Research Stories

by Margaret Coulombe

Color-enhanced scanning electron micrograph showing Salmonella typhimurium (red) invading cultured human cells: Photo courtesy of Rocky Mountain Laboratories, NIAID, NIH

The technology created by NASA scientists and engineers has done plenty to help humanity over the past five decades. All that brainpower and technical know-how has spawned and improved satellites. It has also led to the creation of flat-screen televisions, robotic wheelchairs, water purification systems, and cell phones. Could it now also hold the key to what ails us here on Earth?

Cheryl Nickerson has bet her career on it. Nickerson is an earthbound microbiologist at Arizona State University. She also is an associate professor in the School of Life Sciences and researcher in the Biodesign Institute at ASU. Her NASA-funded research supports the development of innovative experimental models for infectious disease and drug development, on Earth and in space.

Nickerson wants to transform our understanding of the forces that shape nasty little pathogens and their ability to cause disease.

"Those tax dollars we invest in NASA's manned space programs propel new product discovery that impacts our lives on a daily basis, including advances in health and medicine," Nickerson says. "So the fact that we have the potential to provide novel cures and therapeutics to treat infectious diseases as a result of the manned space program should come as no surprise."

It was a natural leap for Nickerson to look to space and beyond the bounds of Earth to ask new questions about disease. The ASU scientist qualified as an astronaut candidate finalist in 2004.

Past studies have shown that microbial contamination presents a real health threat in space, just as on Earth. The presence of disease-causing microorganisms aboard spacecraft is well documented. Infectious disease events have occurred in flight. For example, a crewmember on the ill-fated Apollo 13 mission to the moon suffered a debilitating urinary tract infection.

The close quarters aboard both the Space Shuttle and International Space Station (ISS) can be a factor leading to sickness and infection. So is the recirculated water and air. Crew members from different countries can also lead to problems. The people carry microbes native to their geographical locations. All are factors that increase the potential for exposure to infectious pathogens.

Scientists know that spaceflight also weakens the immune system, Nickerson says. There are reports of increased microbial resistance to antibiotics during spaceflight. In fact, according to NASA, approximately 25 percent of all Space Shuttle missions have had at least one crew member affected by a minor infectious illness.

Other big questions remain unanswered about how the pathogens themselves are affected by space travel:

• Does outer space affect their disease-causing potential?


• Do pathogens behave in the same way in space as on Earth?

Nickerson is one of the first to look for answers to these questions. She uses ground-based analogues of spaceflight. The main tool for this work is called a rotating wall vessel bioreactor (RWV). She also is translating the work into true spaceflight experiments on board the Shuttle and ISS.

How did Nickerson's "out-of-this-world" thoughts about science and pathogens first take flight? She says that she always knew she would become a scientist. She credits her parents for encouraging her intellectual curiosity.

"I always wondered how things worked. I took them apart—though I didn't always put them back together correctly," Nickerson explains. "And I grew up reading the books in my father's extensive science library—I was hooked."

Nickerson's father, Max, is one of the world's leading authorities in vertebrate zoology and herpetology. He is curator of the Florida Museum of Natural History at the University of Florida in Gainesville, and an ASU graduate.

Years of family nature walks also helped. The Nickersons hiked deserts, forests, and mountains. Conversations about what flora and fauna were native to those areas left the young scientist-to-be with a great respect for nature. "I also have one heck of a leaf and rock collection," she laughs.

Most importantly, Nickerson credits her family for not biasing her decision-making or career choices.

"They wanted me to choose a career that made me happy in life and to be the best that I could be at it," Nickerson recalls. "They told me that there was nothing that I couldn't do in life. They never placed limitations on my creative abilities, either in or out of the classroom."

The ASU scientist has gone on to develop a multitude of interests. She is an avid sports car enthusiast, participates in team sports, does strength training, and collects antiques. But it is science that provides her with the thrill of discovery.

"There is nothing else like it," she says. "Finding something new that no one else has found—that is just so exciting!"

Nickerson claims that research is what she "lives, sleeps and eats for." She sees the possibility of "providing a piece of the puzzle to advance human health."

Cheryl Nickerson

Four studies designed by Nickerson and her colleagues have now flown on the Space Shuttle and the International Space Station. The most recent experiment went up on Atlantis Shuttle Flight STS-115 (12A) in September 2006. Tests were conducted on four microorganisms, including Salmonella, a common pathogen that causes food poisoning.

"Our results show that space flight changes the disease-causing potential of some pathogens. For example, it made Salmonella better able to cause infectious disease. And it caused problems at lower doses. In other words, it became a more potent pathogen," Nickerson says.

The finding is important. The combination of an immunocompromised astronaut with a pathogen that is more virulent could have a significantly negative impact on crew health and mission success.

"In addition, we found that spaceflight globally alters the gene expression profiles of these pathogens as well as their cellular structure," Nickerson explains. The group also identified a likely master regulator involved in the response of these cells to spaceflight.

"This could be an important development," she says. "We want to better understand at the molecular level how spaceflight affects the biology of living cells, both microbial and human. We also want to know how to translate that understanding to the clinical bedside to advance human health on Earth," Nickerson adds.

What changes can make a bad bug worse?

Nickerson has done plenty of ground-based laboratory work. She has shown that Salmonella better resists being killed by stresses relevant to those that it encounters during infection in the host. Those stresses include heat stress—moving from outside to inside the body. Acid stress relates to the condition inside the stomach. Osmotic stress refers to changes in the water and salt concentration.

The presence of macrophages is also important. Macrophages are part of the immune system. They are one of the human body's early defense mechanisms against infection.

Nickerson says that these visible changes are reflected in the altered gene expression profiles of Salmonella during growth in the ground-base RWV bioreactor. They also are seen during true spaceflight. She found alterations in more than 160 genes. Many of those genetic alterations enhance the ability of the bacteria to cause disease.

Nickerson says that understanding the molecular effects of mechanical stressors on living cells is also important. Mechanical force is an important underlying cause for many different kinds of human disease. It can lead to cardiovascular disease, stroke, diabetes, cancer, and osteoporosis.

"We know there is a link between disease and mechanical forces," Nickerson explains. "But we need to know the molecular mechanisms involved. That will help us to develop new ways to treat and prevent disease."

Nickerson's excitement is infectious. The potential impact of her ASU group's findings could advance the prospects for improving human health on a global basis.

"You need to make this world a better place when you leave—no matter what your field is—and hopefully this is what we are doing," says Nickerson.

Will she achieve her goals? Perhaps the Kennedy Space Center bumper sticker on her wall says it best: "Failure is not an option."

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Cheryl Nickerson's work is supported by NASA, National Institutes of Health, and the Department of Homeland Security.

Listen to a podcast with the scientist at: http://askabiologist.asu.edu/podcasts/.