A critical review of the use of lipid signature molecules for the quantification of arbuscular mycorrhiza fungi

Tools for accurate measurements of microbial biomass/abundance are imperative in soil ecology. This perspective was prompted by a lack of consistency in how the neutral lipid fatty acid (NLFA) and phospholipid fatty acid (PLFA) 16:1ω5 are used to estimate arbuscular mycorrhizal (AM) fungal abundance, which we argue can lead to erroneous conclusions within studies and complicate among-study comparisons. We show that more than half of all studies published to date use PLFA 16:1ω5 to quantify AM fungal biomass without proper controls. This is problematic because AM fungi cannot be separated from the bacterial contribution to this fatty acid signature. We provide a set of recommendations for future research and specifically urge researchers to extract and analyze NLFA 16:1ω5 for more accurate and sensitive assessments of AM fungal biomass as this can be done without doubling effort.