Grau R, de Mendoza D
Departamento de Microbiología, Facultad de Ciencias, Universidad Nacional de Rosario, República Argentina.
Mol Microbiol. 1993 May;8(3):535-42. doi: 10.1111/j.1365-2958.1993.tb01598.x.
Bacillus subtilis synthesizes, almost exclusively, saturated fatty acids, when grown at 37 degrees C. When cultures were transferred from 37 degrees C to 20 degrees C, a chloramphenicol- and rifampicin-sensitive synthesis of a C-16 unsaturated fatty acid was observed. Synthesis of this compound reached a plateau after 5 h at 20 degrees C, reaching levels of 20% of the total fatty acid content. [14C]-labelled fatty acids attached as thioesters to acyl-carriers compounds, such as coenzyme A (CoA) or acyl-carrier protein (ACP) synthesized de novo by glycerol-requiring auxotrophs deprived of glycerol to arrest phospholipid synthesis, could not be desaturated at 20 degrees C. Desaturation of these fatty acids was readily observed when glycerol was restored to the cultures allowing resumption of transfer of acyl-moieties from acyl-thioesters to phospholipid. It was also observed that depletion of the pools of CoA and ACP by starvation of pantothenate auxotrophs had no effect on the observed synthesis of unsaturated fatty acid at 20 degrees C. The overall results indicate that synthesis of unsaturated fatty acids in B. subtilis is a cold-inducible process and that phospholipids are obligate intermediates in this fatty acid desaturation pathway.
枯草芽孢杆菌在37℃生长时几乎只合成饱和脂肪酸。当培养物从37℃转移到20℃时，观察到一种对氯霉素和利福平敏感的C-16不饱和脂肪酸的合成。这种化合物的合成在20℃下5小时后达到平稳期，达到总脂肪酸含量的20%。通过剥夺甘油以阻止磷脂合成的需甘油营养缺陷型菌株从头合成的硫酯连接的[14C]标记脂肪酸，如辅酶A（CoA）或酰基载体蛋白（ACP），在20℃下不能去饱和。当向培养物中恢复甘油，使酰基部分从酰基硫酯转移到磷脂的过程得以恢复时，很容易观察到这些脂肪酸的去饱和。还观察到，泛酸营养缺陷型菌株饥饿导致CoA和ACP库耗尽，对在20℃下观察到的不饱和脂肪酸合成没有影响。总体结果表明，枯草芽孢杆菌中不饱和脂肪酸的合成是一个冷诱导过程，并且磷脂是该脂肪酸去饱和途径中的必需中间体。
