Microbes in Space

Written by Arushi Singh

The Microbes in Space seminar, co-sponsored by the Maryland Branch of the American Society for Microbiology, highlighted projects conducted in space relating to microbiology. Seminar attendees were joined by Dr. Jennifer Kerr of Notre Dame of Maryland University to present on some key studies happening in space and her own lab’s research.

Kerr first highlighted the many hazards spaceflight has on the human body. These dangers include radiation which damages DNA and lack of gravity which leads to mineral and bone loss. Therefore it is quite astonishing how certain microorganisms can withstand these obstacles, in particular tardigrades. Also known as water bears or moss piglets, tardigrades are tiny and cute invertebrates which prefer to live in water. They are well known for cryptobiosis, Latin for “hidden life”. Cryptobiosis is when there are no signs of metabolic activity, but the organism is still alive. In this state these animals only maintain 0.01% of normal metabolic activity which lets them handle extreme environments. Tardigrades shrivel up and go into what is known as the tun state during this dormancy period. There are also variations of cryptobiosis that tardigrades partake in. For instance, tardigrades in the tun state could survive 125 years without water (anhydrobiosis).

Tardigrade space research began in 2007 with the NASA Foton-M3 Mission studying radiation’s effects on these tiny critters. In a 2019 study, tardigrades in the tun state accidentally crash landed on the moon! Now, is it likely that there is a colony of tardigrades on the moon since there is no water on the moon and those tardigrades arrived in the tun state? Well, a 2021 study investigated tardigrade survival in such high-speed crashes. It was found that moss piglets could survive the impact, but not the shock pressure withstood, so it is unlikely that there is a tardigrade colony on the moon.

Aside from cute water bears, there are also more general microbiome studies happening in space. Specifically, these studies depict how contact surfaces around the International Space Station (ISS) have changed in response to the astronauts who come and go on the Space Station. The microbiomes of crewmembers may influence the microbial composition of ISS habitable surfaces. This is important in managing disease control and preventing contaminants from breaking certain hardware on the ISS. It was found that an astronaut’s microbiome contributes to roughly 55% of the environmental surface microbiome. These findings were not startling, yet it was importantly confirmed that the majority of these were safe and typical bacteria that already exists on the skin. However some were classified as opportunistic pathogens. Opportunistic pathogens have the potential to cause disease, but are unlikely to do so when kept in check by other bacteria or if the person’s immune system is properly functioning. Furthermore, this microbiome snapshot was maintained for a few weeks even after the particular astronaut had left. However this micro-diversity encountered turnover when a new astronaut arrived at the space station and was in constant interplay.

Not only did the microbiomes on ISS surfaces change, even the astronauts who lived there had notable shifts in their own microbial environments. In particular there were 347 bacterial species identified. This varied based on sample sites from the saliva, ears, skin, and nostrils. There were 12 top genera with the highest relative abundance identified across these astronaut samples. Mainly differences were seen in skin samples when astronauts were in flight to and from the Space Station. In the mouth, there were some key, but minimal changes. For instance, saliva had the largest change in composition of bacteria but relative abundance (which is the overall number of bacterial species) stayed the same. One potentially concerning finding with the saliva organisms was that some of them sampled displayed antimicrobial resistant gene markers. The reasoning is unknown, but further research is ongoing.

The NASA Biomedical Engineering for Exploration Space Tech (BEEST) lab is researching health care for exploration. Their goal is to train astronauts in non-invasive treatment of dental cavities. Seminar attendees were also shown a light-hearted video on how astronauts brush their teeth in space. Something as simple as brushing their teeth is even more important in space. There has never been an astronaut who is a dentist, so having preventative care and training is important. Astronauts are even taught techniques up to tooth extraction.

A healthy microbiome is known to be in eubiosis while an unbalanced one is in dysbiosis. For example, the reason that too much sugar leads to tooth decay is because bacteria in the mouth feed on this excess sugar. It causes them to grow more and create more acid. This excess acid leads to a pH shift in which creates a habitable environment for more hardy bacteria to in turn create more acid. This acid also destroys tooth enamel. This leads to cavities and even more body-based diseases. For instance, the dangerous bacteria from the mouth can move through blood to other bodily systems and clog arteries. Maintaining oral hygiene is of utmost priority in space.

This human-microbial research ties back to Dr. Jennifer Kerr’s research at Notre Dame. She is an oral microbiologist and studies teeth in space. Her work centers around Streptococcus mutans. Her lab hopes to help astronauts identify a cavity and use a handheld microwave device to kill the bacteria. Astonighly when this gadget is held to the mouth for only a minute, 99% of the S. mutans are killed. However, in the case of a cavity, demineralization still remains. In order to remineralize it, the astronaut’s body needs to be given the appropriate starting material and the pH has to come back to neutral. This research is still ongoing, but it could have profound impacts, not only on human health in space but even on Earth. According to the Global Burden of Disease Study “oral diseases affect close to 3.5 billion people worldwide” which is why this research and its findings will be so consequential to the world of dentistry and the science and medical communities as a whole.

Co-sponsored by the Maryland Branch of the American Society for Microbiology.