The title sounds like a crime novel on a dime-store shelf. But "An Invitation to Die" is quite literal in its meaning. And the prime suspect is very, very small.
Rice University evolutionary biologists reported in a paper published this week that the first cells to starve in a slime mold seem to have an advantage that not only helps them survive to reproduce, but also pushes those that keep on eating into sacrificing themselves for the common good.
The paper by Rice graduate student Jennie Kuzdzal-Fick and her mentors, David Queller and Joan Strassmann, Rice's Harry C. and Olga K. Wiess Professors of Ecology and Evolutionary Biology, appears in the online edition of the Royal Society journal Biology Letters. The paper's full title is "An Invitation to Die: Initiators of Sociality in a Social Amoeba Become Selfish Spores."
It helps to understand what Dictyostelium discoideum are, and how they behave. The single-cell organisms collectively known as slime mold live independently and feed on bacteria until the food runs out. When that happens, adjacent cells aggregate into a single slug and move as a slime-coated unit toward heat and light, which indicate the presence of a good place to form a fruiting body. At their destination, amoebas at the front sacrifice themselves, dying to form a cellulose stalk. Others in the colony climb aboard and become spores that sit on top, where small organisms disperse them to nutrient-rich places.
Common wisdom dictates that the first cells to starve would be the first to die. "Because they initiate aggregation into the social stage, we were interested in finding out what their reproductive fate was," Kuzdzal-Fick said. "For a lot of reasons, it would make more sense if the first cells to starve altruistically formed the stalk."
But that's not how it happens, and it took her months of detective work to track down the clues. Kuzdzal-Fick employed a complex sequence of r
|Contact: David Ruth|