Studies on Biological and Physical States of Membrane Lipids in the Adaptational Changes of Staphylococcus Aurous

细菌根据环境和细胞结构的变化而适应性地改变其细胞膜。我们报道了葡萄球菌自体质膜合成以心磷脂为主的结果，葡萄球菌L-除了合成心磷脂外，还形成新的合成胆固醇。我们从生物物理和生物化学的角度对这些现象进行了进一步的研究。为了解释为什么在缺乏细胞壁的金黄色葡萄球菌细胞中心磷脂显著增加，用差示扫描量热法研究了心磷脂和磷脂酰甘油混悬液的相变特性。二肉豆蔻基磷脂酰甘油、四肉豆蔻基心磷脂、二棕榈酰磷脂酰甘油和四烷基磷脂酰心磷脂的相变温度分别为2 5.0、47.0、40.5和6 2.2ﾟC。两种类似磷脂混合物的相变温度高于…的相变温度。高r磷脂酰甘油，但低于单用心磷脂。随着心磷脂含量的增加而增加。二价阳离子特别是Ca~(2+)和Gt~(2+)的存在使心磷脂的相变温度升高。结果表明，心磷脂的头基本身可以提高相变温度，并以脂质体中羧基荧光素的释放量为指标，考察了从正常金黄色葡萄球菌、L型金黄色葡萄球菌和口腔支原体中提取的脂类制备的脂质体的抗渗透稳定性。当脂质体在过量水流入时破裂时，捕获的羧基荧光素就会释放出来。用L型或支原体脂类制备的脂质体比由正常金黄色葡萄球菌制备的脂质体具有更强的抗渗透压能力。结果表明，心磷脂提高了金黄色葡萄球菌的膜稳定性和支原体中的胆固醇。用胶体滴定法测定了磷脂酰丝氨酸脂质体和6种细菌的表面电荷。用福尔马林完全封闭氨基，并直接滴定磷酸和羧基的负电荷。氨基可以从有无福尔马林的滴定差异中估计出来。用这种胶体滴定方法可以在每个pH值下用化学计量法计算表面电荷，用福尔马林处理可以定量地检测氨基的影响。较少

The bacteria alter their membranes adaptively according to changes of environment and cell structure. We have reported the results that staphylococcal autoplasts synthesized predominantly cardiolipin in their membranes and staphylococcal L-forms synthesized cholesterol newly in addition to an increase of cardiolipin. We have done further study toward clarification of these appearances from the viewpoints of biophysics as well as biochemistry.In order to elucidate why cardiolipin markedly increases in S. aureus cells which lack cell walls, the phase transition characteristics of cardiolipin and phosphatidylglycerol suspensions were investigated by differential scanning calorimetry. The phase transition temperatures for dimyristoylphosphatidylglycerol, tetramyristoylcardiolipin, dipalmitoylphosphatidylglycerol and tetrapalmitoylcardiolipin were 25.0, 47.0, 40.5 and 62.2^ﾟC, respectively. The phase transition temperature for a mixture of two analogous phospholipids was higher than that fo … More r phosphatidylglycerol alone, but lower than that for cardiolipin alone. It increased along with cardiolipin content. The phase transition temperature for cardiolipin was increased in the presence of divalent cations, particularly Ca^<2+>. The results indicate that the head group of cardiolipin by itself can increase the phase transition temperature.Moreover, we checked anti-osmotic stability of liposomes prepared with lipids extracted from normal S. aureus, its L-form and Mycoplasma orale, using the release of carboxyfluorescein trapped in liposomes as an indicator. The trapped carboxyfluorescein was released when the liposomes burst upon the inflow of excess water. Liposomes prepared with the lipids of L-form or Mycoplasma were more resistant to osmotic pressure than those prepared from normal S. aureus. It was found that cardiolipin enhanced the membrane-stability in S. aureus and cholesterol in Mycoplasma.The surface charge of phosphatidylserine liposome and six kinds of bacteria were determined by colloid titration. The amino group was blocked completely by formalin treatment and the negative charge of phosphate and carboxyl group was titrated directly. The amino group can be estimated from the titration difference in the presence and absence of formalin. By this colloid titration method the surface charge can be evaluated stoichrometrically at every pH value, and by formalin treatment the effect of the amino group can be detected quantitatively. Less