Utilizing soil metabolomics to investigate the untapped metabolic potential of soil microbial communities and their role in driving soil ecosystem processes: A review

The importance of soil sustainability in achieving sustainable development goals and global environmental agreements has been widely recognized. Understanding the biological processes of soil is crucial to decipher the soil-climate feedback mechanism. Soil metabolomics is a scientific study of low molecular weight metabolites in soil, both known and unknown, and is a potential application to assess the metabolic-scenario within the soil biological community. Although soil metabolomics has been applied in assessing different aspects of soil processes, it is still in its infancy, contributing to only a small percentage of published papers on metabolomics approaches. This highlights the need for further research and focus in this area. This review discusses the emerging perception of soil metabolite dynamics and its significance in soil ecosystem function. It covers the different groups of metabolites present in soil, extraction procedures, methodological biases, and advanced instrumentation for analysis. Targeted and untargeted metabolomics techniques are presented, with nuclear magnetic resonance (NMR) and mass spectrometry (MS) found to be the most widely used methods. The review also explores soil metabolomics application in various soil ecosystem services. Water-soluble, bio-available metabolites, and volatile metabolites are found to be the most crucial info chemicals underlying soil-plantmicrobe interactions. Soil metabolomics has also been successful in characterizing soil organic matter and humus in terms of low molecular weight metabolites, indicating the direct contribution of microbes in stable organic matter formation. Additionally, it has helped in deciphering signature metabolites in response to ecotoxicity imparted by heavy metals, nanoparticles, and other soil pollutants. The strengths and weaknesses of metabolomics approaches are also discussed. Finally, key research prospects are highlighted to further improve our understanding of soil metabolomics' application in providing soil ecosystem services.