Sweet Charles R, Alpuche Giancarlo M, Landis Corinne A, Sandman Benjamin C
Chemistry Department, 572M Holloway Road, United States Naval Academy, Annapolis, MD 21402, USA.
Mar Drugs. 2014 Jul 9;12(7):4126-47. doi: 10.3390/md12074126.
Lipid A is the essential component of endotoxin (Gram-negative lipopolysaccharide), a potent immunostimulatory compound. As the outer surface of the outer membrane, the details of lipid A structure are crucial not only to bacterial pathogenesis but also to membrane integrity. This work characterizes the structure of lipid A in two psychrophiles, Psychromonas marina and Psychrobacter cryohalolentis, and also two mesophiles to which they are related using MALDI-TOF MS and fatty acid methyl ester (FAME) GC-MS. P. marina lipid A is strikingly similar to that of Escherichia coli in organization and total acyl size, but incorporates an unusual doubly unsaturated tetradecadienoyl acyl residue. P. cryohalolentis also shows structural organization similar to a closely related mesophile, Acinetobacter baumannii, however it has generally shorter acyl constituents and shows many acyl variants differing by single methylene (-CH2-) units, a characteristic it shares with the one previously reported psychrotolerant lipid A structure. This work is the first detailed structural characterization of lipid A from an obligate psychrophile and the second from a psychrotolerant species. It reveals distinctive structural features of psychrophilic lipid A in comparison to that of related mesophiles which suggest constitutive adaptations to maintain outer membrane fluidity in cold environments.
脂多糖A是内毒素（革兰氏阴性脂多糖）的关键成分，是一种强效免疫刺激化合物。作为外膜的外表面，脂多糖A的结构细节不仅对细菌致病性至关重要，而且对膜完整性也至关重要。这项研究使用基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）和脂肪酸甲酯（FAME）气相色谱-质谱联用（GC-MS）对两种嗜冷菌——海生嗜冷单胞菌（Psychromonas marina）和嗜冷嗜盐杆菌（Psychrobacter cryohalolentis）以及与它们相关的两种嗜温菌的脂多糖A结构进行了表征。海生嗜冷单胞菌的脂多糖A在结构组织和总酰基大小上与大肠杆菌惊人地相似，但包含一个不寻常的双不饱和十四碳二烯酰基残基。嗜冷嗜盐杆菌的结构组织也与密切相关的嗜温菌鲍曼不动杆菌相似，但其酰基成分通常较短，并且显示出许多相差单个亚甲基（-CH2-）单元的酰基变体，这是它与先前报道的耐冷脂多糖A结构共有的特征。这项研究是首次对专性嗜冷菌的脂多糖A进行详细的结构表征，也是第二次对耐冷菌的脂多糖A进行结构表征。它揭示了嗜冷菌脂多糖A与相关嗜温菌脂多糖A相比独特的结构特征，这些特征表明嗜冷菌在寒冷环境中为维持外膜流动性而进行的组成性适应。
