Slime mold: The next wet thing in computing?


A slime mold commonly called ‘dog vomit.’ (Courtesy M. Kaid)

Slime mold gets little respect. That’s particularly true of the variety called “dog vomit” for its resemblance to the real thing. The word itself – slime – has a special place in American humor and in the movies, as in “The Best Blob and Slime Monster Movies.” 

Maybe that will change now, in light of a research breakthrough published this week showing that Physarum polycephalum, slime mold, can be used as a biological computer.

The news came in the current issue of Materials Today, in which two researchers; Andrew Adamatzky and Theresa Schubert described how they managed to get slime mold to function as a logical circuit, the basic building block of the computer.

A little background: Slime molds have been known for decades for their amazing feats.

Physarum polycephalum, the “many-headed slime” is a category of brainless, single-cell, soil dwelling amoeba that network together to find food, forming tubes that branch out to transport nutrients from point A to point B and many points in between.

In the wild, explains the journal Scientific American:

P. polycephalum rummages through leaf litter and oozes along logs searching for the bacteria, fungal spores and other microbes that it envelops and digests à la the amorphous alien in the 1958 horror film The Blob. P. polycephalum often acts like a colony of cooperative individuals foraging together. … In the lab, confined to a petri dish, it usually spreads itself thin across the agar, branching like coral.”

Researchers, for example, have created complicated mazes in petri dishes, put slime mold food at the entrance and the exit and watched the slime mold plot out the most efficient route through the maze. (See videos below.)

Others have placed the food on each of the major cities of the United States, and watched the slime mold map the best routes connecting them, effectively designing a highway system.

In one famous experiment that received a Ig Nobel Awards, a scientist produced a slime mold map of the entire Tokyo transit system.

The same two researchers who did the logic circuit experiment have actually used the protoplasmic tubes of the slime mold to transport nano-beads and colored dyes.

Because of these feats, slime mold scientists have long maintained that slime molds could have use as bio-computers. That may or may not come to pass.

But Adamatzky, a professor in Unconventional Computing at the University of the West of England in Bristol, and Schubert, a “post-media” artist at Bauhaus-University Weimar, Germany, took a big step forward with their logical circuits experiment.

What they did, they report, was stimulate the slime mold mechanically, activating “gates” that open and shut, just like the logic gates of computer chips.

The “slime mold tube logical gates” blocked and redirected the flow of fragments in the tube, they report.

They also demonstrated that the “slime mold network” could carry out simple functions of Boolean logic, the algebraic system used in binary computing.

Right now, they say, the “gates are slow: their speed is on the order of seconds, much slower than silicon gates.”

On the other hand, they are “self-growing and self-repairing” and can be incorporated into “wetware,” that could detect molecules or living cells. Some day, they said, the “Physaraum microfluidic gates could form the basis of disposable biocompatible mechanically controlled devices.”

On one hand, it’s hard to know where all this will lead. On the other, who would have thought a hundred years ago that there would be a Silicon Valley?

Slimy Valley anyone?

The "gates" in magnified slime mold are marked in red. (Courtesy Theresa Schubert and David Adamatsky)
The “gates” in magnified slime mold are marked in red. (Courtesy Theresa Schubert and Andy Adamatzky)

 

 

 

 

Fred Barbash, the editor of Morning Mix, is a former National Editor and London Bureau Chief for the Washington Post.
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