Glomalin production by an arbuscular mycorrhizal fungus: a mechanism of habitat modification?

We report on a novel mechanism by which arbuscular mycorrhizal fungi may be able to modify a sub-optimal growth environment to their advantage by secreting the glycoprotein glomalin, which is highly correlated with soil aggregate water stability. Here we used glass beads of different sizes to simulate different hyphal growing space conditions. With small beads (<106 μm; simulating a non-aggregated soil) fungal hyphal length was reduced over 80% compared to large beads (710–1180 μm; simulating an aggregated soil). Conversely, glomalin yield (immunoreactive protein) was more than seven times higher in the small bead growing space. The results challenge our thinking about soil aggregation as a consequence of general biological activity in soil, and uncover a new aspect of the biology of these ecologically important soil fungi.