Amoeba farmers grow their own food

Certain kinds of amoebae carry a cache of bacteria that will be grown to feed their newly-hatched offspring. That sounds a lot like farming!

Commonly known as slime molds, amoebae of the species Dictyostellum discoideum, nicknamed “Dicty” by the people who study them, live in garden soil and moist leaf litter. In a recent press release, scientists at Rice University reported that about a third of these amoebae practice what appears to be a rudimentary form of agriculture.

Dicty have an unusual life cycle. In the soil, they live as single organisms feeding on bacteria. But when the supply of bacteria in their vicinity is depleted, they have to move on. To do that, they aggregate into a large colony, known as a “slug,” about 2 to 4 millimeters in length, and migrate to greener pastures. At its new home, the slug undergoes a final transformation, growing into a stalk that holds a “fruiting body” containing spores. When conditions are warm and moist, these spores will hatch into a new generation of amoebae.

Dictyostelium life cycle. Image Credit: Tijmen Stam, Wikimedia Commons

Scientist Debra Brock at the microscope, peering at amoebae. Image credit: Scott Solomon

Debra Brock, a graduate student at Rice University, discovered that some Dicty sequester certain strains of bacteria for later use. Those bacteria are later released with the slug’s spores, seeding the new environment with bacteria that will grow to feed the newly-hatched amoebae.

This ability to save bacteria for future cultivation gives the farmer amoebae an edge over non-farmers of the same species, allowing them to live in areas that originally had little food. As a result, farmer amoebae don’t need to migrate as far as the non-farmers.

The scientists are continuing their research, trying to determine the genetic differences between farmer and non-farmer amoebae. And, strangely, they’ve also observed that some types of bacteria picked up by the Dicty farmers are not consumed as food, perhaps serving a yet-unknown purpose.

“Fruiting bodies” discovered in amoebae collected in Virginia and Minnesota. Image credit: Scott Solomon.

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