Mycorrhizal fungi are the soil supply chain. Filaments thinner than hair close important nutrients to plants and tree roots.
In return, fungi receive carbon to grow their networks. In this way, 13 billion tons of atmospheric carbon dioxide, one-third of the world's fossil fuel emissions, enters the soil every year.
These fungi cannot live on their own. They need carbon from the plants. Second, 80% of the world's plants rely on fungal networks to survive and thrive. The two are dependent trading partners.
These fungi make very wise choices even without the brain or central nervous system. Scientists describe them as “living algorithms.”
The trading algorithm rewards reward efficiency: builds the most profitable path possible for the lowest construction costs.
The fungal network appears to assess supply and demand. Which plants need that nutrient most? What carbon do you provide? Where is the best payoff? This analysis shapes how networks expand, as scientists have learned when mapping growth in real time.
“Fungi are very smart,” said Toby Kiers, an evolutionary biologist and director for protecting the underground network, a research organization. “They are constantly adapting trade routes. They are assessing the environment very accurately. That's a lot of decisions.”
How do bacteria do that? To investigate, Dr. Kiers and her colleagues raised fungi in hundreds of Petri dishes, or “fungal arenas.”
Using imaging robots, the team then nonstop tracking the network growth for several days, measuring how organisms reshape their trade routes depending on different conditions. Their research was published in the journal Nature on February 26th.
From special nodes, or growing hints, the fungi unfold filaments that explore and evaluate new areas. Over the course of several days, scientists labeled and monitored half a million new nodes and mapped the expansion.
Growth has revealed the decision-making of active fungi. In past work, teams have learned that fungi refrain from trading with nearby roots in favor of more distant roots when returns on carbon are high.
Fungal networks are sometimes referred to as soil circulation systems.
However, in the fungal network, flows are open. Carbon, nitrogen, phosphorus, water, and even fungal nuclei move in either direction, even in opposite directions at once.
“It's physically disgusting,” said Tom Shimiz, a biophysicist at Amorph, a physicist in Amsterdam's physics laboratory, whose lab built the robot. Fungi are “basically microorganisms that play economic games. If you're just a fluid flow tube, what do you do with it?”
They do it by following some basic local rules, which after all. As the growing tips progress, new branches form behind them at a stable rate. However, when one hint comes into another, they blend into a loop.
This removes dead ends, avoids wasted expansion, and keeps resources moving quickly on the main highway. The edges of the fungal network expand like a ripple to lay efficient trading nexus.
Scientists want to understand so far how fungi move so much carbon without clogging the pipes. And they want to simulate how these ancient creatures react to wildfires, droughts and other disruptions caused by climate change. “We're trying to understand how they play the games they play,” Dr. Shimizu said.
Credits: Corentin Bisot -Amolf/Vu Amsterdam; Loreto Oyarte Gálvez -Vu Amsterdam/Amolf;Rachel Cargill-Vu Amsterdam/Amorph. Vasilis Kokkoris -Vu Amsterdam/Amolf/Spun; Joe Togneri/Spun; Loek Vugs; Sasha Supachal.
Produced by Antonio de Luca and Elijah Walker.
