They found that as viscosity increased, the cilia used for swimming slowed. Doubling the viscosity slowed the movement of cilia by about half. But that wasn't true for the oral groove cilia; they barely slowed at all when the viscosity changed. At seven times the viscosity of water, the oral groove cilia slowed by only about 20 percent.
Morphologically, the two sets of cilia appear to be basically identical. That means the differences in their motion must come from the motors that drive them, the researchers say. Now that they have isolated two different motor behaviors in the same organism, researchers might be able to look at what factors drive those differences.
"Now we have these two motors in the same cell that we can contrast," Valles said. "Do they have different molecules available to them or different concentrations of molecules that drive their movement? Those are the kinds of questions we're looking at."
Those questions will take a bit more study. To help out, the physicists have enlisted the help of Brown biologist Anita Zimmerman. "We're hoping to learn how to hold on to paramecia so that we can watch them more carefully under different treatments with different chemicals or flow patterns," Valles said.
This most recent study has helped lay the groundwork for that future work, which could help explain how these tiny fibers came to be so adaptable.
"Biologists refer to [cilia] as a 'highly conserved organelle' because they turn up in so many different organisms and they do this widely varying stuff," Valles said. "We're hoping this might lift the lid a little and help us understand how they do it."
The research was supported by the National Science Foundation. Thomas Powers, professor of physics and engineering, was an author on the paper along with Jung and Valles.
|Contact: Kevin Stacey|