2017 has certainly seen some leaps in the technology and resources available to a handful of organisations that may be most likely to deliver more extensive space travel to more people. This has included a steady increase in the theoretical, experimental and practical research that will underpin how humans and other lifeforms will respond to space flight over longer periods. This includes all normal aspects of human life, including what happens to the bacteria the average person plays host to on an everyday basis.
How would space missions affect bacteria?
All humans are hosts to billions of micro-organisms, with these falling into three basic categories. The first of these consists of pathogens that make you sick. Secondly, humans also host potentially pathogenic bacteria that live on your skin, or on the surfaces of your organs, most often in your intestines. These bacteria aren’t harmful unless their populations become excessive or until they get into an open wound. The third category includes so-called ‘friendly’ bacteria that help your digestive system work, or protect itself from potential or actual bacteria. Little is known about what would happen to the proportions of these bacterial categories if their host was to undertake a space mission. Doing so would entail a drastic change of lifestyle in an environment few humans have had to encounter thus far.
Some research has indicated that bacteria can survive just fine in space, while other studies have shown that some bacterial species won’t make it in exploratory spacecraft. Some scientists conclude that the bacterial contamination of the surfaces within a crewed spaceship might increase their risk of degradation as bacteria establish colonies on, and ‘digest’ high-tech polymers. Additionally, some bacteria also play a role in the formation of rust, including Clostridium tetani, which may cause a neurological disorder in the event of an injury involving corroded metal on which it is present. Clostridium tetani could also potentially damage metallic fittings.
Certain conditions, including microgravity, may impact negatively on the human immune system, thus affecting a crew member’s ability to fight off infections whilst travelling in space. In addition, living in close quarters with other people over prolonged periods may increase the risk of infection with some bacteria. This is known as community- or institution-acquired illness, and is a factor in the rise of some species such as MRSA, commonly acquired during a stay in hospital. As such, there may be a chance that contaminations with pathogenic or potentially pathogenic bacteria may be harder to get rid of in space, particularly in the event that ‘friendly’ bacteria may not respond as well to the completely artificial environments in question. Therefore, a group of researchers working across a number of institutions in Austria and Germany designed an experiment which could illustrate if bacteria would spread under space-flight conditions, and if so, what bacterial types would flourish and propagate.
The conditions the researchers chose were that of six people who volunteered to live in a mock-spacecraft over 520 days. These variables were chosen as they are likely to match with those of a short-term mission to Mars. While living as they would aboard a real spacecraft, the volunteers routinely collected microbiological samples that would indicate whether bacteria were surviving in the experimental conditions or not. The volunteers took 360 samples from various surfaces in the ‘spaceship’ and also from the air in the vessel. They did this 18 times over the duration of the ‘space flight’. The analysis of these samples found that bacteria of potentially pathogenic species were most prominent among the ‘community’ of microorganisms that developed over the 520 days.
In addition, bacteria of all types were most dense in areas where the volunteers spent the majority of their time, namely the living quarters. The two most common species were of the Staphylococcus genus, which includes species such as MRSA, or of the Bacillus genus, which includes species implicated in many conditions including some types of food poisoning. They are potentially pathogenic bacteria; meaning that they are present on body surfaces all the time, and are only harmful if they get into an open wound, are allowed to propagate themselves in the absence of natural mechanisms of bacterial resistance, or acquire dangerous mutations that allow them to overcome strategies such as antibiotic treatments. On the other hand, the bacterial communities measured over the course of the experiment were kept under the levels typically allowed on the International Space Station (ISS). This was due to routine cleaning and hygiene protocols that are likely to be employed on a real live space flight.
This experiment indicates that areas within a spacecraft designed for travel between Earth and destinations like Mars are capable of sustaining some level of bacterial life, although it may be controlled through basic hygiene, just as on Earth. On the other hand, most of the bacteria cultured from the experimental crew-module came from one main source: dead human skin. This may explain why Staphylococci were some of the most abundant species. This experiment did not document the levels of ‘friendly’ human bacteria, which may help resist potential spaceship-borne illnesses. Therefore, based on the research done to date, probiotic drinks manufacturers of the future may find markets in intergalactic communities.
This experiment also found that there was an appreciable level of diversity (or many different types of species) within the bacterial ‘communities’ on board the experimental vessel. This is a desirable state of affairs, as bacterial diversity may keep pathogenic or potentially pathogenic species under control. However, this diversity dropped off over time, and the potential pathogens achieved an increasing majority. The essential messages of this study appear to be that the skin shed by crew members on a space mission needs to be disposed of with care, and that the same missions may be less bearable for some potentially beneficial bacterial species.
Top image: An interplanetary spacecraft may not be the ideal habitat for bacteria. Source: NASA
Schwendner P, Mahnert A, Koskinen K, Moissl-Eichinger C, Barczyk S, Wirth R, et al. Preparing for the crewed Mars journey: microbiota dynamics in the confined Mars500 habitat during simulated Mars flight and landing. Microbiome. 2017. 5:(1). pp.129.
Masterson A. Microbes may not make it to Mars. Cosmos Magazine. 2017. Available at: https://cosmosmagazine.com/space/microbes-may-not-make-it-to-mars