Lipidomics of Soil Fungal Communities.

Arbuscular mycorrhizal (AM) and saprophytic fungal communities play major roles in the cycling of nutrients in agricultural soil systems. Monitoring of their biomass and activity is essential to understand their functions in soils. Specific fatty acids can be used to detect and quantify the fungal communities – 16:1omega5c for mycorrhizal fungi communities and 18:2omega6,9c for saprophytic fungi. The abundance ratio of these fatty acids in polar lipids vs neutral lipids can indicate if the communities are in an active phase of hyphal development or in a resting, sporulating phase. Over the past 10 years, the field of mass spectrometry as applied to lipid analysis has greatly expanded. Complex lipids have become analyzable as intact molecules and this has opened the door to the discovery of more specific and sensitive lipid biomarkers. In this paper, we use a shotgun lipidomics approach through tandem mass spectrometry in order to detect new intact lipid biomarkers that contain the fatty acids specific to AM and saprophytic fungi. Agricultural soils were profiled using a succession of tandem mass spectrometry experiments. This approach enables the elucidation of a wealth of diverse new microbial biomarkers and is an essential tool in understanding the functions of these microbes in our soils.