Along with the six-member crew, space shuttle Atlantis, scheduled for liftoff this Sunday, will be carrying some very small passengers to the International Space Station: three common microbes.

Scientists plan to study the ability of Salmonella typhimurium, Pseudomonas aeruginosa and Candida albicans, all microbes identified as potential threats to the health of space crews, to adapt to microgravity and to infect astronauts in the space environment.

Such understanding will help to evaluate risks for longer-duration missions when astronauts will be far from the medical luxuries of Earth.

"Our microbe experiment will be the first to investigate the effects of spaceflight on the disease-causing potential and gene expression profiles of disease-causing microbes," said the experiment's principal investigator Cheryl A. Nickerson, a researcher at the Biodesign Institute at the Arizona State University.

Less immunity

Studies have shown that spaceflight weakens the immune system of humans and animals. Additionally, with longer missions where water and air will be recycled and contamination becomes a risk, astronauts could be even more vulnerable to infections caused by these microbes:  

  • Salmonella typhimurium, are rod shaped bacteria known to cause Salmonellosis. Symptoms of this infectious disease include nausea, diarrhea, and fever. The illness can become much worse for those with weakened immune systems.
  • Pseudomonas aeruginosa, a potential water contaminant on spacecrafts, was responsible for a crewmember's urinary tract infection aboard the Apollo 13 mission.
  • Candida albicans, is a naturally occurring yeast in the human body and can overgrow if microbial communities are altered in space causing yeast infections and oral diseases.

"Spaceflight has been shown to induce key changes in both human and microbial cells that are directly relevant to infectious disease, including changes in immune system function, microbial growth rates, antibiotic resistance, and cell surface properties," said Nickerson.  "It is exciting to think of the potential benefit that research in space holds for translation to the clinical bedside by providing a better understanding of how pathogens cause disease that will lead to new ways to treat, prevent and diagnose infectious disease."

Raising microbes

The microbes will be flown in self-contained chambers activated by the astronauts. A crewmember can turn a hand crank to release the growth media onto the culture media.

The microbes will be allowed to grow for 24 hours in ambient temperatures before the astronauts stop the procedure.

"This experiment requires only the minimum of space shuttle resources, but it has the potential to greatly advance infectious disease research in space and on the ground," said the experiment's project manager Steven Hing, from NASA Ames Research Center. Because the microbes will be contained in hardware that provides three levels of containment, they will pose no threat of exposure to the astronauts.

Once the shuttle lands on Earth, some of the samples will be examined for disease causing potential while the rest will be frozen.  Differences in growth rates, genetic changes, and their ability to infect will be studied. This knowledge can advance the treatment of infectious diseases in space and on Earth.