Straight chain fatty acids were, with some exceptions, present in small to moderate amounts; monounsaturated fatty acids were only detected in M. rubergrown at low temperatures. All of the strains assigned to the species T. aquaticusand the type strain of T. filiformiscontained moderate proportions of 3-hydroxy fatty acids, but none of the other Thermusstrains contained these fatty acids. On the other hand, all of the strains of M. ruber, M. silvanusand M. chliaropbiluscontained moderate amounts of 2-hydroxy fatty acids, although some strains also contained trace levels of 3-hydroxy fatty acids.