Experiments suggest that infections could spread more rapidly in space

In 1970, astronaut Fred Haise got very sick on the Apollo 13 mission. Now, a group of scientists at NASA teamed up with biologists at Arizona State to study what happens to bacteria in space. One of the microbes they're studying is Pseudomonas aeruginosa, which is what made Haise ill. Now, the researchers have discovered that the zero-gravity environment causes some strains of bacteria to become more virulent.

"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," said Cheryl Nickerson, associate professor at the Center for Infectious Diseases and Vaccinology, the Biodesign Institute at Arizona State University (ASU) in Tempe . . . During the initial study in 2006, two bacterial pathogens, Salmonella typhimurium and Pseudomonas aeruginosa, and one fungal pathogen, Candida albicans, were launched to the station aboard space shuttles. They were allowed to grow in appropriately contained vessels for several days. Nickerson's team was the first to evaluate global gene and protein expression (how the bacteria react at the molecular level) and virulence changes in microbes in response to reduced gravity . . .

The initial study and follow-on space experiments show that spaceflight creates a low fluid shear environment, where liquids exert little force as they flow over the surface of cells. The low fluid shear environment of spaceflight affects the molecular genetic regulators that can make microbes more infectious. These same regulators might function in a similar way to regulate microbial virulence during the course of infection in the human body.

"We have now shown that spaceflight conditions modified molecular pathways that are known to be involved in the virulence of Pseudomonas aeruginosa," said Aurélie Crabbé, a researcher in Dr. Nickerson's lab at ASU and the lead author of the paper. "Future work will establish whether Pseudomonas also exhibits increased virulence following spaceflight as did Salmonella."

It seems that something about the way fluids behave in a freefall environment tricks the bacteria into thinking that they've found a nice place to reproduce - something like a human lung or gut. So they spread more quickly. Does that mean space is the ideal place for microbes to reproduce? That space plagues are the worst kind? A lot more testing is required to find out, but these results are completely fascinating to say the least.

Read more about the study via Arizona State and read the full scientific paper via PubMed