Spotlife: Dictyostelium!

Copyright, M.J. Grimson & R.L. Blanton. Biological Sciences Electron Microscopy Laboratory, Texas Tech University

Dictyostelium discoideum, a.k.a. slime mold, has to be one of the coolest organisms ever. Sure, it looks like a tiny slug-fungus-plant, but it's so much more! This tiny organism has lessons to teach about cell signaling, cell movement, network formation, group selection, and even the evolution of multicellular organisms. And it's got one of the coolest life cycles of anything on earth.

Let's start from the beginning. Dictyostelium normally lives in soil and leaf litter as a single-celled amoeba. They look like most other amoeba you might find crawling around decaying matter in your backyard.

But when food becomes scarce, something weird starts to happen. The hungry amoeba start sending out waves of a common cell signaling molecule called cAMP. When the other amoeba sense cAMP in their environment, they know they'll soon run out of food too, so they start sending out cAMP too, and they head for the place where their fellow amoebas are hanging out. Pretty soon you have a whole mess of Dictyostelium sending out a ton of cAMP, and they all start moving towards the place where the signal is strongest: the center.

Now, you might ask, do they just all make a bum rush for the dead-center like 6-year-olds on a downed pinata? No. For reasons having to do with the wave-like nature of their signaling, they start moving around the central point in a psychadelic spiral:



Far out right? We're just getting started. Once the amoeba all get together, they form a long slug-like body and work together to inch along the ground until it senses light. Then the cells on one end differentiate to form a long stalk that pushes a few, lucky spore cells to the top. Then, the spore cells are released into the air, in hopes that they'll land somewhere where food is more abundant.

So that's Dictyostelium. It's unicellular and it's multicellular. It's a psychadelic spiral-maker. It's a slug, a stalk, and a spore. And it's totally awesome.