The arbuscular mycorrhizal fungal protein glomalin: Limitations, progress, and a new hypothesis for its function

SummaryMost research on glomalin-related soil proteins (GRSP) has focused on the role of arbuscular mycorrhizal fungi in soil aggregation and environmental engineering. Recently, with the description of the glomalin gene sequence and other results, work on this protein has shifted to include fungal physiology. Based on recent findings, we develop a new model for the role of glomalin; we postulate a primary role in fungal physiology and secondarily arising effects in the soil environment that lead to observed correlations of GRSP with soil aggregate stability. Concurrent with advances in molecular biology, several recent studies have highlighted problems with quantifying GRSP from soil. We summarize and discuss limitations of the methods currently used for GRSP extraction and quantification in soils. We finish with a set of recommendations for research directions that involve testing the model proposed here.