Led by Prof. Dr. Ralf Moeller
Life can be found everywhere on our planet, even in the harshest 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. Even in artificial environments such as the International Space Station (ISS), several species of microorganisms can be found. Most microorganisms come from the astronauts themselves or from equipment transported to the station. These microorganisms can be a threat to both the astronaut’s health and planetary protection. However, they also provide an opportunity to study and maintain the microbiome of the ISS and/or to produce products of interest, such as vitamins or food conservatives.
The Aerospace Microbiology Research Group studies how microorganisms survive and adapt to natural and simulated space conditions, such as microgravity, radiation, vacuum, extreme temperature fluctuations, desiccation, etc. These treatments allow us to examine microorganisms grown and isolated onboard the ISS and to compare them with their relative counterparts from Earth. We conduct ground-based studies to investigate 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. Only the most radiation- and vacuum-resistant spore-forming microorganisms can live on the outside of ISS space hardware, where they survive the impact of a broad spectrum of UV-radiation as well as cosmic and galactic radiation. We determine effects of radiation and its repair at the molecular level to further investigate DNA-repair mechanisms shielding proteins and pathways.
Biofilm forming Staphylococci and antimicrobial surfaces
Microbial biofilms are considered a risk because they can damage material, exhibit high resistance against antibiotics and disinfectants, and can be potentially pathogenic. In spaceflight, biofilms are particularly dangerous because the process of cleaning and removing biofilms in a space station, such as the International Space Station (ISS), is even more challenging than on earth. Additionally, biofilms can jeopardize the astronaut’s health due to the reduced function of their immune system in the space environment. Having a sterile environment in manned space flight is impossible because microorganisms are a fixed component of the human body; species of the genus Staphylococcus (e.g. Staphylococcus capitis subsp. capitis) have already been isolated from the ISS. One of our research goals is to characterize growth and biofilm formation of Staphylococci in space conditions, which includes desiccation, microgravity and increased radiation.
A method for decreasing the spreading of microorganisms aboard a space station could be the use of antimicrobial surfaces. We investigate the effectiveness of antimicrobial surfaces, such as copper surfaces, against the attachment and biofilm formation of Staphylococci under space conditions.
A SEM image of a Staphylococcus capitis subsp. capitis biofilm on a steel surface (Image: Michael Laue, RKI Berlin)
B SEM image of Staphylococcus capitis subsp. capitis cells (Image: Michael Laue, RKI Berlin, Germany)
C Growth of Staphylococcus capitis subsp. capitis on Mannitol Salt Phenol Red Agar
D DLIP structured copper plate (Manufactured by: FuWe, Saarland University)
Skin microbiome under space conditions
The characterization of the human skin microbiota is crucial. An imbalance of skin flora can have significant implications for both human health and the surrounding environment in space. The ISS represents a closed living space that is strongly affected by microorganisms. Human skin and the intestinal tract are the major sources of microorganisms within this artificially created environment. Skin can also harbor and transmit contaminants.
The Artificial Gravity Bed Rest Study with ESA (AGBRESA) provides an appropriate setting to perform characterizations of the microbiome. In the course of physiological adaptation processes during this artificially simulated microgravity, a displacement of body fluids occurs towards upper body section. Similar effects have also been observed with astronauts during long-term stays in space, where they develop a so-called puffy face. According to these adaptations, it is assumed that micro-environmental conditions of the skin such as pH, moisture and sebum levels may change. The question is whether skin microorganisms also adapt, and if so, what threats might they pose to human health and the artificial materials of space habitats.
A Sampling for microbiome analysis applied by swabbing of a test subjects’ forehead during the head-down tilt stage
B Exemplary forehead swab sample plated on Columbia blood agar after an incubation of 24 hours at 37°C
C Handprint on solid growth medium
D Measurement of the moisture content of a test subjects’ ear during the head-down tilt stage
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! Currently, filamentous fungi are the main producers of antibiotics, vitamins and food supplements in the biotechnological industry. 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 Top view of a colony of Aspergillus niger melanin mutant with fawn-colored spores
C Fluorescent microscopy of Aspergillus niger hyphae, stained with Calcofluor white (stains chitin component of the cell wall)
D Scanning electron microscopy (SEM) pictures with an overview of Aspergillus niger colony cross-section
E SEM image of a conidiophore cross-section
F SEM image of the highly-pigmented spores with a thick cell wall
Decontamination and prevention of the formation of fungal biofilms
Our research aims to decrease the risks of fungal growth in closed environments, especially to apply in aviation, spaceflight and medical institutions. In order to find possibilities for both efficient decontamination and targeted preventions against mold, we conduct investigations of plasma sterilization and antifungal surface development. Further, we are establishing assays to test the antifungal properties of insulation materials. By identifying antifungal insulation materials, we may be able to develop a crucial “first barrier” against mold that protects inner walls from humidity and doesn’t give fungal spores a chance to grow.
A Black Mold (Aspergillus niger) on conventional mineral wool, which is commonly used as insulation material (RKI Berlin, Germany)
B Black Mold (Aspergillus niger) on Organic Resorcinol-Formaldehyde-Aerogel
C Light microscopy image of untreated Silica Aerogel insulation material
D Light microscopy image of Aspergillus niger growth on Silica Aerogel insulation material