Fatty acid-based lipids comprise a small but important component of soil organic matter. Lipids are indispensable components of soil microbes due to their function as components of membranes and as stores of energy and C. Hence, lipid composition is likely under strong selection pressure and there ought to be strong associations between lipid composition of microbial communities and environmental conditions. Associations between microbial lipids and environment likely involve an integrated combination of differences in lipid headgroups (classes) and fatty acyl chains. However, past studies examining associations between soil lipid composition and environmental conditions have focussed on fatty acids hydrolysed from polar lipids and less is known about headgroups (classes) of polar lipids. The aim of this study was to examine associations between environmental conditions changing with altitude and the intact polar and non-polar lipids of soil microbial communities. We used two altitudinal transects, both spanning from forest through to above the alpine treeline, but separated from one another by ~700 km. Liquid chromatography-mass spectrometry identified 174 intact lipids to the level of class and sum composition. Approximately half of the pool of fatty acid-based lipids was accounted for by two classes of non-polar lipids (diacylglycerol and triacylglycerols), while the other half was dominated by three classes of polar lipids (phosphatidylethanolamine, phosphatidylcholine and diacylglyceryl-N,N,N-trimethylhomoserine). There were large differences among sites in the relative amounts of lipid classes. For example, diacylglyceryl-N,N,N-trimethylhomoserine varied among sites from 5 to 41% of the polar lipid pool, phosphatidylcholine from 31 to 60% of the polar lipid pool, and diacylglycerols from 9 to 53% of the total non-polar pool. Relationships of lipid composition with altitude were weak or differed between transects, and pH was the variable most strongly associated with lipid composition. Variation among sites in the relative abundance of phosphatidylcholine were positively associated with pH, while relative and absolute abundance of diacylglycerol was negatively related to pH. We suggest that the accumulation of diacylglycerol at low pH represents slowed hydrolysis and/or microbial utilisation. A large fraction of variance among sites in lipid composition remained unexplained, which highlights the need for additional research on processes leading to production and consumption of fatty acid-based lipids.

基于脂肪酸的脂质占土壤有机质的很小但很重要的组成部分。脂质是土壤微生物不可或缺的组成部分，因为它们的功能是作为膜的成分以及能量和碳的存储。因此，脂质的组成可能在强大的选择压力下发生，微生物群落的脂质组成与环境条件之间应该有很强的联系。微生物脂质与环境之间的关联可能涉及脂质头基（类别）和脂肪酰基链差异的综合结合。但是，过去研究土壤脂质组成与环境条件之间关系的研究集中在从极性脂质水解的脂肪酸上，对极性脂质的头基（类别）了解较少。这项研究的目的是研究环境条件随海拔高度变化与土壤微生物群落完整的极性和非极性脂质之间的联系。我们使用了两个海拔断面，它们都从森林延伸到高山林线以上，但彼此之间相距约700公里。液相色谱-质谱法鉴定了174种完整的脂质，达到了类别和总成分的水平。基于脂肪酸的脂质池中约有一半是由两类非极性脂质（二酰甘油和三酰基甘油）构成的，而另一半则是由三类极性脂质（磷脂酰乙醇胺，磷脂酰胆碱和二酰基甘油-甘油）主导的。我们使用了两个海拔断面，它们都从森林延伸到高山林线以上，但彼此之间相距约700公里。液相色谱-质谱法鉴定了174种完整的脂质，达到了类别和总成分的水平。基于脂肪酸的脂质池中约有一半是由两类非极性脂质（二酰甘油和三酰基甘油）构成的，而另一半则是由三类极性脂质（磷脂酰乙醇胺，磷脂酰胆碱和二酰基甘油-甘油）主导的。我们使用了两个海拔断面，它们都从森林延伸到高山林线以上，但彼此之间相距约700公里。液相色谱-质谱法鉴定了174种完整的脂质，达到了类别和总成分的水平。基于脂肪酸的脂质池中约有一半是由两类非极性脂质（二酰甘油和三酰基甘油）构成的，而另一半则是由三类极性脂质（磷脂酰乙醇胺，磷脂酰胆碱和二酰基甘油-甘油）主导的。N，N，N-三甲基高丝氨酸）。脂质类别的相对量之间的位点之间存在很大差异。例如，二酰基甘油基-N，N，N-三甲基高丝氨酸的位置在极性脂质池的5％到41％之间，磷脂酰胆碱在极性脂质池的31％到60％之间以及二酰基甘油在总非极性池的9％到53％之间变化。样带之间脂质组成与海拔的关系较弱或有所不同，pH是与脂质组成最密切相关的变量。磷脂酰胆碱相对丰度中位点之间的变化与pH呈正相关，而二酰基甘油的相对和绝对丰度与pH呈负相关。我们建议在低pH值下积累二酰基甘油代表减缓的水解和/或微生物利用。脂质组成部位之间的很大一部分差异仍无法解释，