Untargeted soil metabolomics methods for analysis of extractable organic matter
Untargeted soil metabolomics methods for analysis of extractable organic matter
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DOI：
10.1016/j.soilbio.2014.10.007
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发表时间：
2015-01-01
影响因子：
9.7
通讯作者：
Northen, Trent R.
中科院分区：
文献类型：
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作者：
Swenson, Tami L.;Jenkins, Stefan;Northen, Trent R.
微生物对土壤有机质（SOM）的循环是全球碳循环的一个重要组成部分，但人们对其了解甚少。有一种新的观点认为，SOM的大部分，尤其是溶解部分（DOM），是由植物和微生物来源的小分子组成的，这些小分子是由裂解的细胞和释放的代谢物产生的。不幸的是，人们对土壤的小分子组成以及这些分子是如何循环的（通过微生物或植物或通过吸附到矿物表面）知之甚少。水可萃取有机物（WEOM）部分是特别感兴趣的，因为这可能是SOM中最容易获得的生物成分。在这里，我们描述了一个简单的土壤代谢组学工作流程的发展和一种新的穗恢复方法，使用C-13细菌裂解物来评估WEOM部分中残留的代谢物类型。土壤样品采用多种质谱兼容的萃取缓冲液（水，10 mM K2SO4或NH4HCO3, 10-100%甲醇或异丙醇/甲醇/水[3:3:2 v/v/v]）进行提取，并事先进行氯仿蒸气熏蒸。采用气相色谱/质谱法（GC/MS）对衍生提取物进行分析，通过比较碎片模式和保留时间，鉴定出55种代谢物。正如预期的那样，与未消毒的样品相比，熏蒸被认为可以溶解微生物细胞，显著增加了代谢物的范围和丰度。为了评估WEOM部分中残留的细菌细胞的微生物代谢物类型，从生长在C-13醋酸盐上的土壤细菌stutzerii假单胞菌RCH2中提取了一种提取物。这种方法产生了高度标记的代谢物，易于与内源土壤代谢物区分。将新鲜细菌提取物的成分与土壤孵育15分钟后回收的成分进行比较，发现只有27%的代谢物在WEOM中显示出50%的回收率。许多，特别是阳离子（多胺）和阴离子显示
The cycling of soil organic matter (SOM) by microorganisms is a critical component of the global carbon cycle but remains poorly understood. There is an emerging view that much of SOM, and especially the dissolved fraction (DOM), is composed of small molecules of plant and microbial origin resulting from lysed cells and released metabolites. Unfortunately, little is known about the small molecule composition of soils and how these molecules are cycled (by microbes or plants or by adsorption to mineral surfaces). The water-extractable organic matter (WEOM) fraction is of particular interest given that this is presumably the most biologically-accessible component of SOM. Here we describe the development of a simple soil metabolomics workflow and a novel spike recovery approach using C-13 bacterial lysates to assess the types of metabolites remaining in the WEOM fraction. Soil samples were extracted with multiple mass spectrometry-compatible extraction buffers (water, 10 mM K2SO4 or NH4HCO3, 10-100% methanol or isopropanol/methanol/water [3:3:2 v/v/v]) with and without prior chloroform vapor fumigation. Profiling of derivatized extracts was performed using gas chromatography/mass spectrometry (GC/MS) with 55 metabolites identified by comparing fragmentation patterns and retention times with authentic standards. As expected, fumigation, which is thought to lyse microbial cells, significantly increased the range and abundance of metabolites relative to unfumigated samples. To assess the types of microbial metabolites from lysed bacterial cells that remain in the WEOM fraction, an extract was prepared from the soil bacterium Pseudomonas stutzerii RCH2 grown on C-13 acetate. This approach produced highly labeled metabolites that were easily discriminated from the endogenous soil metabolites. Comparing the composition of the fresh bacterial extract with what was recovered following a 15 min incubation with soil revealed that only 27% of the metabolites showed >50% recovery in the WEOM. Many, especially cations (polyamines) and anions, showed