Researchers from the Berkeley and San Francisco campuses of the University of California have now discovered how the nematode C. elegans senses oxygen levels in order to steer clear of surrounding areas that are too low or too high in oxygen.

In the process, the researchers also discovered that the worm doesn't like as much fresh air as people thought. While nematodes grown in laboratory Petri dishes are kept at the same oxygen concentration humans breathe in ambient air - 21 percent - nematodes appear to prefer only 6 percent oxygen.

"It was totally unexpected that they would actually prefer 6 percent. We don't know why, though it probably gives them some survival advantage," said Michael A. Marletta, professor of chemistry and of molecular and cell biology at UC Berkeley, and a faculty scientist at Lawrence Berkeley National Laboratory (LBNL). "And the bordering and clumping that worm experts refer to as social behavior is really the worms, in an artificial setting like a Petri dish, trying to get to an area of 6 percent oxygen, which they like. It's a laboratory phenomenon."

Bordering and clumping is a peculiar behavior in which worms cluster around the border of the Petri dish instead of spreading evenly around the surface. Marletta and his colleagues, members of the California Institute for Quantitative Biomedical Research (QB3), determined that the bacteria the worms feed on are at a higher density around the border of the dish, consuming oxygen along with the worms. Apparently, when oxygen levels are high, the worms pile onto the densest clumps of bacteria, because that's where oxygen levels are lowest.

"The swarm of worms and density of bacteria together lower the oxygen concentration in that immediate envi
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Contact: Robert Sanders
rls@pa.urel.berkeley.edu
510-643-6998
University of California - Berkeley
8-Jul-2004