There are bacteria that blink on and off like Christmas tree lights and bacteria that form multicolored patterns of concentric circles resembling an archery target. Yet others can reproduce photographic images.
These are not strange-but-true specimens from nature, but rather the early tinkering of synthetic biologists, scientists who seek to create living machines and biological devices that can perform novel tasks.
"We want to do for biology what Intel does for electronics," said George Church, a professor of genetics at Harvard and a leader in the field. "We want to design and manufacture complicated biological circuitry."
While much of the early work has consisted of eye-catching, if useless, stunts like the blinking bacteria, the emerging field could one day have a major impact on medicine and industry.
For instance, Christina Smolke, an assistant professor at the California Institute of Technology, is trying to develop circuits of biological parts to sit in the body's cells and guard against cancer. If they detected a cancer-causing mechanism had been activated, they would switch on a gene to have the cell self-destruct.
Jay Keasling at the University of California is trying to take up to 12 genes from the wormwood tree and yeast and get them to work together in E. coli bacteria to produce artemisinin, a malaria drug now extracted from the wormwood tree.
Craig Venter, the maverick scientist who sequenced the human genome, wants to create microbes that produce hydrogen for use as fuel.
To be sure, scientists have been putting genes into bacteria and other cells for three decades. The term "synthetic biology" seems to include various activities, some of which are not altogether new.
"This has a catchy new name, but anybody over 40 will recognize it as good old genetic engineering applied to more complex problems," said Frances Arnold, a professor of chemical engineering at Caltech.
Some synthetic biologists say they will go beyond genetic engineering, which often involves putting a single foreign gene into a cell. The human insulin gene, for instance, is put into bacteria, which then make insulin for use as a drug. But there have been genetic engineering projects involving multiple genes, so the number of genes alone is not enough to define synthetic biology.
Rather, the difference seems more about mind-set. "We're talking about taking biology and building it for a specific purpose, rather than taking existing biology and adapting it," Keasling of Berkeley said. "We don't have to rely on what nature's necessarily created."
Also new is an engineering approach -- the desire to make the design of life forms more predictable, like the design of a bridge. That could be because many leaders of the field are not biologists by training.
Ron Weiss of Princeton is a computer scientist. Michael Elowitz of Caltech trained as a physicist, and Drew Endy of the Massachusetts Institute of Technology as a structural engineer. Endy and colleagues at MIT have started a Registry of Standard Biological Parts. The parts, called BioBricks, are strings of DNA that can perform certain functions like turning on a gene or causing a cell to light up.
In theory at least, these components can be strung together to build more complex devices, just as an electronic engineer might put together transistors, resistors and oscillators to build a circuit. Scientists at the University of California, San Francisco, and the University of Texas used some BioBricks to engineer bacteria so that a sheet of them could capture an image as photographic film does. The microbes were altered so that those kept in the dark produced a black pigment while those exposed to light did not.