Yersinia enterocolitica is capable of growing in a broad range of temperatures from 4 to 45 C. How this organism alters its membrane lipids in response to the change of growth temperature is very interesting. The fatty acids of membrane lipids of cells cultured at 5, 15, 25 and 37 C were analyzed and the physical states of these membrane lipids were characterized. The major phospholipids of this bacterium were phosphatidylethanolamine, phosphatidylglycerol, cardiolipin, lysophosphatidylglycerol and lysophosphatidylethanolamine.No significant difference in phospholipid composition in response to culture temperatures was observed. It was reported in our previous paper that the major fatty acids of membrane phospholipids of Y. enterocolitica were C15: 0, C16:0, C16: 1, cyclopropane C17: 0 and C18: 0. Some differences in the fatty acid composition were, however, observed with the change of culture temperature. When the culture temperature was raised, the saturated and cyclopropane fatty acids substantially increased and the unsaturated ones decreased. A. reverse phenomenon was observed when culture temperature was lowered. From the viewpoints of membrane physical state, adaptational changes were analyzed using a nylon microcapsule method. Phase transition in membrane lipids of cells grown at each culture temperature took place in the range of about 5 C below and about 10 C above the culture temperature.It is, therefore, considered that Y. enterocolitica maintains its membrane rigidity and fluidity in response to growth temperature by changing the membrane fatty acid composition.

The fatty acids of Yersinia enterocolitica were investigated by Abbas and Card. In their report, they stated that the major fatty acids were C16:0, C16:1, C17:0 and C18: 1 and branched or cyclopropane side-chain fatty acids could not be detected. We, however, found a moderate amount of cyclopropane side-chain fatty acid. We could determine that this fatty acid was cis-9, 10-methylene hexadecanoic acid by gas-liquid chromatography, gas chromatography-mass spectrometry, silvernitrate-treated TLC and PtO2 catalyzing hydrogenation method.Y. enterocolitica is one of the enteric bacteria, which grows in a broad range of temperature, 4-45 C. It is well known that such bacteria maintain the fluidity and stability of their membrane by changing the lipid composition following the change in growth temperature.From this point of view, we have analyzed the lipids of Y. enterocolitica.Abbas and Card, using Y. enterocolitica TN559582 strain, analyzed splendidly the fatty acid change following the change in growth temperature and found that unsaturated fatty acids increased relatively when the growth temperature decreased and saturated fatty acids increased relatively when the temperature increased (1).In their report, they stated that the major fatty acids were C16:0, C16: 1, C17:0 and C18:1, and branched or cyclopropane side-chain fatty acids could not be detected. We, however, found a moderate amount of cyclopropane side-chain fatty acids through our investigation.Y. enterocolitica Ye3827 (presented from Prof. Misao Tsubokura, Dept. of Veterinary Microbiology, Faculty of Agriculture, Tottori University) was cultured by shaking in heart-infusion broth at 25 C, the optimum-growth temperature. The cells were harvested at the late log phase and washed in cold 0.85% saline. Membrane fraction was obtained by ultracentrifugation after the cells were broken up with French press. The lipids were extracted with chloroform-methanol (2: 1, v/v) and purified by Folch's method (3). Phospholipid composition was analyzed by two-dimensional chromatography on Kieselgel 60G plate (4). The solvent system used was chloroform-methanol-water (65: 25: 4, v/v/v) in the first direction and chloroform-77

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