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SCIENCE & SPACE

Fruit flies might help astronauts thrive on long missions

Humans, 'golden bug' share many traits

By Marsha Walton
CNN

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Fruit flies, like humans have immune systems to keep them healthy.

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(CNN) -- Name: Drosophila melanogaster -- a.k.a common fruit fly.

Occupation: scientific worker.

Employed by: NASA, aboard the shuttle Discovery and at Kennedy Space Center.

Job Objective: Unlock secrets of immune systems to help prepare space travelers for long-term trips to the moon and Mars.

Fruit flies don't have resumes, but if they did, a few hundred would have work histories that are out of this world.

About 150 fruit flies and additional fruit fly eggs were included in the payload of the space shuttle Discovery for its just-completed, 5.3-million-mile mission. (Full story)

The insects' "flight experience" may help provide insight about the human immune system for future long-term space flights.

"Fruit flies serve as a great model of the human immune system," said Deborah Kimbrell, associate research geneticist in the department of molecular and cellular biology at the University of California at Davis.

Kimbrell is heading a research team that includes scientists from the NASA Ames Research Center, the University of Central Florida, Rice University and the University of Nevada-Las Vegas.

"When our funding started in 2004, the experiments were here on earth, so all that could be studied were the effects of hyper-gravity [additional gravity] on fruit flies. This experiment is going in the opposite direction, focusing on negative gravity. We have had interesting results when you increase gravity, and we will see what happens conversely," Kimbrell said.

Drosophila melanogaster, sometimes known as the "golden bug," is the tiny workhorse of scientists worldwide. The insects are good for study because they reproduce quickly, have a short life span and are "low maintenance."

Astronauts aboard Discovery only had to change the flies' food trays, a gelatin-like sugar mixture, one time during the flight.

Fruit flies go from egg to adult in 10 days, so the eggs loaded aboard Discovery should be young adults after its 13- day mission. The life span of the fruit fly is about 60 days.

There are still many questions about how the immune systems of astronauts react to weightlessness, or microgravity, in space.

While flies have a simpler immune system than humans, Kimbrell said the mechanics in the genes of both species are very similar, and because so much is known about the Drosophila genes, each one can be studied.

Still many mysteries about humans in space

"Every time you fly in space you are an experiment," said Dr. Scott Parazynski, NASA astronaut, physician and veteran of four shuttle flights.

Parazynski said there's already good information about lengthy space missions, including data from Russian space explorers. Cosmonaut Valeri Poliakov spent 438 continuous days on the MIR space station.

"The prices you pay are in muscle and bone integrity, but we've already learned some good countermeasures," he said.

Parazynski has helped design exercise equipment for use in long space flights. He's also an expert in space physiology and human adaptation to stressful environments.

But he says, a lot more needs to be learned before humans can attempt two-and-a-half or three-year missions to the moon or Mars. In addition to the reactions of the human immune system, some of the biggest questions involve exposure to radiation, "and the psychological challenge of being away from the home planet for three years," Parazynski said.

Laurence von Kalm, associate professor of biology at the University of Central Florida in Orlando, said observations of the fly immune systems could provide a good idea of what the human response might be.

"The primary question being asked is whether the immune system is compromised from prolonged space travel," said von Kalm.

To get that answer, both the high-flying fruit flies from Discovery and a control group at the Kennedy Space Center will be infected with fungus and bacteria. Over the next few weeks scientists will compare the responses of the two groups' immune systems, including tests such as blood cell count and blood clotting ability.

The control group of flies on earth had the same diet, temperature and humidity as the environment aboard the space shuttle.

"One thing is pretty well-established from short-term flights, like we have done over 100 times on the shuttle," said Johnson Space Center microbiologist Duane Pierson. "Clearly the immune system is not a major problem."

But, he added, it's a great leap from a two-week mission to one that lasts more than two years.

While scientists hope to gain a lot of knowledge from the fruit fly experiment, it may be one of the last experiments of its type for a while. NASA has cut funding for virtually all life science experiments aboard the shuttle, concentrating instead on the much-delayed construction of the international space station.

"I'm really lucky this project got spared, it's really a shame NASA has these cuts," Kimbrell said.

NASA microbiologist Pierson says physiology studies for long-term space flights will continue on earth.

"We can get a lot of productivity from ground-based studies," he said. That includes environments ranging from bed rest studies, to stress experiments in Antarctica, to work in NASA's undersea laboratory, Aquarius, off the coast of Florida.

CNN's Matthew Abshire contributed to this report

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