NASA researcher Sharmila Bhattacharya studies fruit flies flown aboard the Space Shuttle Discovery in hopes of better understanding the effects long duration spaceflight has on humans. Photo Credit: John Rogers

Nearly one hundred fruit flies left the launch pad as eggs, hatched en route and landed at the International Space Station in larval form. Thousands made the return trip to Earth. Although living quarters were tight, huddled inside 10 Plexiglas containers the size of computer discs, the tiny flies with pin-sized brains, gorged themselves on auger, multiplied by the hundreds and morphed from larva into adulthood during their 13-day journey to space on shuttle Discovery in July, 2006.

Could these tiny pests, with a life expectancy of four to six weeks, teach humans something new? After all, scientists have already proven they are social animals, have memory, can be taught and avoid certain smells. And, about 61 percent of known human disease genes have a recognizable match in the genetic code of fruit flies.

NASA has been studying the effects of space travel for decades, often using fruit flies as their baseline because they are genetically similar to humans. Still, it is extremely hard to predict how gravity – or lack of it -- signals a gene to change its ways. But, it happens and the space agency wants to know why.

During missions, astronauts are exposed to a range of gravitational forces, and that will only increase with movement to the next phase of space travel as the nation sets its sights on the Moon and beyond, Mars. NASA says during a trip to Mars, an astronaut could feel several Gs (gravitational force) during launch, 0-g during interplanetary cruise and several more g’s descending to Mars with 0.38 g during their stay on the red planet. The questions remains, how are genes going to react to these changes? Will they develop in new or unexpected ways?

Researchers think they can unlock some of the secrets by sending fruit flies to space, studying their behavior and taking blood samples to see how weightlessness forces genes to alter their genetic expression. Previous studies have proven that when an astronaut gets sick in space, it is harder to get well. The human immune system doesn’t attack germs as ferociously as it does here on Earth. It has also been proven that astronauts’ bones weaken during long voyages and without lots of exercise, their muscles atrophy. And, in a 1999 study, scientists grew human kidney cells onboard the shuttle. More than 1,000 of the cells’ genes behaved differently, with some of them producing extra vitamin D receptors. A surplus of vitamin D can reduce the risk of prostrate cancer in men, which is a benefit.

Fruit flies as seen under the microscope in NASA's Life Sciences Lab at Kennedy Space Center in Florida. Photo Credit: John Rogers

“The experiment (this time) was their immune system,” Sharmila Bhattacharya, research scientist in the NASA-sanctioned project, said. “We are looking at changes (in the immune system) after a long time in space, to see if they have increased levels of proteins to fight infections.”

By experimental standards, 13 days is hardly enough time to consider a valid baseline, but in the case of the fruit fly, they reproduce quickly, so many generations can be studied in a short time.

The research team sent the flies to space in varying cycles of their brief lives. “The time spent in space is more than one-third of their life cycle,” Bhattacharya said.

The Ames Research Center team, located in Moffett Field, Calif., produced a batch of fruit flies – known as Drosophila Melanogaster -- for the controlled experiment. Half of the flies went to space while their counterparts stayed behind at a Kennedy Space Center laboratory. By coming from the same genetic “batch,” the flies had similar DNA makeup, thus keeping the baseline similar.

After the touchdown of the shuttle July 17, the research staff, including biology professors from the University of Central Florida and University of California as well as the Ames Center, worked for two weeks to extract blood from only the female test flies – both the space travelers and the homebound species. But before the blood was drawn, a small amount of a fungus was dusted on their food to expose some of the flies to possible infection. Researchers staggered the exposure at different stages in the flies’ lifecycle then checked to see how the immune system reacted in both sets of flies.

Bhattacharya said fruit flies were chosen because they are low maintenance and their immune systems are similar to humans. On day six, German astronaut Thomas Reiter fed them because the next generation of flies had been born, otherwise they were on their own.

This was the fruit flies home away from home during their 13 day visit to space. Photo Credit: John Rogers

Inside the lab at Kennedy Space Center, the flies were “put to sleep” through carbon dioxide leaks into the plastic container they lived in. Once asleep, the scientist would separate the females from the males – girls have less black on their behinds – underneath a microscope. Next a tiny slit would be made into the belly of the fly, and by pushing the tip of a blunt instrument across the body part, the blood, a clear substance, would be extracted. Just seconds after the flow of the gas stopped, the flies would wake up and start buzzing around, said researcher Oana Marcu.

“In a fruit fly, the blood is all over the body,” she explained. “They do not have veins so we don’t have to hit a certain place to get the blood sample and they won’t keep bleeding.’’

The team also took blood samples from the earthbound flies to compare the high and low levels of both sets. The results should show if the space flies produced higher levels of peptide proteins – used to fight infections -- in their blood.

“We anticipate that the stressful situation they were in will affect the immune system,” Bhattacharya said. “By using the fruit fly, its lifecycle is quicker so we can study an animal that develops most of its life in space.”

A second reason the group chose the fruit fly is, the immune system is simple to understand. This study, which only looked at the immune system and not the behavior of the fly in space, will be completed in about two years. Researcher Laura Higgins said the flies seemed fairly normal upon their return.

“They didn’t act weird or anything,” she said while drawing blood from the species last month. “They didn’t come back with two heads, but then neither do astronauts.’’

The results should give scientists vital clues about how extended time outside of Earth’s gravity stresses the human body, Bhattacharya said.

“Until we see the majority of the test results, we can’t draw any conclusions, but the global picture looks good.”
 she said from her office in California, in early September.

“We predict what we find will help humans better adapt in space.”

Believe it or not these are luxury apartment buildings for fruit flies. Upon their return to Earth, the frit flies were moved from their cramped flight quarters to these much more roomy digs. The liquid in the bottom is food. Photo Credit John Rogers	This is a close-up of a computer screen used by NASA researcher Sharmila Bhattacharya to examine the flies. Photo Credit: John Rogers