Bacteria that have been launched into space become deadlier than their earthbound counterparts, according to a new study. The finding may provide fresh insights on how to combat bugs right here on terra firma.
Space agencies around the world are beginning to plan missions to the moon and eventually to Mars and beyond. During those missions, astronauts will be exposed not only to external dangers such as solar radiation and micrometeorites but also to internal hazards such as bacterial infection. For that reason, researchers want to learn more about how bacteria behave in space flight. For example, does weightlessness affect microscopic organisms in the same way it does humans and other living creatures?
To find out, researchers sent samples of Salmonella typhimurium, a common infectious bacterium used in lab studies, aboard the space shuttle Atlantis for 12 days in September 2006. They performed detailed genetic and protein-expression analyses on the Salmonella samples after the specimens returned to Earth. Reporting online this week in Proceedings of the National Academy of Sciences, the team found that after a 2-week stint in space the microbes were three times more able to kill infected mice than were control samples that remained on the ground. The flight also changed the expression of 167 of the bacterium's genes, including one for a protein called Hfq, which could be the key molecule responsible for the increased virulence.
Microbiologist and lead investigator Cheryl Nickerson of Arizona State University in Tempe says the Salmonella's increased virulence is easily treated by antibiotics, but what's important about the study is that it revealed the cause of the change: The low gravity led to a condition called low fluid shear, in which the bacterium's liquid environment reaches a gentle but not absolutely still state, similar to what the bug encounters inside the body during infection. When the scientists duplicated low fluid shear in lab experiments on the ground, the Salmonella samples acted in many of the same ways they did aboard Atlantis. This insight should give researchers new ways to design therapies that could disrupt the Hfq protein and perhaps stop infectious agents like Salmonella dead in their tracks, says Nickerson. "We've [now] got a tremendous amount of data" on how low fluid shear affects bacterial responses, she says.
Space bioscientist Lynn Harper of NASA's Ames Research Center in Moffett Field, California, agrees that the findings hold promise. The study provides solid evidence for medically important phenomena that were only hinted at in prior research, she says: "There is increasing evidence that space can provide important new tools for learning to fight certain diseases."