15 July 2004
Every breath you eat
A study of oxygen detection in the roundworm Caenorhabditis elegans
reveals a surprising connection between oxygen detection and feeding.
C. elegans lives in soil, where oxygen tension varies sharply,
so is responsive to small changes in oxygen concentration. The worms prefer
to live in atmospheres containing 2–12% oxygen (air is 21% oxygen
by volume). The avoidance of low oxygen tension is well known, but the
discovery of an upper limit of oxygen tolerance is new. Oxygen detection
is shown to depend on GCY-35, a haem-containing guanylate cyclase, which
also happens to be regulated by oxygen. This dual function comes into
play when worms exhibit a stereotypical behaviour known as 'social feeding'.
When oxygen concentrations exceed a certain amount, worms gather together
to graze bacterial lawns. Why should high oxygen trigger this behaviour?
The answer, it seems, is that these thick lawns of bacteria consume oxygen
more quickly than oxygen diffuses through the lawn, lowering oxygen concentrations
to more comfortable levels.
Oxygen sensation and social feeding mediated
by a C. elegans guanylate cyclase homologue
JESSE M. GRAY, DAVID S. KAROW, HANG LU, ANDY J. CHANG,
JENNIFER S. CHANG, RONALD E. ELLIS, MICHAEL A. MARLETTA & CORNELIA
I. BARGMANN
Nature 430, 317–322 (2004); doi:10.1038/nature02714
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