Abstract：
Staphylococcus aureus is an opportunistic pathogen that is considered a global health threat. This microorganism can adapt to hostile conditions by regulating membrane lipid composition in response to external stress factors such as changes in pH and ionic strength. S. aureus synthesizes and incorporates in its membrane staphyloxanthin, a carotenoid providing protection against oxidative damage and antimicrobial agents. Staphyloxanthin is known to modulate the physical properties of the bacterial membranes due to the rigid diaponeurosporenoic group it contains. In this work, preparative thin layer chromatography and liquid chromatography mass spectrometry were used to purify staphyloxanthin from S. aureus and characterize its structure, identifying C15, C17 and C19 as the main fatty acids in this carotenoid. Changes in the biophysical properties of models of S. aureus membranes containing phosphatidylglycerol, cardiolipin, and staphyloxanthin were evaluated. Infrared spectroscopy shows that staphyloxanthin reduces the liquid-crystalline to gel phase transition temperature in the evaluated model systems. Interestingly, these shifts are not accompanied by strong changes in trans/gauche isomerization, indicating that chain conformation in the liquid-crystalline phase is not altered by staphyloxanthin. In contrast, headgroup spacing, measured by Laurdan GP fluorescence spectroscopy, and lipid core dynamics, measured by DPH fluorescence anisotropy, show significant shifts in the presence of staphyloxanthin. The combined results show that staphyloxanthin reduces lipid core dynamics and headgroup spacing without altering acyl chain conformations, therefore decoupling these normally correlated effects. We propose that the rigid diaponeurosporenoic group in staphyloxanthin and its positioning in the membrane is likely responsible for the results observed.
摘要：
金黄色葡萄球菌是一种机会病原体，被认为是全球健康威胁。这种微生物可以通过调节膜脂质组成以响应外部应激因素如pH和离子强度的变化来适应不利条件。金黄色葡萄球菌合成并在其膜中掺入了葡萄黄质，提供抗氧化损伤和抗微生物剂的类胡萝卜素。已知，由于其包含的刚性腹膜神经孢子基团，葡萄黄质可调节细菌膜的物理性质。在这项工作中,制备薄层色谱和液相色谱质谱联用技术对金黄色葡萄球菌中的葡萄黄质进行了纯化,并对其结构进行了表征,确定C15，C17和C19是该类胡萝卜素中的主要脂肪酸。含有磷脂酰甘油的金黄色葡萄球菌膜模型的生物物理特性的变化，心磷脂,和葡萄黄质进行了评估。红外光谱显示，在评估的模型系统中，葡萄黄质降低了液晶到凝胶的相变温度。有趣的是,这些变化并不伴随反式/gauche异构化的强烈变化，表明液晶相中的链构象不会被葡萄黄质改变。相比之下,头部组间距,通过LaurdanGP荧光光谱法测量，和脂质核心动力学，通过DPH荧光各向异性测量，在存在的情况下显示出显着的变化。综合结果表明，在不改变酰基链构象的情况下，黄黄质可降低脂质核心动力学和头基间距，因此去耦这些通常相关的影响。我们认为，葡萄黄质中的硬体神经孢子蛋白及其在膜中的定位可能是观察到的结果的原因。
