Differential decomposition of arbuscular mycorrhizal fungal hyphae and glomalin

Arbuscular mycorrhizal fungi (AMF) are obligate symbionts of most higher plants. In addition to being a major component of soil microbial biomass, AMF hyphae produce glomalin, a recalcitrant glycoproteinaceous substance highly correlated with soil aggregate water stability. This study addresses the lack of knowledge concerning the decomposition of hyphae and glomalin. We used an experimental design that exploited the lack of saprobic capabilities of AMF hyphae by incubating field soil samples in the dark, and hence in the absence of plant or AMF hyphal growth. In 150 days, hyphal length decreased 60%, while glomalin, quantified by the Bradford protein assay, declined only 25%. Immuno-reactive glomalin decreased 46%. This study serves as a proof-of-concept for further examination of factors that influence decomposition of AMF hyphae using similar experimental designs.