How do astronauts deal with space sickness

What diseases are lurking in space?

Weightlessness can weaken the immune system and make people more susceptible to disease. At the same time, it seems to influence the stress reactions of the microbes, making them more virulent and robust. Dozens of studies, conducted both in space and in simulated weightlessness on Earth, suggest that space flight alters the response of some bacteria to their environment.

"It was quite a surprise to see differences in the virulence of the microorganisms during spaceflight," says Nickerson. Her laboratory demonstrated that the salmonella strain Typhimurium, which triggers an unpleasant gastrointestinal inflammation in people, becomes even more infectious after a while in weightlessness.

In 2006 they sent some salmonella bacteria into space on board the space shuttle Atlantis. While Nickerson and her team grew salmonella cultures on Earth, the astronauts did the same in space. When the shuttle returned, Nickerson infected laboratory mice with the salmonella that were bred on Earth and a control group with the salmonella from Earth orbit.

The result was clear: the space flight had the virulence of Salmonella Typhimurium increased. The bacteria now killed the mice much faster and at lower doses. Nickerson points out, however, that the effect was temporary.

“That was a short-term experiment,” she says. “It wasn't a permanent and hereditary change. The bacteria simply adapted to their environment. If you take them out of this environment, the way they adapt changes again. [...] That is simply in the nature of bacteria. This is exactly what they do when they infect us elsewhere. "

Further research revealed that weightlessness mimics an environmental signal that normally signals to cells that it is time to start infection - namely, a reduction in the force with which fluids flow across the cell surface. On Earth, this relative dormant state could occur somewhere in a sheltered corner of the intestines or lungs. Basically, it is ubiquitous in space.

"Nobody has proven that before," says Nickerson. "Nobody thought that a physical force could change the virulence or pathogenicity of an organism."

Where germs thrive

So far, however, Salmonella are not the only microbes in which an increased virulence has been detected in living animals as a result of space flight. Numerous other studies suggest that weightlessness can affect microbial growth, size, metabolism, and resistance to antimicrobials, among other things.

The experiments tested known microbes such as E. coliYersinia pestis (the plague bacterium),Streptococcus mutansStaphylococcus aureus, Bacillus subtilis andCandida albicans, the fungus that causes yeast infections. Some of the microbes became more virulent in weightlessness, while others showed the opposite reaction or no reaction at all.

“Various experiments over the past 50 years have revealed unique microbial reactions when microorganisms are cultivated during space flight. These include changes in growth behavior, resistance to antimicrobials and the formation of biofilms, ”reports NASA scientist Mark Ott.

Biofilms in particular can be a major problem for human health and environmental systems. These accumulations of microbes grow on surfaces and form complex layer structures there, which can contribute to the resistance of the germs. Therefore, they are extremely difficult to treat, especially in the human body, and they also settle on important structures of space stations.

"The majority of bacteria in nature exist in surface-associated microbial communities," wrote Cynthia Collins of the Rensselaer Polytechnic Institute and her colleagues in a recent study. "Abundant biofilms were found on the Russian Mir space station, which accelerated corrosion and clogged the water treatment system."

In 2011, Collins and her colleagues sent Pseudomonas aeruginosa aboard the space shuttle Atlantis into space - the microbe that was responsible for the ailments of astronaut Fred Haise. In space grew Pseudomonas then quickly came to a biofilm that was larger and thicker than its counterpart on the surface of the earth. In addition, the biofilm had a structure that, according to the scientists, has not yet been observed on Earth.