On the horizon

All charged up over bacteria

Two scientists from the University of South Carolina have given new meaning to the phrase "bug juice." In their hunt for pollution-munching bacteria to clean water laced with toxic chemicals, they found one that cleans with a bonus: It makes electricity while it noshes.

The bacterium, Desulfitobacterium, or "Des," is common in freshwater ponds. While other forms of bacteria have been able to generate electricity while treating sewage wastewater, scientists were surprised that Des, already known to eat toxic materials, generated electricity at all. Oddly, it did so while in its dormant, spore stage. Because spores are so hardy, researchers Charles Milliken and Harold May suggest that Des might one day power devices that must endure long periods in hazardous conditions before being activated. They described their work this week at the American Society for Microbiology annual meeting in Atlanta.

Other researchers are now developing bacterial batteries for small devices such as cellphones. Some of these batteries may hit the market as early as next year.

What pumps methane into Titan's atmosphere? That's one question planetary scientists want to answer as they study Saturn's most famous moon. After reviewing images from the Cassini spacecraft, an international team is proposing in Thursday's edition of the journal Nature that plumes of ice or slush well up from the moon's interior, break through the surface, and then release methane into the wind. The proposal isn't new. But images showing that the moon lacks methane oceans have given it fresh legs.

The methane surrounding Titan has to be replenished somehow. If it weren't, the gas would vanish over the course of 10 million years or so, broken down by the feeble sunlight reaching it. Instead of a vast sea, the images show changes in reflected light that suggest differences in terrain. In addition, the moon's surface is relatively smooth; its lack of craters suggests that the crust is periodically refreshed. Finally, the group spotted a circular formation nearly 19 miles across; something researchers have never seen on any other icy moon. They suggest that the structure represents a plume of methane-rich ice working its way to the surface and forming a dome.

There will be no human clones this century because the work is dangerous, complicated, and unethical, the South Korea scientist at the forefront of stem-cell research and cloning technology said Tuesday.

"I don't think we will have any chance to meet a cloned human being within the next 100 years, at least," said Woo-Suk Hwang, the head of a team of South Korean scientists who cloned the first human embryo to use for research.

During a panel discussion, Dr. Hwang denounced human cloning as "not ethical" and "technically impossible."

Soil may play a larger role in creating smog than previously believed.

Researchers from the University of Washington, the Harvard-Smithsonian Center for Astrophysics in Massachusetts, and Dalhousie University in Canada examined satellite images to track global changes in nitrogen oxides in 2000. Those gases come from forest fires, soils, and the burning of fossil fuels. Mix nitrogen oxides with natural or man-made hydrocarbons and sunlight, and you get smog. Of the 44 million metric tons of nitrogen pumped into Earth's atmosphere each year, soil's contribution was thought to be small. But the team found that natural soil processes contributed 22 percent of the nitrogen oxides, some 70 percent higher than previously believed.

The team found that emissions of nitrogen oxides from soil were heaviest in Africa's Sahel region and in the northern hemisphere's mid-latitudes. In the Sahel, the biggest pulse came at the onset of the rainy season, which jump-starts soil bacteria into manipulating nitrogen. Likewise, in the northern hemisphere, bacterial activity kicks in after a long winter's nap.

The team suspects fertilizer use may also turbocharge soil bacteria in the north. The results are in a recent edition of "Faraday Discussions," a journal published by Britain's Royal Academy of Chemists.