This infographic is targeted at Key Stage 3 students, communicating my work on using untargeted metabolomics to assess soil quality and microbial function.
What’s in the soil?
Soils in different places have different properties: they could be sandy, salty, waterlogged or full of nutrients. Lots of microbes live in the soil. Microbes are really important because they keep the soil healthy. We can see what these microbes are doing by detecting the metabolites that they produce. Metabolites are small chemicals, like sugars and fats. Microbes in soils all do the same basic things to stay alive, like eating and respiring. But some have to deal with extra stress, like being too wet, acidic or salty. When this happens, metabolites tend to build up. The types of metabolites that soil microbes produce are different depending on the properties of the soil.
Nutrient rich soils:
Farmed soils at the bottom of the hill are warm, full of nutrients and have a neutral pH. Microbes here are not stressed, so metabolites do not build up.
Peaty soils on top of the hill are cold and exposed. They are also very acidic. Lots of metabolites build up in these soils as it is hard for microbes to survive.
Soils support a wide range of ecosystem services that underpin Earth system functioning. It is therefore essential that we have robust approaches to evaluate how anthropogenic perturbation affects soil quality and the delivery of these services. Metabolomics, the large-scale study of low molecular weight organic compounds in soil, offers one potential approach to characterise soils and evaluate the metabolic status of the soil biological community. The aims of the present study were to 1) characterise the soil metabolome across a contrasting range of soil types, 2) understand the relationships between common chemical and physical soil quality indicators and its metabolome, and 3) evaluate the discriminatory power of soil metabolomics and its potential use as a soil quality indicator.
Nine different topsoils with 5 replications were collected along an altitudinal primary productivity gradient encompassing a wide range of soil types and land uses. Metabolites were extracted from soil using 3:3:2 (v/v/v) acetonitrile:isopropanol:water and individual compounds identified using a gas chromatography-mass spectrometry (GC-MS) platform.
Overall, 405 individual compounds were detected, of which 146 were positively identified, including sugars, amino acids, organic acids, nucleobases, sugar alcohols, lipids and a range of secondary metabolites. The concentration and profile of metabolites was found to vary greatly between the soil types. Further, the soils’ metabolomic fingerprints correlated to a number of environmental factors, including pH, land-use, moisture and salinity. We also tentatively attributed soil-specific metabolites to potential functional pathways, although complementary proteomic, genomic and transcriptomic approaches would be needed to provide definitive supporting evidence.
Soil metabolomics offers the potential to reveal the complex molecular networks and metabolic pathways operating in the soil microbial community and a means of evaluating soil function. Further work is now required to benchmark soil metabolomes under a wide range of management regimes so that they can be used for the quantitative assessment of soil quality.
Emma gained her Undergraduate degree in Biochemistry from the University of Bath in 2015. She then went on to complete an MSc in Conservation and Land Management at Bangor University. She currently manages a STEM outreach project at Bangor University and will be commencing her Envision PhD ‘Extreme weather events exacerbate nitrous oxide emissions from soil (Extreme-N2O)’ in October 2020.
Organisation: Bangor University