Bacteria that cause food poisoning on Earth get stronger in space, says a team of researchers that sent dozens of carefully packaged vials of salmonella on a 2006 shuttle mission.
After 12 days in orbit, the shuttle bugs were nearly three times more deadly to mice.
The researchers, who are reporting their findings this week in the Proceedings of the National Academy of Sciences, were able to zero in on the protein that caused the increased virulence. They say their work may one day lead to a vaccine to protect against Salmonella typhimurium, or a new antibiotic to keep an infection in check - both in space and on Earth.
"It has tremendous potential," said Cheryl Nickerson, a researcher at the Biodesign Institute at Arizona State University.
In healthy people, food poisoning caused by salmonella bacteria isn't deadly, but it can be an ordeal. "It is never pleasant anywhere, much less where everything floats," Dr. Nickerson said in an interview yesterday.
While astronauts are generally very healthy, a number of studies have suggested that some parts of their immune systems don't work as well in space. Dr. Nickerson doesn't want to be alarmist, but stronger bacteria could be a double whammy, especially on long space flights like the one now being planned to Mars.
"It is an important concern," she said.
Food poisoning has never been reported on a space shuttle mission or on the International Space Station, Dr. Nickerson said, but a number of Russian cosmonauts have succumbed to gastrointestinal viruses.
In 1970, Fred Haise, part of the Apollo 13 crew, developed a severe urinary tract infection caused by an opportunistic bacterium called Pseudomonas aeruginosa.
Dr. Nickerson and her colleagues sent two other disease-causing bacteria up on the 2006 mission, including Pseudomonas aeruginosa. But there are no reports yet on whether they too became more virulent.
Why would bacteria become more robust in space?
Dr. Nickerson said there is evidence that fluids flow over the outer membranes of bacteria differently in low gravity, and that this may trigger changes. Fluid flows over bacteria in different ways in the human body as well - for example, in the bloodstream - but scientists don't know what impact this has on them. Dr. Nickerson's work suggests it might be important to find out.
She and her colleagues identified a protein, called Hfq, that appears to be responsible for the increased virulence of the space salmonella. This could be a target for a vaccine or a new antibiotic, she says.
For years, scientists have speculated about whether disease-causing microbes might mutate in space. This is the first experiment to see whether this is in fact the case, Dr. Nickerson says.
She and her colleagues compared the bacteria that went up on the shuttle Atlantis last year with vials that were kept at the same temperature and humidity at the Kennedy Space Center in Florida.
As well as injecting mice with either the stay-at-home or the space-travelling bacteria, they did a genetic analysis, and studied the proteins that both sets of micro-organisms produced. They found that space travel altered the way 167 genes functioned.
How far to the hospital?
Just as mechanical failures in space are nearly inevitable, so are physical "failures" in the human body. Some astronaut ailments are so common that they can be treated in-flight, while others, although more rare, can complicate a mission.
Motion sickness - usually some combination of sweating, dizziness, nausea and vomiting - is the most common, affecting between 67 and 75 per cent of astronauts as they enter space.
Skin, eye or respiratory tract infections were reported 13 times in Apollo missions and eight times in Skylab missions. Getting a "cold" in space is difficult to handle, especially because the nose can't drain in microgravity, resulting in the sinuses filling with more and more fluid.
Some of the more serious illnesses that have afflicted space missions include the following:
In 1987, after spending six months on Mir, Alexander Laveikin had to cut short his mission and return due to dysrhythmias, or irregular heart rhythms.
After Apollo 13's oxygen tank exploded, the command module lost all power and the three astronauts had to use the attached Lunar Module as a lifeboat. In addition to enduring freezing temperatures and dehydration (water was rationed to six ounces per person per day), all three had to wear their condom-style urinary catheters constantly. Astronaut Fred Haise became feverish and lethargic. A medical examination after their successful recovery showed that he had a urinary tract infection brought on by dehydration.
Source: the Mars Society