Surviving in space is not something that our bodies are designed for and we might assume that the same thing applies to every single organism found here on earth. The thought of an organism being able to survive in space is riveting in itself, not least because of the harsh conditions found in outer space.

However, to our surprise, astronauts have found bacteria on the exterior surface of the International Space Station. This poses several questions, including where these bacteria came from and how it is possible for an organism to survive in space.

Investigations into the matter revealed that the bacteria actually originate on Earth. These could have been carried into space either on the equipment brought along or from the astronauts themselves.

To make things even more interesting, NASA announced that the interior of the International Space Station is also covered with bacteria. The side of the space station facing the Sun reaches 250 degrees F, while the side facing away from the Sun is minus 250 degrees F. Now, add to this the constant bombardment of cosmic radiation and ultraviolet light and you are looking at a very inhospitable setting.

Naturally, we might think anything on the outside of the space station would die very quickly. But these bacteria have proven that it is possible for organisms to survive in space.

NASA conducted studies on the bacteria to find out how they can survive in the harsh conditions in space. The answer lies in the anatomy of certain bacteria, whose unique characteristics make it possible for them to stay in a vacuum without getting destroyed.

For example, the spores of Bacillus pumilus SAFR-032 can withstand UV radiation as well as hydrogen peroxide treatments. This can help the bacteria to survive in harsh conditions. However, the bacteria will eventually die if they cannot find a suitable living space.

Another example is tardigrades, tiny organisms that typically live in water. During a 2014 examination of the ISS, Russian astronauts found tardigrades stuck on the outside of the space station. On further analysis, researchers found that it is possible for these organisms to shield their DNA from X-ray radiation.

NASA confirmed that there are also several different species of bacteria living on-board the ISS with the astronauts. In fact, the conditions inside the ISS favours many of these bacteria. NASA has a catalogue of all the bacteria living on the ISS and they use this information to develop safety precautions for future interplanetary flights.

The microbes found on the ISS come from humans and are similar to those found in gyms, offices, and hospitals on Earth. The ISS is a hermetically sealed closed system and is subjected to radiation, elevated levels of carbon dioxide and the recirculation of air – exactly the type of environment where bacteria tend to thrive.

Bacteria found inside the ISS include Staphylococcus aureus (commonly found on the skin and in the nasal passage) and Enterobacter (associated with the human gastrointestinal tract). Although these organisms can cause diseases on Earth, it’s unclear what effect, if any, they would have on the ISS inhabitants.

The study of these microbes is important because astronauts during spaceflight have altered immunity and do not have access to the sophisticated medical interventions available on Earth. Previously, the only way to identify a particular bacteria or microorganism on the space station is to bring the specimen back to Earth for research. This can cause a severe delay, especially if an astronaut becomes ill.

That all changed in 2016 when NASA astronaut Kate Rubins sequenced microbial DNA on the ISS. She was guided from Earth by NASA microbiologist Sarah Wallace and her team at Johnson Space Center in Houston. The results proved to be accurate and the ability to sequence DNA in space could provide many advantages in the future.

Gravity can affect the way organisms, including bacteria, behave. When researchers analyzed bacteria on the ISS, they found that the bacteria tend to multiply in higher numbers, and are more resilient to antibiotics than when they are on Earth.

There have been several theories as to why these bacteria exhibit physiological changes in space. One of the leading hypotheses is that without gravity, the rate of molecular activity within and outside of the bacterial cell is very limited.

This pushes the bacteria into a type of starvation mode, where they exhibit characteristics that are unique to low gravity environments. However, not every type of bacteria will respond in the same way.

In order to collect more concrete data on bacterial behaviour in space, it will be necessary to perform a wider range of experiments on the space station. As we discussed earlier, NASA and other space agencies around the world have been both intrigued and concerned by the idea of microorganisms thriving in and on the space station.

Currently, these microorganisms are thought to pose no threat to the astronauts living there, or to the structure of the ISS itself, but understanding the growth and variety of these microorganisms is of great importance. There is also the possibility of the microorganism interfering with experiments being run on the ISS.

Space agencies are carrying out active research studies to catalogue the microorganisms present in the space stations and are regularly monitoring their levels.

Humans are no longer the only living things on the ISS.

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