Humans have used brewer’s yeast for millennia to make delicious beer. And despite the fact that it's a microorganism, we have far more in common with the yeast than you might think. In fact, scientists are sending the organism into space to study how it reacts to radiation — and they think these results can hint at how humans will fare during longer space travel, too.
A significant danger of space travel is cosmic radiation. This invisible bombardment of heavy and high-energy subatomic particles, released by the universe’s most dynamic displays such as solar flares and supernovas, can cause damage to the human body. If humans are ever going to take longer trips in space, say to Mars, we’ll need to figure out how to get there without damaging our bodies.
Unfortunately, cosmic radiation is hard to replicate in a laboratory. This makes studying its damaging effects a challenge. In an effort to better understand how this form of radiation will impact humans who journey far outside the cocoon-like magnetic field environment surrounding Earth, scientists have placed two strains of brewer’s yeast — also known as Saccharomyces cerevisiae — into cartridges to fly on NASA’s upcoming BioSentinel mission, which is tentatively scheduled for later this year.
How can brewer’s yeast help us understand astronauts’ health?
For thousands of years, we’ve played alcohol alchemy with brewer’s yeast. In fact, S. cerevisiae can be traced as far back as 3,150 B.C. to an ancient Egyptian wine jar, and today it’s commercially used to make beer.
Beyond its bubbly benefits, it turns out this single-celled organism is also a great analog for the human body. NASA considers S. cerevisiae a fantastic stand-in for our cells. In particular, this yeast repairs DNA damage — one major consequence of radiation — in a similar way to how human cells do it.
How it works — BioSentinel will hitch a ride aboard NASA’s Artemis 1 mission, the first major leg of the space agency’s highly-anticipated return to the Moon, launching sometime later this year.
Artemis will last roughly three weeks, but BioSentinel will stay in space for much longer. NASA hopes the high-flying brewer’s yeast will reveal new information on how cosmic radiation might affect its astronauts, such as the ones traveling on the Artemis 2 mission; they’ll be the first people to reach the Moon since the Apollo era.
S. cerevisiae is also convenient to use onboard a space mission because it can remain alive while it is dry and inactive. BioSentinel is housed in a CubeSat, a cereal-box-sized satellite that will detach from Artemis’ rocket once it reaches the Moon. Once detached, it will fly past the Moon to orbit the Sun.
Scientists can control the activity of the yeast and the accompanying experiments within the CubeSat remotely. Specifically, they will rehydrate the yeast and perk it up once it’s out there, helping the team to get accurate deep-space exposure readings.
In total, BioSentinel will take a 6-month trip outside the protection of Earth’s magnetic field. Instruments on board the spacecraft will inject fluids and sugars to activate the two strains of yeast housed within cassette-like containers called microfluidics cards. One key part of the research involves dyes that change colors as the yeast metabolizes.
Biosentinel is broadening its scope by sending two versions of S. cerevisiae, including a robust strain, and one sensitized strain that is missing a DNA-repairing gene.
Why it matters — Cosmic radiation is all around. “Just imagine yourself sitting in free space, and you’re being hit from every single direction all the time,” Sergio Santa Maria, lead project scientist on BioSentinel, tells Inverse.
Santa Maria first saw how the environment can influence genetics in his home country of Peru.
As an undergrad student, he met miners working in the Andean highlands just outside of Lima. After running an experiment that analyzed samples of their blood, he found traces of chromosomal changes. Occupational hazards — exposure to certain metals, the exhaust of diesel machinery, and ultraviolet rays from their high-elevation location in these mountains — were the likely culprit. Now, Santa Maria is tackling the work safety of another profession.
Astronauts in deep space face two major radiation sources. One is the Sun. Our neighborhood star releases a steady flow of photons, and this stream can occasionally become more dangerous when eruptions like solar flares and coronal mass ejections spray higher doses of these energetic subatomic particles into the Solar System.
“The problem with the solar protons is that there could be a lot of them, and they never stop,” Santa Maria, says. “They are always there.”
That’s the devil we know. But another more mysterious source of space radiation is galactic cosmic rays. These highly-energetic, heavy particles are bursting throughout the universe, born out of explosive events like supernovas.
This environment cannot be replicated on Earth, he says. A lab setting cannot show what it's like to be a living organism in space for months, being struck by space radiation simultaneously from all sides.
“Something that is important to note is that the amount of radiation, meaning the dose rate that you get in space, is not really much more than what you get within the magnetic field. It’s just the type of particles that you are being exposed to [in space] are very different, are more energetic, are heavier, and you cannot shield those as of right now,” he adds. A person in the United States gets about 5 percent of their annual radiation exposure from cosmic radiation, according to the U.S. Environmental Protection Agency.
“We are in a really good spot on Earth,” Santa Maria says, “because we are protected from many of those dangerous ones. Some of those do encounter their way into our atmosphere. But in free space, you just don’t have that luxury.”
What’s next — The Artemis 1 mission will fly on NASA’s next-generation Space Launch System (SLS) rocket. The space agency is hoping to put the rocket on its launchpad by early June to complete SLS’s last major pre-flight test that month. Teams want to perform at least two of these tests, called wet dress rehearsals, before selecting a launch date.
