We are getting closer and closer to sending astronauts to Mars and consolidating space tourism flights. However, there are still many variables that must be taken into account for these trips to be truly safe. One of the factors, and a very important one, has to do with microorganisms. Every human being is the carrier of thousands of viruses, bacteria and fungi: they are our microbiome, and they accompany us wherever we go: also into space. But in space conditions change, and it is necessary to know what happens with microbes, especially since we are talking about organisms with a very high capacity to undergo mutations. Not surprisingly, bacteria have colonized practically every environment on our planet, even the most inhospitable. In addition, we must bear in mind that, here on Earth, we can open the windows and ventilate our houses, go out for a walk, air out … in space travel, people find themselves in hermetic capsules in which, obviously, the air does not circulate.
At the end of 2018, a study carried out with several strains of the Enterobacter bacteria found on the International Space Station (ISS) warned that, although they have not been pathogenic so far, there is a 79% probability that they potentially cause disease. Now, a new work published in the journal mSystems describes a new analysis carried out with bacteria from the ISS, in this case with Staphylococcus aureus and Bacillus cereus . The results reveal that, despite the extreme conditions, it does not appear that bacteria on the ISS are mutating to become dangerous or antibiotic resistant ‘superbugs’.
They mutate to survive
The Northwestern University researchers found that while the strains studied contained different genetic material than their Earth counterparts, these genes did not make the bacteria more harmful to human health. According to the authors of the work, bacteria are simply responding, and perhaps evolving, to survive as best they can in a very stressful environment.
To carry out their work, the scientists used a public database provided by the US National Center for Biotechnology Information and which contains the genomic analyzes of many of the bacteria isolated on the ISS. The species chosen are from different environments: S. aureus lives on the skin and one of its strains, called MRSA ( methicillin- resistant Staphylococcus aureus), is difficult to treat due to its resistance to antibiotics. B. cereus , by contrast, is soil-dwelling and its activity has fewer implications for human health.
“The bacteria that live on the skin are happy there,” explains Erica Hartmann, leader of the study. “The skin is warm and contains oils and organic chemicals that they like a lot. When you eliminate the bacteria from your skin, they suddenly find themselves living in a very different environment: the surface of a building is cold and sterile, it is a very stressful environment ”.
To take over this new life, bacteria have great allies: their genes. It seems that under the new conditions genes can be activated that confer some kind of adaptive advantage or that can even mutate. The goal: to eat, grow and function in an environment very hostile to them. “Based on genomic analysis, we can say that, apparently, bacteria are adapting to survive, not to cause disease,” explains Ryan Blaustein, another of the authors. “We have not found anything that indicates a greater resistance to antibiotics or a special virulence in the bacteria analyzed by the ISS”.
Although this is good news, the researchers are cautious. “Astronauts are people in excellent health. But if we are talking about generalizing space flights and including tourists who do not necessarily meet the criteria for the physical condition of astronauts, we do not know what can happen. What happens if we put someone with an infection in a closed bubble in space? It’s like when someone coughs on a plane and everyone gets sick, the most likely thing is that the infection will spread ”, Hartmann concluded.
Reference: Blaustein et al. 2019. Pangenomic Approach To Understanding Microbial Adaptations within a Model Built Environment, the International Space Station, Relative to Human Hosts and Soil. mSystems, 2019; 4 (1) DOI: 10.1128 / mSystems.00281-18
Photo: NASA / Roscosmos
