The experiment was conducted during the nearly twelve-day STS-115 mission of the space shuttle Atlantis in September 2006. Nickerson and her associates sent Salmonella typhimurium bacteria into space and then compared it with identical bacteria that remained on Earth.

Her results found that the bacteria sent to space inside a growth chamber were about three times more deadly than the earthbound ones that were kept inside an orbital simulator at the Kennedy Space Center in Florida. In fact, Nickeson states that 167 of the genes within the S. typhimurium changed—turning the bacteria more dangerous to humans.

Nickerson says this information could be used to "design targeted strategies and countermeasures to mitigate infectious disease risks to the crew during future missions". [New Scientist article, Subscription required.]

Salmonella typhimurium bacteria are a main cause of food poisoning and typhoid fever in humans. It can lead to human gastroenteritis, which is also known as salmonellosis, which causes fever, diarrhea, and abdominal cramps one-half to three days after being infected by the bacteria. Salmonellosis is usually transmitted through the feces of humans and animals. It causes millions of cases of sickness each year throughout the world, and many deaths occur annually due to the infection.

Nickerson comments, "Until now, we didn't know how real spaceflight would affect these bacteria."

The findings brings up the issue that space travelers have a tendency to get weaker bones and muscles when in space and their immune system is not as efficient in fighting off germs. With this information that germs are more dangerous in space, it is very important that NASA and other space agencies learn more about the science behind bacteria in space. Such information will indirectly help fight bacteria-based diseases and related infections on Earth.

Currently, Nickerson and other scientists think that bacteria become more dangerous depending, in part, on how fluids move around the surface of the cells of bacteria. Such movement, which is called fluid shear, tells the cells whether or not to turn on various genes to assure they survive during times of troubles (such as being subjected to an extreme environment as found in space). The cells turn on certain genes with a genetic switch called ‘Hfq’ when the fluid shear is low; that is, when there is low movement of fluid around the cell. (In all, the genetic regulator Hfq controls about 160 genes.)

When the genes are activated, they turn the cells more dangerous—at least for humans—but more safe for them. This action is important, both in space and on Earth. Movement of fluids, fluid shear, around such cells is low in space, but it is also low in the body’s intestines. The intestines are ideal locations for bacteria to multiple because of its temperature, plentiful amounts of nutrients and low fluid shear; thus, making them more likely to cause infections and diseases.

Additional missions to study these and similar bacteria in space-based and ground-based experiments are planned for the future.


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