Final frontier: Astronauts’ microbiomes go under the microscope to advance deep space missions

23 Feb 2024 --- The well-being of astronauts is paramount to the stability of space exploration. Space researcher and professor Dr. Lembit Sihver is pioneering new research into their microbiomes to see how exposure to extreme conditions such as microgravity and ionizing radiation influences the balance of bacteria.

“While on a space mission, astronauts do not get the same replenishment of microbes that they get on Earth. The traditional view of health microbiology is that microbes make you sick and should be removed from the spacecraft environment whenever possible,” Sihver, founder and chief technology officer of the Cosmic Shielding Corporation, tells Nutrition Insight.

“Astronauts’ food is specially designed to last for long periods of time and has almost no microbial content. To minimize the risk of infections, the air that astronauts breathe on space missions is heavily filtered, and everything shipped to the ISS (International Space Station) is monitored to remove as many microorganisms as possible.”

Research on the human microbiome and its adaptation to space has become a crucial field of study for the success of long-term space missions, specifically for trips to Mars. The microorganisms that live in the microbiome influence digestion, immunity and the regulation of various physiological processes, which can be disrupted in space and lead to deteriorated health in astronauts. 

Scientists have investigated the adaptation of microorganisms unintentionally introduced to the extreme environment of the ISS over its 20-plus years of service. The current study revealed that these microorganisms have undergone adaptation to life in space. The research team observed various features in these microorganisms that are not typically found in their Earth-bound counterparts. These features enable them to thrive and adapt to the challenging conditions of space. 

“The findings of the study suggest a convergent adaptation among the diverse microorganisms isolated from the ISS. The presence of mechanosensitive channel proteins, increased DNA repair activity, as well as metallopeptidases and novel S-layer oxidoreductases indicate a potential complementarity among these microorganisms within the context of the ISS microbiome,” Sihver explains. 

Astro microbiological preparedness
Research into microorganisms in outer space — astro microbiology — seeks to analyze and understand the effects of microbial persistence and succession on closed systems, such as spacecraft and habitats. It goes further to develop technologies such as space agriculture and the extraction of microbial secondary metabolites for medicine, flavoring and nutritional drugs. Sihver’s latest paper on the topic was published in Frontiers in Microbiology.

“While keeping an extremely clean spaceship environment has been an effective preventive measure for protecting astronauts from infections caused by many dangerous pathogens, the lack of microbial intake for long periods of time has a detrimental effect on the diversity of the crew microbiota and, therefore, on astronaut health, to a sufficient extent that it may not be a viable strategy for long-term space missions,” Sihver underscores.

For example, astronauts who spend 6–12 months aboard the ISS have experienced changes in the gut microbiota and different physiological changes. “The gut microbiome plays a crucial role in maintaining the overall health of the host, including astronauts during space travel. It affects the general immune system, metabolism, neurological strength, as well as the muscles, bones, cardio and the ocular/retinal immune system.”Further research about adaptive responses to pathogens can help further the understanding of the human gut microbiome in space (Credit: National Institute of Allergy and Infectious Diseases). 

“Therefore, it is essential to regulate the gut microbiome for the success of long-term space missions. One way to achieve this is potentially mediated by optimizing astronauts’ diets to include adequate amounts of dietary fiber, prebiotics, bioactive compounds and probiotics.” 

“Alternatively, the transplantation of the fecal microbiota of the crew members into probiotic capsules before the onset of the spatial journey allows astronauts to diversify their microbiome with their own set of microorganisms,” Sihver posits.

Integrating astro microbiological preparedness into space mission planning and execution is a crucial safety protocol to ensure the overall health and well-being of astronauts and the subsequent success of the trips. It can also help the rehabilitation process for astronauts when they return to Earth. 

The unusual conditions of space and dietary changes are likely to disrupt the balance of the human microbiome. Scientists like Sihver are currently developing strategies to mitigate the adverse effects of microbiome alteration during space travel.

Risk reduction from space pathogens
The likelihood of infection by pathogens occurs when there are changes in the composition of intestinal flora — possibly due to environmental or genetic changes — and encourage harmful organisms to spread, induce disease and contribute to inflammatory disorders. 

“Space radiation and microgravity are the key stressors. The microorganisms in the microbiome are exposed to radiation, which can induce resistance to antibiotics, UV, heat, desiccation and other potentially fatal factors. They are also exposed to microgravity. These factors can affect the interaction between the microbiome and immune system, which can lead to different infections,” says Sihver.

Studying the microbiome helps researchers understand the impact of space on the human immune system. Microorganisms of the microbiome produce essential vitamins that regulate and modulate the immune system. The temperature variations, oxygen levels and diffusion limitations of the space environment provide the opportunity to optimize the production of metabolites by genetically modified microorganisms.

Furthering astro microbiology can lead to the discovery of new microorganisms with unique properties and abilities that could be used to develop new drugs, antimicrobial agents or advanced biotechnologies.Astro microbiological preparedness is a growing area of research to advance space travel (Credit: Adam Miller).

A potential danger to the microbiome of astronauts in space is the spread of pathogenic microorganisms in the enclosed environment of a spacecraft. Confinement and recycled air systems can promote the spread of pathogenic microorganisms. The prolonged exposure to microgravity can suppress the astronauts’ immune system. Previous research shows that a compromised immune system hampers their ability to counter harmful microorganisms effectively.

Concerns about antibiotic resistance
The scientific community is concerned about antibiotic-resistant genes in the gut microbiota of astronauts, supported by plasmids, which can undermine the effectiveness of antibiotics. The presence of a pathogen in a spacecraft can jeopardize the health of all the astronauts on board, especially those with compromised immune systems, particularly during extended missions.

“We will especially look into how radiation might induce resistance to antibiotics, UV, heat, desiccation and other potentially fatal factors. Since this can have serious implications for the people and the mission,” Sihver outlines.

The spread of antibiotic-resistant genes can undermine medical interventions during a mission, further exacerbating the circumstances of a mission. 

Further to this, the spread of antibiotic resistance genes could undermine medical interventions, exacerbating health challenges during the mission. Addressing these concerns is crucial for mission success and astronaut well-being.

“This study highlights the remarkable ability of microorganisms to adapt and survive in the unique and demanding environment of space. They can also undergo adaptive response to become more resistant to the hard radiation environment in space. Further research in this area is crucial for understanding the implications of microbial adaptation in space travel and ensuring the safety and success of future deep space missions,” Sihver concludes.

By Inga de Jong