Sorting out how microbes survive on supposedly sterilized spacecraft
As much as humans want to discover life on other planets, we also want to make sure we didn’t accidentally send it there. Humans have a bad track record with introducing invasive species on to environments on our own planet, and we would really like to avoid doing so as we explore other planets. Allowing for crewed missions to Mars at some point in the future, a lot of effort goes into decontaminating any spacecraft that will be sent to potential ecosystems, like the Curiosity rover on Mars. Since there’s a good chance that some bacteria may be able to survive a trip through space, these spacecraft are assembled so called “clean rooms,” minimizing contact with the multitude of microbes that live in every other environment on Earth. Bunny suits and sterilization procedures have been fairly successful, but it seems that life has found an opportunity in these otherwise unoccupied environments. Not only have some microbes specialized to live in clean rooms around the world, but they’ve done so by evolving to eat our cleaning products.
Scientists have found traces of a variety of microbes on our spacecraft, including bacteria, fungi and single-celled archaea. To investigate the ecology of these unwanted microbiomes, students from Cal Poly Pomona focused on Acinetobacter, the most common genus of would-be astro-bacteria. Samples were collected from the rooms where the Odyssey and Phoenix spacecrafts were built, then analyzed to see how they could survive in supposedly sterile environments. Even if the bacteria were somehow hearty enough to survive contact with a cleaning agent, it wasn’t clear what these microbes could all be eating in these spaces in order to grow and multiply.
Consuming the cleansers
Normally, a cleaning agent like isopropyl alcohol sterilizes a surface by ripping bacterial cells apart. The lipids in the cell membrane basically dissolve in the presence of alcohol, rupturing the organism entirely. Acinetobacter aren’t necessarily immune to this chemistry, but if they aren’t wiped out completely they do use the alcohol to their advantage. As the alcohol biodegrades, the bacteria actually eat its carbon as their primary source of food. They were also able to take on Kleenol 30, another common cleaning agent. If that wasn’t resilient enough, Acinetobacter turned out to be able to survive a fair amount of oxidative stress. This means that they could possibly handle the higher radiation levels of space, as well as the dry conditions on a planet like Mars.
This doesn’t mean that every spacecraft we build will necessarily lead to a bacterial invasion on other planets. Missions that might involve contact with habitable environments, like the surface of Mars or a wet moon like Enceladus, will simply need to be cleaned more rigorously than before. Knowing how bacteria like Acinetobacter live off of our usual cleaning supplies will spur the development of new strategies, keeping spacecraft clean until the next round of bacterial evolution catches up with us.
Source: Team discover how microbes survive clean rooms and contaminate spacecraft by California State Polytechnic University, Phys.org