How do am fungi navigate soil?

Despite their crucial role in ecosystems, we still have a poor understanding of how arbuscular mycorrhizal (AM) fungi physically navigate through soil. These fungi form vast underground networks of hyphae that explore their surroundings, seeking out nutrients and interacting with other soil organisms. While we know they can influence soil structure and water retention, the fine-scale mechanics of their movement and decision-making remain largely mysterious.

To investigate this, researchers challenged Rhizophagus irregularis, a common AM fungal species, to navigate a microfluidic soil chip—a miniature artificial soil environment designed to mimic the complex structure of real soils. The study revealed several key fungal behaviors:

• Hyphae strategically retracted cytoplasm from inefficient paths, reallocating resources to more promising routes.
• Hyphae branched extensively upon encountering obstacles, suggesting an adaptive search strategy.
• Fungal spores clogged small pores, physically altering their environment in ways that could impact soil properties.
• Hyphae fused (anastomosed) when encountering other hyphae, optimizing connectivity within the fungal network.

These findings provide new insight into how AM fungi navigate soil-like environments, modify their surroundings, and make strategic decisions about resource allocation. By understanding these fine-scale behaviors, we can better grasp how fungal networks contribute to larger soil processes, such as nutrient distribution and water retention. Studies like this pave the way for uncovering how AM fungi move nutrients from soils to plants, ultimately shaping plant health and ecosystem dynamics.

‍