Scientists have been studying how spaceflight makes bacteria more virulent, in work that could have implications for the health of the Earthbound as well as astronauts.
They've been looking at an opportunistic pathogen known as Pseudomonas aeruginosa - the same bacterium that made astronaut Fred Haise sick during the Apollo 13 moon mission in 1970.
The scientists believe the research could lead to better vaccines and therapies.
"For the first time, we're able to see that two very different species of bacteria - Salmonella and Pseudomonas - share the same basic regulating mechanism, or master control switch, that micro-manages many of the microbes' responses to the spaceflight environment," says Cheryl Nickerson, associate professor at Arizona State University.
"We have shown that spaceflight affects common regulators in both bacteria that invariably cause disease in healthy individuals and those that cause disease only in people with compromised immune systems."
By studying the global gene expression patterns in bacterial pathogens like Pseudomonas and Salmonella, Nickerson's team learned more about how they react to reduced gravity.
During an initial study in 2006, Salmonella typhimurium, Pseudomonas aeruginosa and Candida albicans were launched to the station aboard shuttles, and were allowed to grow for several days.
"We discovered that aspects of the environment that microbes encountered during spaceflight appeared to mimic key conditions that pathogens normally encounter in our bodies during the natural course of infection, particularly in the respiratory system, gastrointestinal system and urogenital tract," says Nickerson.
Follow-on space experiments showed that spaceflight creates a low fluid shear environment, where liquids exert little force as they flow over the surface of cells. This affects the molecular genetic regulators that can make microbes more infectious.
"We have now shown that spaceflight conditions modified molecular pathways that are known to be involved in the virulence of Pseudomonas aeruginosa," says researcher Aurelie Crabbe. "Future work will establish whether Pseudomonas also exhibits increased virulence following spaceflight as did Salmonella."