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The Hidden Life Of Legumes

Food factories in the making

The Australian Outback’s red-toned expanse features a vast vista of sky. But microbiologist Valerie Oke isn’t looking up. Instead, she has her eyes on the vegetation that mottles the landscape. The soil here must be nitrogen-poor, she thinks. Because, boy, there are a lot of legumes.

Oke, a Pitt assistant professor of biological sciences, came upon the plain of legumes while on a recent vacation in Australia’s great wilderness. She isn’t a botanist and readily admits she doesn’t have a green thumb: “I have a garden at home that my husband cares for. I have nothing to do with it.” But the work under way in her University lab has everything to do with green-thumb gardening on a grand scale, and legumes are key to her success.

Her research focuses on nitrogen, which is essential to life because it’s a
component of DNA and proteins. Even though almost 80 percent of the air is nitrogen, no multicelled organism is able to use nitrogen gas directly. Instead, the gas must be ingested from food or, in the case of most plants, from the soil. In places with nitrogen-poor soil, plants don’t grow very well, if at all. This is one reason a lot of land is unsuitable for agriculture without the addition of vast amounts of manmade nitrogen fertilizers.

But legumes are different.

Plants such as alfalfa, clover, peas, beans, peanuts, and soybeans are part of the legume family, which has fascinated researchers like Oke for years. Legumes interact with a soil bacterium called rhizobium. The bacteria enter into the plants’ roots, which form nodules where the bacteria live. Then the bacteria convert nitrogen gas into ammonia, which is a usable form of nitrogen. In other words, the bacteria are nitrogen-rich factories within the plants themselves. In return, the bacteria get nutrients from the plants. It’s a beneficial exchange.

Biologists have known about this cooperative process—or symbiosis—for a long time, but many of the specifics have yet to be understood. “We don’t know the details of how the bacteria physically get inside the plant, what controls the process, what sort of environment the bacteria live in inside the plant, and how the plant forms a nodule,” says Oke. Her laboratory is pursuing the genetic factors involved in this symbiosis to better map the complexities of the mutual exchange between these bacteria and plants.

Oke’s research goes well beyond simple curiosity, of course. If researchers can understand the process, perhaps they can improve or even replicate it. “The big hope is for agriculture,” she says. “Only legumes perform this kind of symbiosis. The real pie-in-the-sky idea is to take a major crop like rice, which is not a legume, and have it interact with bacteria to get its nitrogen.”

The impact of such a breakthrough would be immense. Soil quality would become less important, resulting in easier farming. There would be no need for nitrogen fertilizer, decreasing the global consumption of natural gas.

(Oke cites 1990s data indicating that the artificial synthesis of ammonia for nitrogen fertilizer amounts to 5 percent of natural gas consumption worldwide.) There would be an ecological boon as well: Fertilizer runoff has been blamed for excess algae growth and “dead zones” in coastal waters.

Although Oke thinks such a breakthrough would be unlikely, she is more optimistic about other possibilities. “Improving the current symbiosis would be more realistic than transferring that process to other plants,” she says, laying out a scenario in which farmers first plant their lands with souped-up legumes that would operate like nitrogen factories, enriching the soil for future crop rotations.

“If we could boost the natural ammonia production to more than what the legumes need and get that into the soil…” Oke trails off, perhaps thinking of an Australian Outback with even more legumes than she has encountered in her travels there. “The person who does that would win a big prize.” —Bo Schwerin

Footloose

Giving injuries the slip

Wearing headphones, a 67-year-old woman listens contentedly to Strauss’ “On the Beautiful Blue Danube” while strapped in a harness in the basement of Benedum Hall. The lights are dimmed.

An undergrad bioengineering student kneels on the floor behind her. With surgical gloves on his hands, the student spreads a thin sheet of slippery glycerol on the vinyl floor. Facing the room’s cinder block wall, the woman can’t see him; she can’t hear anything, either, except the lilting waltz music.

Then another student gently removes the headphones from the woman’s ears and asks her to turn around and walk the length of the room. Eight meters right down the center, like a model on a catwalk.

Everyone in the room waits—and watches—to see what will happen. The green eyes of eight high-tech cameras also follow Carol Lydon as she takes her first steps forward.

“We don’t want her to be aware of the slippery condition,” says Rakié Cham, codirector of the Human Movement and Balance Laboratory in Pitt’s School of Engineering. She watches Lydon step forward on the slicked-up floor. Since the beginning of the lab’s research on slips and falls about seven years ago, researchers and students have witnessed about 700 people slip in this controlled space. “Don’t worry,” assures Cham, who is also an assistant professor of bioengineering. “The harness will catch her if she actually falls.”

Lydon’s foot makes contact with the glycerol-smeared tile. Infrared motion detectors are ready to record even the slightest movement through 79 small reflective markers attached to her body. But she doesn’t slip. Not this time.

Pitt is at the forefront of slip-and-fall research, with one of only a dozen such labs worldwide. Each year, one in three people older than 65 have a serious fall according to federal government statistics. U.S. Department of Labor statistics estimate that more than a quarter-million workers suffer fall-related injuries annually that force them to take time off.

The lab, which has received support from the National Institutes of Health and others, contains more than $500,000 in special equipment, including a 3-D motion-analysis system and a Biodex strength-measurement machine. In addition to studying the slips and falls of the elderly, the lab also conducts gait research with pregnant women and people who have mobility impairments, mental health problems, and/or balance disorders.

Lab manager April Chambers shows a video of a less-fortunate walk Lydon took during a past experiment: In this version, Lydon’s foot loses grip and takes a short skid before she recovers with the other foot.

Simultaneously, the monitor depicts a computerized stick figure created by the reflective markers, a 3-D connect-the-dots figure of a human moving through a matrix. It is an easy way to see clearly the exact body joints that are affected by the slip.

“We’re looking at postural control and what it is that makes some people fall and some people not fall,” says codirector Mark Redfern, a professor of bioengineering, industrial engineering, and otolaryngology. “The hope is to find ways to prevent accidents from happening. This research could lead to different kinds of strength and speed training, and it could also have implications for environmental design.”

After the experiment, the fluorescent lab lights are switched back on, and somebody begins vacuuming and mopping the glycerol. Lydon takes off her pair of lab-issue Baytown PVC-soled shoes, and a student returns the pair to a shelf of dozens exactly like it—ready to be used by the next fall guy or gal. —Taha Ebrahimi

Breakthroughs in the Making


Serious Matter

Not ones to settle for manipulating ordinary forms of matter to achieve breakthrough scientific results, Pitt researchers have created their own. The entirely new substance—though called a polariton superfluid—is solid, yet slowed down and trapped within it are energy particles known as polaritons. Developed by David Snoke, a Pitt physics and astronomy professor, and graduate students Ryan Balili and Vincent Hartwell, the new form of matter combines the traits of electrical superconductors with those of lasers. Energy passing through the substance produces a pure beam of light more energy efficient than a laser, and the superfluid may eventually be used to develop new methods for sending optical signals through solid matter.

Beating Diabetes

In theory, the mice scrambling about the cage in William Ridgway’s lab should be quite ill. But remarkably, they all exhibit perfect health, and Ridgway has achieved a major success in the fight against diabetes. Ridgway, assistant professor of immunology in Pitt’s School of Medicine, and his team have developed an antibody treatment process that prevents diabetes from occurring in mice. The positive results indicate that a similar process could eventually be developed to help prevent the disease from occurring in humans.

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