Salmonella likes it in orbit, and not just for the view.

According to research conducted on the International Space Station (ISS), the effects of microgravity trip a switch in the bacterium that makes it much more virulent. The findings, which are to be published in PNAS Online Early Edition suggest astronauts could be at greater risk of developing infections on long space flights.

Cheryl Nickerson and colleagues at the Centre for Infectious Diseases and Vaccinology, Arizona State University, sent up flasks of salmonella on the STS-115 mission to the ISS. They wanted to discover whether or not spaceflight would affect gene expression and the disease-causing potential of a microbial pathogen.

The flask stayed aboard the ISS for just 24 hours. According to The Times, the experiment was kicked off by astronaut Heidemarie Stefanyshyn-Piper. She opened a chamber in the flask that gave the bacteria access to a growth medium. After 24 hours, part of the sample was drenched in chemicals that would preserve the state of gene expression. The rest was given more of the growth media, and allowed to continue growing.

Meanwhile, back at Arizona State University, Nickerson was running a parallel control experiment, replicating all but the microgravity conditions on the space shuttle.

Once the flask was returned to Earth, Nickerson analysed the bacteria for changes in gene and protein expression levels. Compared to Earth-bound samples, the ISS salmonella typhimurium had altered expression of 167 genes.

Tests on lab mice (pretend they volunteered, alright?) showed that even this short sojourn in microgravity had rendered the microbe three times more deadly. A change in the expression of an important regulator protein, Hfq, is now being linked with the increased deadliness of the sample. ®

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