Slime Mold in Residence

P. polycephalum spends most of jts life cycle as a giant, motile cell, known as a super-organism, that contains many genetically distinct nuclei yet acts as a unit, exhibiting cooperative behavior to optimize conditions for the whole. In addition to its collaborative tendencies, the slime mold is known for its engineering ability; when placed on a map of the U.S. with food sources at major cities, P. polycephalum branches out in a pattern like that of the US highway system.

P. polycephalum will be at Hampshire through 2019. ANDREW HART

Humans don’t need slime molds to design highways, Keats recalls thinking, but could they help us with other problems?

Human society is also like a super-organism, he says, in that individuals’ decisions affect the whole, but we’re not so good at cooperating. “We can . . . look to the slime mold as a way of being able to see how we might behave for our collective good,” Keats says. “Maybe if we were to enlist slime molds to solve problems that are more vexing for society [than civil engineering] . . . they might be able to come up with insights that would be beneficial to us.” Toward this end, the students used the slime molds to examine border policy, addiction, materialism, food deserts, and public transportation.

For instance, the addiction experiment examined, by analogy, whether gateway drugs, such as marijuana, lead to further drug use. For P. polycephalum, valerian root is addictive and harmful—equivalent, the researchers posit, to hard drugs. “If you place the slime mold on a Petri dish where it has access to valerian root and access to food, it will choose the valerian root, and it will be to its detriment; it will often die as a result of that poor decision,” Keats says. The situation is a binary choice: hard drugs or no drugs.

The slime mold faced a gradient of valerian root, with the “drug” most concentrated at the center of the dish. RAINA MENDELSo the researchers asked: Given access to a gradient of valerian root across a Petri dish, where do slime molds situate themselves? The researchers think of the gradient as a drug spectrum: the center, where valerian is most concentrated, represents hard drugs; the middle of the Petri dish are the “gateway drugs” of moderate valerian concentrations; and no drugs are present at the rim of the dish. The investigators found that slime molds that started near the pure valerian root migrated outward along the gradient toward areas with lower concentrations of valerian, whereas those placed near the rim migrated less toward the center.

The “gateway drugs” of moderate valerian abundance appeared to pull the slime molds away from the pure valerian root to a greater extent than it pulled sober slime molds toward it. To Keats, these asymmetrical migrations suggest that gateway drugs do not lead to further drug use but, rather, serve as less-harmful alternatives to hard drugs.

In his role as consortium secretary, Keats has briefed officials at the United Nations, the Department of Homeland Security, and other relevant political bodies on the experimental results and what he views as their policy implications. For example, in a letter to Attorney General Jeff Sessions, Keats writes: “Preliminary results from the plasmodial research group suggest that cannabis and its chemical derivatives should be legalized by the United States government.” The Department of Justice has not yet responded.