MIT engineers develop method to shield microbes from harsh conditions

Last year, several strains of the extremophile microbes survived a trip to the International Space Station. Credit: Warren "Woody" Hoburg, NASA.

Microbes play a crucial role in various applications, including health, agriculture, and even space missions.

However, these tiny organisms often face extreme conditions that can damage or destroy them.

To address this issue, MIT researchers have developed an innovative method to protect microbes, making them resilient enough to endure harsh environments.

The MIT team created a technique that mixes bacteria with food and drug additives approved by the FDA as “generally regarded as safe.”

By experimenting with different combinations, the researchers identified formulations that stabilize several types of microbes, including yeast and bacteria.

These special formulations help the microbes survive high temperatures, radiation, and industrial processes that typically harm unprotected microbes.

Microbes in Space

In a remarkable test, some of these microbes were sent to the International Space Station (ISS) to see if they could withstand the extreme conditions of space.

Space Center Houston Manager of Science and Research, Phyllis Friello, coordinated the mission.

The microbes have recently returned to Earth, and the researchers are now analyzing their survival and stability.

Broader Applications

“This project aims to stabilize organisms for extreme conditions, with applications ranging from space missions to human health and agriculture,” explains Giovanni Traverso, an associate professor of mechanical engineering at MIT and a gastroenterologist at Brigham and Women’s Hospital. Traverso, the senior author of the study, highlights the broad potential of their work.

The lead author of the paper, which appears in Nature Materials, is Miguel Jimenez, a former MIT research scientist now an assistant professor of biomedical engineering at Boston University.

Surviving Harsh Conditions

About six years ago, Traverso’s lab, funded by NASA’s Translational Research Institute for Space Health (TRISH), began exploring ways to make helpful bacteria, such as probiotics and microbial therapeutics, more resilient. Initial analysis of 13 commercially available probiotics revealed that six of them did not contain as many live bacteria as advertised.

“What we found was that, perhaps not surprisingly, there is a difference, and it can be significant,” says Traverso. “So the next question was, given this, what can we do to help the situation?”

Selecting Microbes for Testing

The researchers chose four microbes for their experiments: three types of bacteria and one yeast. These included:

  1. Escherichia coli Nissle 1917: A probiotic used to treat traveler’s diarrhea.
  2. Ensifer meliloti: A bacterium that helps plants grow by fixing nitrogen in soil.
  3. Lactobacillus plantarum: A bacterium used in food fermentation.
  4. Saccharomyces boulardii: A yeast used as a probiotic.

When microbes are used for medical or agricultural purposes, they are usually dried into a powder through lyophilization.

However, making them into more useful forms like tablets or pills is challenging because the process involves toxic solvents. The MIT team sought additives to improve the microbes’ survival during this process.

Developing Protective Additives

“We developed a workflow using materials from the FDA’s ‘generally regarded as safe’ list, mixing them with bacteria to see which combinations enhance stability during lyophilization,” Traverso explains.

Their experiments showed that different ingredients, mainly sugars and peptides, worked best for each type of microbe. They then optimized one microbe, E. coli Nissle 1917, finding that a mixture of caffeine or yeast extract with a sugar called melibiose created a highly stable formulation.

This mixture, named formulation D, maintained over 10% survival rates after six months at 37°C, while a commercial version lost all viability after just 11 days.

Formulation D also withstood high radiation levels, up to 1,000 grays, far exceeding typical Earth and space radiation doses.

The exact mechanism of how these formulations protect bacteria remains unknown, but researchers believe the additives may help stabilize bacterial cell membranes during rehydration.

The researchers demonstrated that these resilient microbes not only survive harsh conditions but also retain their functionality. For example, Ensifer meliloti continued to support plant growth after exposure to 50°C.

Last year, various strains of these hardy microbes were sent to the ISS, described by Jimenez as “the ultimate stress test.” The samples have returned, and the team is now analyzing them.

“This work offers a promising approach to enhance the stability of probiotics and genetically engineered microbes in extreme environments, potentially benefiting future space missions and agricultural sustainability,” says Camilla Urbaniak, a NASA research scientist.

MIT’s groundbreaking method could pave the way for more robust applications of microbes in diverse fields, from healthcare to space exploration.