Hyphal exploration strategies and habitat modification of an arbuscular mycorrhizal fungus in microengineered soil chips

Arbuscular mycorrhizal fungi (AMF) are considered ecosystem engineers, but the interactions of their mycelium with their immediate surroundings are largely unknown. In this study, we used microfluidic chips, simulating artificial soil structures, to study foraging strategies and habitat modification of Rhizophagus irregularis symbiotically associated to carrot roots. AMF hyphae foraged over long distances in nutrient-void spaces, preferred straight over tortuous passages, anastomosed and showed strong inducement of branching when encountering obstacles. We measured bi-directional transport of cellular content inside active hyphae and documented stra-tegic allocation of biomass within the mycelium via cytoplasm retraction from inefficient paths. R. irregularis modified pore-spaces in the chips by clogging pores with irregularly shaped spores. We suggest that studying AMF hyphal behaviour in spatial settings can explain phenomena reported at bulk scale such as AMF modification of water retention in soils. The use of microfluidic soil chips in AMF research opens up novel opportunities to study their ecophysiology and interactions with both biotic and abiotic factors.

Automated summary

This study used microfluidic chips to investigate foraging strategies and habitat modification of Rhizophagus irregularis symbiotically associated with carrot roots. The researchers found that AMF hyphae can forage over long distances, prefer straight passages, and show branching induction when encountering obstacles. They also observed bi-directional transport of cellular content inside the hyphae and strategic allocation of biomass within the mycelium. Additionally, the AMF hyphae modified the pore-spaces in the chips by clogging them with irregularly shaped spores. These findings have important implications for understanding the impact of AMF on water retention in soils.