It's probably the nastiest, slimiest computer in the world. Powered by oat flakes instead of electricity, scientists in the U.K. have developed a rudimentary computer using a slime mold they have affectionately named Plasmobot.
"Most people's idea of a computer is a piece of hardware with software designed to carry out specific tasks," said Andy Adamatzky, professor of unconventional computing at the University of the West of England.
"This mold, or plasmodium, is a naturally occurring substance with its own embedded intelligence."
Cool, shady and moist areas like decaying logs is where the Plasmobot, or Physarum polycephalum, is usually found. In the laboratory, slime mold is usually fed oat or corn flakes.
The Plasmobot performed four different functions, the most basic of which was pushing or pulling outside objects. The slime mold also performed more complex operations, such as completing mathematical constructs such as a spanning tree diagram and the Voronoi diagram, which is a collection of geometric objects that are a partition of space into cells.
Plasmobot did this with its own natural abilities; it was not genetically engineered to perform these tasks in any way. To complete the spanning tree, for instance, Adamatzky put oat flakes in specific spots around the slime mold.
The slime mold has to optimize its foraging pattern — finding the shortest route to any food source and then propagating the nutrients efficiently. The resulting protoplasmic tubes that transported the food around the slime mold represented a solution to the problem.
To complete the Voronoi diagram, the mold uses the fact that as two molds grow they encounter each other and stop growing. The boundary between the two molds becomes the solution.
Physarum polycephalum isn't the first organism co-opted for computation. E. coli, a bacteria, and other microorganisms have previously been used to solve the classic mathematical puzzle known as the Burnt Pancake problem or the Traveling Salesman problem.
There are several differences between computing with slime mold and bacteria, besides being in different kingdoms. The first is the E. coli had to be genetically engineered to solve the problems. The second is that E. coli is microscopic. A single Plasmobot can be the size of a petri dish.
Plasmobot computes very differentially from bacteria computers as well. To solve the Burnt Pancake problem the genetically engineered bacteria flipped various sections of their DNA inside their body. Plasmobot solved problems by physically moving its body.
At the moment Adamatzky, and other scientists, including Jonathan Mills at Indiana University, don't see any commercial or practical applications. There remain several stumbling blocks, including reliably replicating the experiments.
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"As all other living objects Physarum does not always behave as we want it to," said Adamatzky. "We must develop a set of experiment protocols to keep Physarum totally under our control."
Even if reliable controls can be created, a computer made of enough individual slime molds to perform meaningful calculations would be quite large, about a meter square, according to Mills.
"The barriers that need to be overcome to make this technology practical are significant," said Mills. "But the possibility of taking a biological organism and using it for a practical purpose is always exciting."
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