Led by Prof. Dr. Ralf Moeller
Life can be found everywhere on our planet, even in the most harmful of environments where human life would be impossible. In fact, microorganisms have been found to thrive from the permafrost of Antarctica to the driest places in the Atacama Desert. In artificial environments such as the International Space Station (ISS) the presence of microbes both inside and outside of the ISS can be a threat to health and planetary protection. But this could also provide an opportunity to study and maintain the ecological biome of the ISS or to produce products of interest, such as vitamins or food conservatives.
The Space Microbiology Research Group studies how microorganisms survive and adapt to real and simulated space conditions, such as microgravity, radiation, vacuum, extreme temperature fluctuations, desiccation, etc. This is to examine microorganisms grown and isolated onboard the ISS and to compare them with their relative counterparts from Earth. We conduct ground-based studies investigating the effect of space conditions on the growth and survivability of microorganisms.
As part of the radiation biology department, our expertise is studying the effect of radiation on microorganisms. On Earth, most radiation is absorbed by our electromagnetic field, but in space the only protection are a few centimeters of composite materials, mainly aluminum. Attached to space hardware on the outside of the ISS is where only the most radiation and vacuum resistant spore-forming microorganisms are able to survive the impact of a broad spectrum of UV-radiation as well as cosmic and galactic radiation. We determine the impact of radiation and its repair at the molecular level to further investigate DNA-repair mechanisms shielding proteins and pathways.
What microorganisms are we working with?
Currently our lab is working mainly with three different model organisms: the bacterium Bacillus subtilis and the filamentous fungi Penicillium sp. and Aspergillus sp.
B. subtilis is capable of forming highly resistant endospores upon nutrient deprivation. They can survive harsh environmental conditions such as UV radiation, oxidative stress, heat, chemicals, and vacuum. Their high resistance is conferred by (i) the complex structure of the multi-layered spore coat, (ii) spore-specific sophisticated DNA protection and (iii) highly efficient DNA repair mechanisms during spore revival. Due to their extreme resistance, bacterial spores have a high potential of unintentionally being transferred to another planet or moon by space missions. Avoiding this contamination is one of the key aspects of ‘Planetary Protection’ and requires efficient sterilization measures for spacecraft and space vehicles. In this context, spores are often used as biological indicators to validate the effectiveness of sterilization processes in space industry.
To increase its chances of survival, B. subtilis can not only form resistant spores, but also highly structured surface-associated communities called biofilms. Biofilm formation protects the individual cell from negative environmental conditions (e.g. salt, antibiotics, temperature, shear forces, and radiation) and the close proximity to the substrate increases accessibility to nutrients, water and minerals.
A: Top view of an approx. 1 cm Bacillus subtilis biofilm
B: Cross-section of a 40 h old Bacillus subtilis biofilm
C: Fluorescence microscopic picture of Bacillus subtilis cells (4 h after germination)
D: Water forms spherical droplets on the hydrophobic surface of Bacillus subtilis biofilms
When identifying what “space microbes” were contaminating the ISS, two main fungal genera are dominant: Aspergillus and Penicillium. These are most commonly known as mold, which has been found growing on the walls, windows, air filtration systems, water and urine systems, and even lettuce that was grown onboard the ISS.
Additionally, filamentous fungi like P. rubens and A. niger can also form biofilms. Fungal biofilms are one of the main causes of infections and can be found on our teeth, in industrial water systems or on medical instruments, such as catheters. But, they can be useful and good, too! Filamentous fungi are also the main producers of antibiotics, vitamins and food supplements in the biotechnological industry nowadays. Understanding how filamentous fungi grow and colonize the ISS and other enclosed habitats such as hospitals will help us monitor, control and use them to their full potential, both on Earth and in space.
A: Fluorescence microscopic picture of a Penicillium rubens biofilm attached to an aluminum coupon
B: Phase contrast microscopic picture of an Aspergillus niger microcolony
C: Top view of a colony of Aspergillus versicolor
D: Phase contrast microscopic picture showing the general features of hyphae from Aspergillus niger