The Volatilome: A Vital Piece of the Complete Soil Metabolome
The Volatilome: A Vital Piece of the Complete Soil Metabolome
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DOI：
10.3389/fenvs.2021.649905
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发表时间：
2021-04
期刊：
影响因子：
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通讯作者：
L. Honeker;Kelsey R. Graves;M. Tfaily;J. Krechmer;L. Meredith
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文献类型：
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作者：
L. Honeker;Kelsey R. Graves;M. Tfaily;J. Krechmer;L. Meredith
土壤具有复杂的生物过程，与微生物和植物的代谢输入交织在一起。测量土壤代谢组可以揭示活跃的代谢途径，从而深入了解特定生物的存在和生态相互作用。代谢组的一个子集是挥发性的;然而，目前的土壤研究很少考虑挥发性有机化合物（VOCs），有助于样品处理和代谢组学分析技术的偏差。因此，我们假设总体而言，使用当前代谢组学分析技术测量的检测到的化合物的挥发性将低于未检测到的化合物，这反映了遗漏的VOC。为了说明这一点，我们研究了泥炭地代谢组学数据集收集使用三种常见的代谢组学分析技术：核磁共振（NMR），气相色谱-质谱（GC-MS），傅立叶变换离子回旋共振质谱（FT-ICR-MS）。我们映射的化合物的三种代谢途径（单萜类化合物的生物合成，二萜类化合物的生物合成，多环芳烃降解），选择他们的活动在泥炭地生态系统和参与挥发性有机化合物。我们通过计算相对挥发性指数（RVI）来估计化合物的挥发性，并且正如假设的那样，在我们的每个焦点途径中未检测到的化合物的平均RVI高于检测到的化合物（p < 0.001）。此外，即使在观察到较低RVI化合物的子途径中，也不存在较高RVI化合物。我们的研究结果表明，典型的土壤代谢组学分析技术可能会忽略挥发性有机化合物，并在代谢途径中留下缺失的环节。为了更完整地代表土壤代谢组的挥发性组分，我们建议环境科学家在设计和解释他们的数据时考虑这些偏差，并/或添加直接在线测量方法，以捕获VOC在土壤系统中的整体作用。
Soils harbor complex biological processes intertwined with metabolic inputs from microbes and plants. Measuring the soil metabolome can reveal active metabolic pathways, providing insight into the presence of specific organisms and ecological interactions. A subset of the metabolome is volatile; however, current soil studies rarely consider volatile organic compounds (VOCs), contributing to biases in sample processing and metabolomic analytical techniques. Therefore, we hypothesize that overall, the volatility of detected compounds measured using current metabolomic analytical techniques will be lower than undetected compounds, a reflection of missed VOCs. To illustrate this, we examined a peatland metabolomic dataset collected using three common metabolomic analytical techniques: nuclear magnetic resonance (NMR), gas chromatography-mass spectroscopy (GC-MS), and fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). We mapped the compounds to three metabolic pathways (monoterpenoid biosynthesis, diterpenoid biosynthesis, and polycyclic aromatic hydrocarbon degradation), chosen for their activity in peatland ecosystems and involvement of VOCs. We estimated the volatility of the compounds by calculating relative volatility indices (RVIs), and as hypothesized, the average RVI of undetected compounds within each of our focal pathways was higher than detected compounds (p < 0.001). Moreover, higher RVI compounds were absent even in sub-pathways where lower RVI compounds were observed. Our findings suggest that typical soil metabolomic analytical techniques may overlook VOCs and leave missing links in metabolic pathways. To more completely represent the volatile fraction of the soil metabolome, we suggest that environmental scientists take into consideration these biases when designing and interpreting their data and/or add direct online measurement methods that capture the integral role of VOCs in soil systems.