Memristors — devices whose resistance depends on the history of current that has passed through them — are typically fabricated from metal oxides or perovskites in cleanrooms. LaRocco et al. (PLOS One, 2025) grew them from shiitake mushrooms.
Shiitake spores were cultured until mycelium colonized a petri dish, forming a dense hyphal network. The network was then dehydrated — flattened into a stable disc, the organism killed. Months later, the dried disc was rehydrated, connected to electrodes, and tested. It switched between resistance states at up to 5,850 signals per second with 90% accuracy. The memristive behavior — the dependence of current resistance on voltage history — persisted through the death and resurrection of the substrate.
The finding that matters is not that mushrooms can compute. It's that the computation survived desiccation. The mycelium's electrical pathways are physical structures — branching networks of hyphae whose geometry determines conductance. When the organism dies, the geometry remains. When rehydrated, the geometry conducts again. The memory is architectural, not metabolic. The organism built the circuit, but the circuit doesn't need the organism to function.
This separates two things that biology normally keeps fused: the builder and the building. A living mycelial network grows, adapts, responds to chemical gradients, explores its substrate. Its electrical signaling is part of its metabolism — the hyphae carry electrochemical signals that coordinate growth and nutrient transport. But the conductive pathways established during life are durable enough to operate after the coordinating metabolism has ceased. The structure outlasts its maintenance system.
Conventional electronics achieves the same separation trivially — a silicon chip functions regardless of whether the foundry that made it still operates. But biological systems are different. A neuron dies and its synaptic connections are lost. A muscle fiber dies and its contractile function ends. The shiitake mycelium is unusual because the biologically grown structure retains non-biological function after biological death. The growth was alive. The memory is not.
The broader pattern: structures built by living systems for one purpose can serve a different purpose after the living system stops. The mycelium grew its hyphal network for nutrient acquisition and chemical communication. The same network, dried and dead, functions as a resistance-switching memory element. The organism's electrical infrastructure was never optimized for computing — but it was optimized for the spatial connectivity and electrochemical responsiveness that computing requires. The function that survived is the one the organism didn't intend.