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participants, they reported fewer cold symptoms than were detected in medical exams.

The new study, which appears in the November/December Psychosomatic Medicine, replicates those results and rules out the possibility that psychological traits related to a positive emotional style, rather than the emotions themselves, guard against cold symptoms. Those traits include high self-esteem, extroversion, optimism, and a feeling of mastery over one’s life.

The latest data also show that among people with a consistently positive mood, well-being doesn’t simply reflect physical vigor. All volunteers entered the study in comparably good health.

In that project, Cohen’s team interviewed 193 healthy adults by phone each evening for 2 weeks. The participants reported their positive and negative emotions during that day. They then received nasal drops containing a rhinovirus or an influenza virus that causes a coldlike illness.

Each person was quarantined in a separate room and monitored for 5 or 6 days. Although a positive emotional style bore no relation to whether participants became infected, it protected against the emergence of cold symptoms. For instance, among people infected by the influenza virus, 14 of 50 (28 percent) who often reported positive emotions developed coughs, congestion, and other cold symptoms, as compared with 23 of 56 infected individuals (41 percent) who rarely reported positive emotions.

The extent of positive emotions, but not of negative ones, exerted a strong impact on the emergence of cold symptoms, Cohen says. His recent analysis of immune measures from volunteers in the 2003 study, published last March in Brain, Behavior, and Immunity, points to enhanced regulation of an infection-fighting substance, interleukin- 6, in people with positive emotional styles.

Cohen’s current study offers “an interesting twist” on the relationship between feelings and health, remarks psychologist Janice K. Kiecolt-Glaser of Ohio State University in Columbus. Other research indicates that negative emotions influence immune function and illness development more powerfully than positive emotions do, Kiecolt-Glaser says.

However, psychologist Barbara L. Fredrickson of the University of North Carolina at Chapel Hill notes that the new data agree with her work showing that to a surprising degree, positive emotions can bolster the immune system to improve health.

IN HOT WATER Deep undersea near the Axial volcano in the northeast Pacific, the seafloor releases jets of scalding water that carry unusual microbes, including nitrogen fixers.

Studies of the impact of mood on physical health need to account for both positive and negative emotions, Cohen holds. He points to preliminary data from other teams suggesting that among depressed people, a lack of positive emotions is a more accurate predictor of stroke than is the extent of their negative emotions. —B. BOWER

Hottest Fixer

Undersea-vent microbe sets nitrogen record

A spherical microbe from the weird world of hot-water ocean vents has trumped the nitrogen-processing powers of all organisms previously studied.

Like some soil microbes and bacteria living in pea plants and their relatives, the microbe known as FS406-22 turns plain nitrogen (N₂) into a form that other living creatures can use, explains Mausmi P. Mehta of the University of Washington in Seattle. However, FS406-22 does the chemistry at 92°C (198°F). That’s 28°C above the record set by the previous champ, a microbe collected from sea sediments near Naples, Italy.

FS406-22 is also the first nitrogen fixer identified in an undersea vent, say Mehta and her Seattle colleague John A. Baross. Vents differ in what forms of nitrogen are available in the water they release, says microbial oceanographer David M. Karl of the University of Hawaii in Honolulu. But if most of the nitrogen is the virtually inert N₂form, the activity of FS406-22

“would be of great ecological significance,” he says. Living creatures use nitrogen in complex molecules, such as DNA and proteins, and nitrogen shortages limit growth in some habitats.

Microbes with enzymes that work at the high water temperatures near vents might have “biotechnological potential,” says nitro-gen-cycle specialist Douglas Capone of the Oceanographic Laboratory at Villefranche in France. “There is a fair amount of research interest on thermally stable enzymes,” he says.

With the limited availability of input from the sunlit world, seafloor vents tend to harbor creatures that have novel chemistry. Mehta set out to find any vent organism that fixes nitrogen under those extreme conditions.

She and Baross pursued this quest for several years during a series of research cruises to the underwater Axial volcano in the northeast Pacific. Scientists on board sent down robotic collection vehicles with arms that poked into gashes in the seafloor. They brought back samples that “look like water,” says Mehta, but have a “nasty, rot-ten-egg smell.”

Mehta put vent-water samples into containers of various nutrient soups that only a nitrogen-fixing microbe could love. In hundreds of containers where the only nitrogen was in the N₂form, she ended up with nothing. In 2004, however, one batch of containers turned cloudy with a thriving microorganism that Mehta designated FS406-22.