PDF(Pubmed)
Abstract：
The sole unifying feature of the incredibly diverse Archaea is their isoprenoid-based ether-linked lipid membranes. Unique lipid membrane composition, including an abundance of membrane-spanning tetraether lipids, impart resistance to extreme conditions. Many questions remain, however, regarding the synthesis and modification of tetraether lipids and how dynamic changes to archaeal lipid membrane composition support hyperthermophily. Tetraether membranes, termed glycerol dibiphytanyl glycerol tetraethers (GDGTs), are generated by tetraether synthase (Tes) by joining the tails of two bilayer lipids known as archaeol. GDGTs are often further specialized through the addition of cyclopentane rings by GDGT ring synthase (Grs). A positive correlation between relative GDGT abundance and entry into stationary phase growth has been observed, but the physiological impact of inhibiting GDGT synthesis has not previously been reported. Here, we demonstrate that the model hyperthermophile Thermococcus kodakarensis remains viable when Tes (TK2145) or Grs (TK0167) are deleted, permitting phenotypic and lipid analyses at different temperatures. The absence of cyclopentane rings in GDGTs does not impact growth in T. kodakarensis, but an overabundance of rings due to ectopic Grs expression is highly fitness negative at supra-optimal temperatures. In contrast, deletion of Tes resulted in the loss of all GDGTs, cyclization of archaeol, and loss of viability upon transition to the stationary phase in this model archaea. These results demonstrate the critical roles of highly specialized, dynamic, isoprenoid-based lipid membranes for archaeal survival at high temperatures.
摘要：
令人难以置信的多样化古菌的唯一统一特征是其基于类异戊二烯的醚连接的脂质膜。独特的脂质膜成分，包括丰富的跨膜四醚脂质，赋予抵抗极端条件。还有很多问题,然而,关于四醚脂质的合成和修饰以及古细菌脂质膜组成的动态变化如何支持超嗜热。四醚膜,被称为甘油二植酸甘油酯四醚（GDGTs），由四醚合酶（Tes）通过连接两个称为古细菌的双层脂质的尾巴而产生。GDGT通常通过GDGT环合酶(Grs)添加环戊烷环来进一步特化。已观察到相对GDGT丰度与进入静止期生长之间存在正相关，但是抑制GDGT合成的生理影响以前没有报道过。这里,我们证明，当删除Tes（TK2145）或Grs（TK0167）时，超嗜热柯达热菌模型仍然可行，允许在不同温度下进行表型和脂质分析。GDGTs中不存在环戊烷环不会影响柯达红藻的生长，但是在超最佳温度下，由于异位的Grs表达而导致的环过多是高度健康的阴性。相比之下,Tes的缺失导致所有GDGTs的丢失，古菌醇的环化，在该模型古细菌中过渡到固定期时，生存能力丧失。这些结果证明了高度专业化的关键作用，动态,基于类异戊二烯的脂质膜用于高温下古细菌的存活。
