Will gut microbes determine whether humans can survive in space?

Mondo Health Updated on 2024-02-22

Editor's note:This article was published yesterday (Feb. 21) in Universe Today by Matt Williams. Compiler Cao Zhi, the content is for reference.

For more than a century, humans have dreamed of one day (being able to explore space as a species). In recent decades, with the rise of the commercial space industry (Newspace) and plans to establish habitats in low-Earth orbit (LEO), on the surface of the moon and even on Mars, interest in space exploration has reached a new peak, and the dream seems to be within reach. Judging by the current situation, it is clear that space exploration will no longer be the "exclusive mission" of astronauts and official space agencies.

But before the Great Migration can begin, there are many issues that need to be addressed. For example, what will be the impact of long-term exposure to microgravity and space radiation on human health? This in turn includes in-depth research into the effects of muscle and bone density loss, and how the (long and relatively lonely) time spent in space will affect human organs such as cardiovascular and mental health. In a recent study, an international team of scientists looked at an area that had often been overlooked in previous related research: the microbiome (changes in space) in the human body. In short, what impact will "time" in space have on the gut microbiome, which is critical to our health?

The team consisted of biomedical researchers from the Research Centre for Protection against Ionizing and Non-Ionizing Radiation (INIRPRCR) of the Shiraz University of Medical Sciences (SUMS) in Iran, the International University of Lebanon, the International University of Beirut, the University of Glasgow (MVLS) in the United Kingdom, with the participation of the Center for Applied Mathematics and Bioinformatics (CAMB) of the Gulf University in Kuwait, the Institute of Nuclear Physics (NPI) of the Czech Academy of Sciences (CAS), and the Institute of Atomic Studies of the Vienna University of Technology. The team's work was recently published in Frontiers in Microbiology.

The microbiome is a collection of all microorganisms that live on and in our bodies, including bacteria, fungi, viruses and their respective genes. These microorganisms are key to our bodies and their interactions with the surrounding environment, as they can influence the body's response to invading viruses and their original substances. In particular, some microorganisms alter the invading virus and enhance the latter's destructive power, while others act as a "buffer" against the invading foreign virus to mitigate the effects of the toxin. As they noted in their study, astronauts' microbiota on and off the surface of their bodies will be "under pressure" from microgravity and space radiation, including cosmic ray GCR.

Cosmic rays are a type of high-energy radiation consisting mainly of protons and nuclei of deprived electrons that have been accelerated to near the speed of light. When these rays are generated by those elements heavier than hydrogen or helium, their high-energy nuclear components are known as hze ions – a particularly dangerous substance. Secondary particle rain occurs when these particles affect our atmosphere or spacecraft, as well as the protective shields on the International Space Station (ISS).

While Earth's protective magnetosphere and atmosphere prevent most of these particles from reaching the surface, astronauts in space are able to access them regularly. As the researchers noted in their report, previous studies have shown that this exposure (exposure) may enhance astronauts' ability to adapt to radiation, a process known as "radio adaptation." However, they also point out that the degree of radio adaptation varies from astronaut to astronaut, and that some astronauts have (and may have) experienced "adverse biological influences" (in this case, a particular virus) before embarking on a mission to explore deep space.

Therefore, the researchers recommend further research to determine the risks associated with the space environment, which is full of protons and astronauts are exposed to other protons before encountering HZE particles. Third, NASA's multi-mission operational model suggests that astronauts can make "dose adjustment" their first mission. However, the team noted that current research suggests that multiple space flights do not necessarily elevate the likelihood of genetic abnormalities (to continue to improve fitness) as expected, which could mean that the body may have a natural mechanism to defend against excessive "radio adaptation."

In terms of recommendations, the team believes that the ISS is an ideal environment to test the human microbiome's response to space radiation and microgravity. They also address many previously unexplored issues in the field, including the long-term effects of radiation on the microbiome and environmental bacteria:

The International Space Station (ISS) is a self-contained, controlled system that can be used to study the interactions between the human microbiome (when in space) and the microbiota of its habitat. According to the researchers, the ISS is a hermetically sealed, closed system, but it houses many microbial ......In this case, NASA scientists failed to take into account that the "adaptation" may not be limited to astronauts and bacteria in astronauts; Nor does it take into account that bacteria on the space station can trigger resistance not only to the intense DNA damage caused by HZES (the drugs taken at the time), but also to "other threats to bacterial activity" (such as antibiotics).

The increase in antibiotic resistance can endanger the lives of astronauts, who are often at risk of injury and infection during long-term missions. In addition, the researchers highlighted in the report that space travel and prolonged exposure to microgravity weaken the body's immune system and reduce astronauts' natural resistance to microbes, especially those that are highly resistant to radiation, heat, ultraviolet rays and dryness, which tend to be better suited to survive in space. As the researchers conclude:

Compared to astronauts, the microbiome is more adaptable to the harsh environment of space because they can evolve and adapt faster than humans by 'quickly acquiring microbial genes'. The 'generation' time of microbes is much shorter, allowing them to produce more offspring, each with a unique genetic mutation that can help them survive in the space environment."

Therefore, the research team stressed that additional studies are needed to assess the degree of adaptation of microorganisms before carrying out the mission. This is essential for identifying potential risks and developing mitigation strategies, innovations** and interventions. They also recommend that astronauts undergo regular cytogenetic tests to measure their "adaptive responses" and that only those astronauts who exhibit a high adaptive response to lower doses of radiation should be selected for those missions that are exposed to higher doses of radiation.

They also acknowledge that there are some challenges in studying the astronaut microbiome in space. These include the difficulty of conducting experiments in microgravity, as the specific environment can affect the growth and behavior of microorganisms (whose data can be captured at a frequency different from that of Earth), making it more challenging to obtain accurate and reliable data, and the potential danger of pathogen transmission in closed environments with recirculating air systems. However, this research needs to be carried out before manned deep space exploration can be realized, as it requires the identification of potential pathogens and the development of strategies to prevent their spread during the mission.

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