Rockville, MD--If you could peer microscopically into the closest freshwater pond, you'd hesitate before dipping a toe. Amid the murky water, you'd probably notice an oddly furry, pear-shaped organism gliding along--and gobbling up everything in its path.

This tiny predator has a big name--Tetrahymena thermophila--and a big fan club among scientists, as a star organism for research into how cells work.

Scientists have now sequenced, assembled, and analyzed T. thermophila's macronuclear genome. Their work, reported in today's issue of Public Library of Science (PLoS) Biology, explains the organism's impressive versatility. Rather than dividing labor into several types of cells, as humans and other multicellular organisms do, T. thermophila divides its activities, either into different places inside a cell or by changing the cell over time. It is a master multi-tasker.

"This organism is a true generalist," says evolutionary biologist Jonathan A. Eisen, who led the Tetrahymena project while at The Institute for Genomic Research (TIGR) and is now at the University of California, Davis. "Whatever this unicell touches with its hairlike projections, it will try to eat. If it does not bump into anything, the organism will seek out food with diverse sensory systems. It can protect itself from radiation and other threats and also can fight back against competitors and predators. In short, versatility is its strength. Now, we can understand how this versatility works."

It takes plenty of genes. In fact, T. thermophila has roughly 25,000 genes--nearly as many as humans do. Although the organism is single-celled, it contains a genetic repertoire of seemingly more complex organisms. It shares, with humans and other animals, many genes and processes typically absent in single-celled organisms. That means Tetrahymena may be an ideal model organism for studies of the processes these genes encode.