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Bacteria in space!


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Where humans travel, bacteria will follow. If people are in space for any amount of time, bacteria are sure to thrive there so it’s good to know that there are already researchers looking at how the environment within spaceships affects bacterial populations. Work done on planktonic colonies of bacteria has shown that they can become more virulent and grow faster once they leave earth, but more interestingly there are also changes to bacterial biofilms seen during space flight.

Biofilms are large bacterial colonies that can form on surfaces. They are particularly problematic in hospitals as the bacteria in the bottom of the biofilm are often protected from antibiotics. Biofilms are formed when free-swimming planktonic bacteria clump together, settle down, and coat themselves in slime.

The stages of biofilm development, Each stage of development in the diagram is paired with a photomicrograph of a developing Pseudomonas aeruginosa biofilm. Image from reference 1.

Researchers on the Space Shuttle Atlantis cultured biofilms of the bacteria P. aeruginosa during spaceflight and characterised their properties. They found that the space grown bacteria produced bigger and thicker biomass structures, with more live cells involved. They also found that the structure of the biofilm differed. On earth biofilms form in either mushroom shapes (as shown above) or flat layers. In space they appear to form a series of upright columns with a canopy over the top.

The image below shows three slices through the biofilm on earth (on the left) and in space (on the right). The bacteria are all glowing green. The space bacteria are scattered widely in columns in the bottom slice, and form a dense canopy in the middle and top ones. On earth, each slicecontains around the same amount of bacteria. The biofilm in space is also taller.

Biofilm formation in space. Image from reference 2.

The formation of these column and canopy shapes depends on the motility of the bacteria. When they are able to freely move about (propelled by tentacle-like flagella) the columns form. When bacterial motility is prevented by removing the flagella the columns don’t form and instead the biofilm is made up of sticky layers as it is with non-motile bacteria on earth. The researchers propose that the column and canopy structure is formed by the elongation of the top of the mushrooms in reduced gravity to form a single flattened layer rather than disconnected caps. They also suggest that oxygen levels may play a part in determining the biofilm shape.

The behaviour of biofilms in space is important as plenty of biofilms have been found in spaceships where they cause problems with corrosion and blockage. Astronauts also have lowered immune systems in space, which makes the presence of any bacteria more dangerous. It’s fascinating to see how the biofilm formation adapts to such an alien environment, but I’m sure research is also focussing on how to remove the biofilms completely.

Reference 1: Monroe D (2007) Looking for Chinks in the Armor of Bacterial Biofilms. PLoS Biol 5(11): e307. doi:10.1371/journal.pbio.0050307

Reference 2: Kim W, Tengra FK, Young Z, Shong J, Marchand N, et al. (2013) Spaceflight Promotes Biofilm Formation by Pseudomonas aeruginosa. PLoS ONE 8(4): e62437. doi:10.1371/journal.pone.0062437

Featured image: Earth rise as seen from the lunar surface. From the NASA Marshall Space Flight Center Collection

S.E. Gould About the Author: A biochemist with a love of microbiology, the Lab Rat enjoys exploring, reading about and writing about bacteria. Having finally managed to tear herself away from university, she now works for a small company in Cambridge where she turns data into manageable words and awesome graphs. Follow on Twitter @labratting.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. David Cummings 11:26 am 02/17/2014

    What would happen to biofilms on the interior surfaces of the ISS if humans vacated the place for a month or two, turned off the internal air supply and open the interior up to the vacuum of space?

    When they returned, closed up the station and repressurized, would the biofilms all be sterilized?

    Not saying this is practical, just wondering what the effect would be.

    Thanks, and an interesting post.

    Link to this
  2. 2. S.E. Gould in reply to S.E. Gould 6:03 pm 02/17/2014

    Thanks for the comment! That’s a really interesting question. In the vacuum of space the bacteria would face freezing temperatures, complete lack of oxygen, and no pressure. Pseudomonas needs oxygen, however the bacteria at the base of the biofilm often do not. The freezing temperatures would preserve but likely not kill the bacteria, particularly those protected by the biofilm. As for the pressure and othrr factors such as cosmic radiation and UV light, they might manage to kill off the pseudomonas but there are extremophile bacteria that can survive even these conditions. Bacterial spores would probably survive as well. Overall I’d say that space probably doesn’t count as a sterilising environment!

    Link to this
  3. 3. themadstone 6:15 pm 02/25/2014

    there is a profound implication here- that microbes are capable of adapting to non-terrestrial environments such as zero g through altered behavioral patterns. regular microbial monitoring for pathogens will certainly have to be taken into consideration for any future long-term, manned space flight.

    ps- thought you might find this interesting :)

    http://lonelyspore.com/2013/11/21/could-earth-asteroids-be-seeing-our-solar-system-with-life/

    Link to this
  4. 4. MolecularScribe 10:20 am 03/2/2014

    I’m just wondering, do the bacterial films differ on earth and on space because the different environments favour different types of film arrangments? Perhaps anaerobic bacteria are more likely to dominate the films in space rather than on earth because there is less oxygen available in space? Did the researchers compare films comprising the same species of bacteria on earth and in space?

    Link to this
  5. 5. S.E. Gould in reply to S.E. Gould 4:16 am 03/6/2014

    @MolecularScribe: the same species were compared in the paper, and they also did some interesting work looking at the effect of different levels of oxygen to see whether that was a major contributing factor rather than the change in gravity. There’s a great diagram in the paper showing the result of combined changes in bacterial flow, motility and gravity and what kind of biofilm is produced. It was just a little too involved for the blog!

    Link to this

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