Many of us have dreamed of flying at zero gravity unhindered, in the darkness of space – floating through a cool vacuum with stars shining all about and the blue dot of planet Earth below. But, despite how awesome the daydreams are, the reality of flying through space would be pretty uncomfortable. As the blog IFLS so eloquently put it, if you were to fly unprotected in space "you’d swell up, burn, mutate, pass out and your lungs might explode".
That's all very well for humans – but as we have touched on before, microbes are a lot stronger than us. And what's more, the incredible water bears (also known as tardigrades) are not even the only ones that can likely survive in space! Some bacteria can probably tag along with the tardigrades just fine.
Like different species of animals, different species of bacteria are specialized to different environments. Just like you won't find scorpions living at the bottom of the ocean, you are unlikely to find Vibrio fischeri living on wild lilacs. However, one group of bacteria (for any real science nerds reading, that would be several species of bacteria in the Firmicute phylum) has a particularly impressive ability to withstand challenges in a huge variety of habitats. Some of these bacteria, such as Bacillus species, are able to survive for thousands or even millions of years in weird environments like salt crystals. How do they pull off this miraculous feat? Endospores!
Endospores are kind of like cryogenic chambers for bacteria. You can picture the scene in Austin Powers, the International Man of Mystery in which our favourite spy emerges (more or less) as good as new after being frozen for decades. Endospore-forming bacteria are able to do more or less the same, but the process is a little more complicated than just cooling themselves down, like Mr. Austin Danger Powers did.
When bacteria form endospores, they make a series of changes to their "bodies" that allows them to go into a sort of hibernating state. This is usually in response to some sort of negative change in the environment of bacterium – like being encased in salt or shot out into space, where there isn't enough water for the bacterium to survive as it already is. The ultimate goal of endospore formation is to protect the DNA of the bacteria, so that when it's living conditions improve, the bacteria can emerge (more or less) as good as new.
There are three main things that bacteria will do to create its personalized preservation chamber. First, the bacterium will build a biological wall around it's DNA, to protect it from damage during its "hibernation". Secondly, the bacterium will produce a lot of a special acid that seems to help endospores stay dormant. Finally, the bacterium will dehydrate itself. It's better for the bacterium to sort of plan its own dehydration than to be taken by surprise and dehydrated by a lack of water in its environment later on! When the bacterium is done, all that remains is the spore, and the rest of the original cell will dye off.
Bacterial endospores can cause a lot of problems, because they are so tough. They resist boiling, dehydration, radiation, and even antibiotics and disinfectants. This is pretty annoying in the setting of a hospital. But it's also pretty interesting in the setting of outer space.
A variety of different scientists, including some affiliated with the European Space Agency and NASA, have shown that bacterial spores are decidedly superhuman. After two weeks in space, most of the bacterial endospores these astromicrobiologists tested died because of very high UV radiation. However, with just a little added protection in the form of some rock, clay, or meteorite powder, almost all of the spores were able to survive a trip into space!
Why are people studying this, and why is this an important finding? There are two main reasons. First of all, now that we humans are sending off space ships to other planets, it's important to know what bacteria might be stowing a way and possibly contaminating other celestial bodies. For instance, we don't want any stowaway bacteria tricking us into believing that they were on Mars before us – we want to know for sure if Martian bacteria are really Martian.
Secondly, finding out more about how microbes can survive in space teaches us about how life might have spread through space before us humans entered the picture. If endospores can survive in space with the help of meteorites, that means that it's conceivable that meteorites could have brought bacteria to Earth. As of yet, we don't know for sure – but there's definitely a bright future ahead for aspiring astromicrobiologists to investigate more into the history of life in our Universe!
Until next time, appreciate the endospores!
~ Alex
P.S. Special thanks to Dr. Janet Kluftinger and Dr. Richard Plunkett for this post - it's largely composed from lecture notes from their undergraduate classes!