In an extraordinary experiment, some of these microbes were recently sent to the International Space Station (ISS) as part of a study directed by Space Center Houston’s Manager of Science and Research, Phyllis Friello. The research team is currently evaluating how effectively these microbes survived the space conditions.
“Our project focused on reinforcing microorganisms for extreme environments. We envision a wide range of uses, including space missions, medical applications, and agricultural advancements,” states Giovanni Traverso, an associate professor of mechanical engineering at MIT, who is also a gastroenterologist at Brigham and Women’s Hospital and serves as the study’s senior author.
Miguel Jimenez, a former MIT research scientist now an assistant professor of biomedical engineering at Boston University, is the lead author of the research paper published in Nature Materials.
Thriving Under Pressure
Nearly six years ago, with funding from NASA’s Translational Research Institute for Space Health (TRISH), Traverso’s lab began investigating methods to boost the resilience of beneficial bacteria, such as probiotics and microbial therapeutics. Initially, the researchers examined 13 commercially available probiotic products and found that six did not contain as many live bacteria as advertised.
“Our findings suggested a substantial discrepancy between what’s claimed and the reality. This led us to the next question: How can we improve this situation?” Traverso replied.
The team focused on four specific microorganisms: three bacteria—Escherichia coli Nissle 1917 (a probiotic), Ensifer meliloti (a nitrogen-fixing bacterium), Lactobacillus plantarum (used in food fermentation)—and the yeast Saccharomyces boulardii, also a probiotic.
Typically, microbes destined for medical or agricultural use are lyophilized, transforming them into a powdered form. However, turning them into more suitable formats, like tablets, usually involves organic solvents that can endanger bacterial viability. The MIT team aimed to discover additives that would bolster the microbes’ resilience throughout this processing.
“We developed a systematic approach, utilizing materials from the FDA’s ‘generally regarded as safe’ list, combining them with bacteria to identify which ingredients could enhance bacterial stability during lyophilization,” Traverso noted.
Their experiments allowed researchers to mix various microbes with around 100 different ingredients and observe which combinations best sustained their viability when stored at room temperature for 30 days. This process unveiled various ingredients, primarily sugars and peptides, that were particularly effective for each microbial species.
Choosing E. coli Nissle 1917 for further refinement, the researchers discovered that a combination of caffeine or yeast extract with the sugar melibiose could produce an exceptionally stable formulation. This formulation, dubbed formulation D, demonstrated over a 10% survival rate after six months at 37 degrees Celsius, while a commercial version of E. coli Nissle 1917 showed complete inactivity after just 11 days at the same temperature.
Moreover, formulation D withstood much higher levels of ionizing radiation, up to 1,000 grays—contrast this with Earth’s typical exposure of merely 15 micrograys per day and around 200 micrograys per day in space.
Although the researchers are still uncovering the mechanisms behind their formulations, they speculate that the additives may play a role in stabilizing bacterial cell membranes during rehydration processes.
Testing Their Limits
The research team then proved that these microbes could not only endure severe conditions but also maintained their functional integrity post-exposure. For instance, Ensifer meliloti retained its ability to form beneficial nodules on plant roots and convert nitrogen to ammonia even after exposure to temperatures up to 50 degrees Celsius.
In another finding, the formulation containing E. coli Nissle 1917 inhibited the growth of Shigellaflexneri, a leading cause of fatal diarrhea in low- and middle-income countries, during lab dish experiments.
Last year, various strains of these resilient microbes were dispatched to the ISS, which Jimenez describes as “the ultimate stress test.”
“Every aspect—from shipping on Earth to preflight validation and storage up to the launch—was part of this rigorous evaluation, especially lacking temperature control along the journey,” he adds.
The samples have since returned to Earth, and Jimenez’s team is currently analyzing them. He intends to compare the microbes kept inside the ISS with those exposed to the external environment and other control samples maintained on Earth.
“This research paves the way for enhanced stability of probiotics and genetically modified microbes in extreme environments like outer space, potentially aiding astronaut health and ensuring sustainable food production through resilient crops,” says Camilla Urbaniak, a research scientist at NASA’s Jet Propulsion Laboratory who was not part of the study.
This research received support from NASA’s Translational Research Institute for Space Health, Space Center Houston, MIT’s Department of Mechanical Engineering, the 711 Human Performance Wing, and the Defense Advanced Research Projects Agency.
Additional contributors to the study include Johanna L’Heureux, Emily Kolaya, Gary Liu, Kyle Martin, Husna Ellis, Alfred Dao, Margaret Yang, Zachary Villaverde, Afeefah Khazi-Syed, Qinhao Cao, Niora Fabian, Joshua Jenkins, Nina Fitzgerald, Christina Karavasili, Benjamin Muller, and James Byrne.
Photo credit & article inspired by: Massachusetts Institute of Technology
