Farming amoebae carry around detoxifying food

Five years ago, the Queller-Strassmann lab at Rice University, now at Washington University in St. Louis, demonstrated that the social amoeba Dictyostelium discoideum – affectionately nicknamed “Dicty” – can maintain a crop of food bacteria from generation to generation, giving these farmers an advantage when food is scarce.

Now, new research from the same team shows that these microscopic farmers also rely on their symbiotic bacteria to protect themselves from environmental toxins, a little-studied but increasingly clear role microbes can play for their hosts.

Research scientist Debra Brock led the new work, published April 20 in the Proceedings of the Royal Society B.

These amoebae are content to be loners when food is abundant, but when it’s depleted they come together in the tens of thousands to cooperate. They transform into a mobile slug that migrates in search of fairer conditions and then produces hardy spores to release into the environment and wait out the lean times.

The slug has a tiny pool of specialized cells, called sentinels, that protect it from pests and poisons by ferrying them away.

“The sentinel cells pass through the body, mopping up toxins, bacteria, and essentially serving as a liver, a kidney, and innate immune system and being left behind in the slime trail,” said Joan Strassmann, PhD, the Charles Rebstock Professor of Biology in Arts & Sciences.

Debra A. Brock, W. Éamon Callison, Joan E. Strassmann, David C. Queller. Sentinel cells, symbiotic bacteria and toxin resistance in the social amoebaDictyostelium discoideum. Proceedings of the Royal Society B: Biological Sciences, 2016; 283 (1829): 20152727 DOI: 10.1098/rspb.2015.2727

The social amoeba Dictyostelium discoideum has both solitary and communal life stages. As long as food is abundant, it lives on its own, but when food is scarce the amoebae seek one another out. Together they form a slug that migrates toward the light and then a fruiting body that disperses spores from atop a stalk. The fruiting bodies are pictured here. Credit: Strassmann/Queller lab