PDF(Pubmed)
Abstract：
The degree of cyclization, or ring index (RI), in archaeal glycerol dibiphytanyl glycerol tetraether (GDGT) lipids was long thought to reflect homeoviscous adaptation to temperature. However, more recent experiments show that other factors (e.g., pH, growth phase, and energy flux) can also affect membrane composition. The main objective of this study was to investigate the effect of carbon and energy metabolism on membrane cyclization. To do so, we cultivated Acidianus sp. DS80, a metabolically flexible and thermoacidophilic archaeon, on different electron donor, acceptor, and carbon source combinations (S0/Fe3+/CO2, H2/Fe3+/CO2, H2/S0/CO2, or H2/S0/glucose). We show that differences in energy and carbon metabolism can result in over a full unit of change in RI in the thermoacidophile Acidianus sp. DS80. The patterns in RI correlated with the normalized electron transfer rate between the electron donor and acceptor and did not always align with thermodynamic predictions of energy yield. In light of this, we discuss other factors that may affect the kinetics of cellular energy metabolism: electron transfer chain (ETC) efficiency, location of ETC reaction components (cytoplasmic vs. extracellular), and the physical state of electron donors and acceptors (gas vs. solid). Furthermore, the assimilation of a more reduced form of carbon during heterotrophy appears to decrease the demand for reducing equivalents during lipid biosynthesis, resulting in lower RI. Together, these results point to the fundamental role of the cellular energy state in dictating GDGT cyclization, with those cells experiencing greater energy limitation synthesizing more cyclized GDGTs.IMPORTANCESome archaea make unique membrane-spanning lipids with different numbers of five- or six-membered rings in the core structure, which modulate membrane fluidity and permeability. Changes in membrane core lipid composition reflect the fundamental adaptation strategies of archaea in response to stress, but multiple environmental and physiological factors may affect the needs for membrane fluidity and permeability. In this study, we tested how Acidianus sp. DS80 changed its core lipid composition when grown with different electron donor/acceptor pairs. We show that changes in energy and carbon metabolisms significantly affected the relative abundance of rings in the core lipids of DS80. These observations highlight the need to better constrain metabolic parameters, in addition to environmental factors, which may influence changes in membrane physiology in Archaea. Such consideration would be particularly important for studying archaeal lipids from habitats that experience frequent environmental fluctuations and/or where metabolically diverse archaea thrive.
摘要：
目的：一些古细菌制造独特的跨膜脂质，在核心结构中具有不同数量的五元或六元环，调节膜的流动性和渗透性。膜核心脂质组成的变化反映了古菌对胁迫的基本适应策略，但是多种环境和生理因素可能会影响对膜流动性和渗透性的需求。在这项研究中,我们测试了Acidianussp.当使用不同的电子供体/受体对生长时，DS80改变了其核心脂质组成。我们表明，能量和碳代谢的变化显着影响DS80核心脂质中环的相对丰度。这些观察结果强调了更好地限制代谢参数的必要性，除了环境因素，这可能会影响古细菌膜生理的变化。这样的考虑对于研究来自经历频繁的环境波动和/或代谢多样的古细菌茁壮成长的栖息地的古细菌脂质特别重要。
