Worm genome offers clues to evolution of ...( The genome of a humble worm that din...)

The genome of a humble worm that dines on the microbial organisms covering the carcasses of dead beetles may provide clues to the evolution of parasitic worms, including those that infect humans, say scientists at Washington University School of Medicine in St. Louis and the Max-Planck Institute for Developmental Biology in Germany.

In a paper published in the current issue of Nature Genetics, the researchers reported finding some surprises as they have decoded the genome of the worm, a tiny nematode called Pristionchus pacificus.

"We found a larger number of genes than we expected," says Sandra Clifton, Ph.D., research assistant professor of genetics and a co-author of the paper. "These include genes that help the worms live in a hostile environment, the result of living in and being exposed to the byproducts of decaying beetle carcasses, and others that also have been found in plant parasitic nematodes. The genome supports the theory that P. pacificus might be a precursor to parasitic worms."

Scientists estimate there are tens of thousands of nematode species. The worms are typically just one millimeter long and can be found in every ecosystem on Earth. Parasitic nematodes can infect humans as well as animals and plants.

One nematode in particular is well known in scientific circles: Caenorhabditis elegans has long been used as a model organism in research laboratories. Its genome sequence was completed in 1998 by Washington University genome scientists working as part of an international research collaboration.

Unlike C. elegans, which lives in the dirt, P. pacificus makes its home in an unusual ecological niche: it lives together with oriental beetles in the United States and Japan in order to devour the bacteria, fungi and other small roundworms that grow on beetle carcasses after they have died. While the beetles are alive and the nematodes' food source is scarce
'/>"/>