Ralf Moeller

Ralf Moeller
German Aerospace Center (DLR) | DLR · Abteilung für Radiation Biology

Professor
Microbiome research, Space microbiology (bacteriology, virology), ISS experiments

About

250
Publications
36,623
Reads
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3,146
Citations
Citations since 2016
159 Research Items
2256 Citations
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20162017201820192020202120220100200300400
20162017201820192020202120220100200300400
20162017201820192020202120220100200300400

Publications

Publications (250)
Article
Full-text available
Previous studies have reported that spaceflight specific conditions such as microgravity lead to changes in bacterial physiology and resistance behavior including increased expression of virulence factors, enhanced biofilm formation and decreased susceptibility to antibiotics. To assess if spaceflight induced physiological changes can manifest in h...
Article
In the last decades, Mars has been widely studied with on-site missions and observations, showing a planet that could have hosted life in the past. For this reason, the recent and future space missions on the red planet will search for traces of past and, possibly, present life. As a basis for these missions, Space Agencies, such as the European Sp...
Article
The effect of a Mars-like UV flux and γ-radiation on the detectability of biomarkers in dried cells of Chroococcidiopsis sp. CCMEE 029 was investigated using a fluorescence sandwich microarray immunoassay. The production of anti-Chroococcidiopsis antibodies allowed the immunoidentification of a reduced, though still detectable, signal in dried cell...
Article
Full-text available
The biotechnology- and medicine-relevant fungus Aspergillus niger is a common colonizer of indoor habitats such as the International Space Station (ISS). Being able to colonize and biodegrade a wide range of surfaces, A. niger can ultimately impact human health and habitat safety. Surface contamination relies on two key-features of the fungal colon...
Article
Full-text available
The question about the stability of certain biomolecules is directly connected to the life-detection missions aiming to search for past or present life beyond Earth. The extreme conditions experienced on extraterrestrial planet surface ( e.g. Mars), characterized by ionizing and non-ionizing radiation, CO 2 -atmosphere and reactive species, may des...
Article
Biofilms are problematic on Earth due to their ability to both degrade the materials upon which they grow and promote infections. Remarkably, 65% of infections and 80% of chronic diseases on Earth are associated with biofilms. The impact of biofilms is even greater in space, as the crew's lives and mission success depend on nominal operation of mec...
Conference Paper
BIOLEX (BIOlogy and Lunar EXperiments) tries to fulfil a large number of scientific investigations in reference to Astrobiology and Space Life Sciences. In situ Measurement operations through spectrometers (such as Raman, IR, UV/VIS and environmental sensors) on an exposure platform designed as a LOGOS cube (Lunar Organisms, Geo-microbiology and Or...
Article
When the Artemis missions launch, NASA's Orion spacecraft (and crew as of the Artemis II mission) will be exposed to the deep space radiation environment beyond the protection of Earth's magnetosphere. Hence, it is essential to characterize the effects of space radiation, microgravity, and the combination thereof on cells and organisms, i.e., to qu...
Article
Metal complexes of porphyrins and porphyrin-type compounds are ubiquitous in all three domains of life, with hemes and chlorophylls being the best-known examples. Their diagenetic transformation products are found as geoporphyrins, in which the characteristic porphyrin core structure is retained and which can be up to 1.1 billion years old. Because...
Article
If life ever appeared on Mars and if it did refuge into sub-superficial environments when surface conditions turned too hostile, then it should have been periodically revived from the frozen, dormant state in order to repair the accumulated damage and reset the survival clock to zero for the next dormant phase. Thus, unravelling how long Earth dorm...
Article
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Maintaining crew health and safety are essential goals for long-term human missions to space. Attaining these goals requires the development of methods and materials for sustaining the crew’s health and safety. Paramount is microbiological monitoring and contamination reduction. Microbial biofilms are of special concern, because they can cause dama...
Article
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Viruses constitute a significant part of the human microbiome, so wherever humans go, viruses are brought with them, even on space missions. In this mini review, we focus on the International Space Station (ISS) as the only current human habitat in space that has a diverse range of viral genera that infect microorganisms from bacteria to eukaryotes...
Conference Paper
Full-text available
As space agencies plan to expand human presence in space and to settle on the Moon first and Mars later, developing strategies to achieve this goal in a sustainable way is necessary. These include in situ resource utilization (ISRU) and recovering of materials by waste recycling (1). Microbe based technologies may be pivotal to the success of human...
Article
Full-text available
Radiation of ionizing or non-ionizing nature has harmful effects on cellular components like DNA as radiation can compromise its proper integrity. To cope with damages caused by external stimuli including radiation, within living cells, several fast and efficient repair mechanisms have evolved. Previous studies addressing organismic radiation toler...
Conference Paper
Introduction: Long-term space missions are accompanied by harmful environmental conditions like microgravity. Due to the reduced gravity, astronauts adapt to their environment resulting in tissue fluidic shifts. Since the knowledge about microbiome data in space is sparse and conduction of experiments at the ISS is complex, suitable analogs are nee...
Conference Paper
Long term human space missions require efficient strategies to sustain crew health and safety. This is why we need to develop improved spaceflight-suitable methods for microbiological monitoring and contamination control. Especially microbial biofilms are of concern in spaceflight because they can damage equipment by polymer deterioration, corrode...
Article
Full-text available
As humans explore and settle in space, they will need to mine elements to support industries such as manufacturing and construction. In preparation for the establishment of permanent human settlements across the Solar System, we conducted the ESA BioRock experiment on board the International Space Station to investigate whether biological mining co...
Article
In article 2001656, Daniel W. Müller and co‐workers were able to significally enhance antibacterial efficiency of Cu surfaces against Escherichia coli by ultrashort pulsed laser interference patterning in the scale of single bacteria cells. Improved bacterial killing could mainly be attributed to increased Cu sensitivity due to altered contact situ...
Article
Remarkably, we know more about the radiation environment onboard the International Space Station than we do about radiation values at altitudes between 30-40 km in the middle stratosphere. Within this work, we provide data about the radiation dose measured during two consecutive balloon flights flown within a 4-month timeframe over New Mexico and A...
Presentation
The ability of terrestrial life to survive in the Martian environment is of particular interest for both planetary protection measures and for future colonization endeavors. Many studies have examined bacterial spore survival and decontamination, however, little is known about fungal spore resistance properties. To understand the survival potential...
Article
Full-text available
Whether terrestrial life can withstand the martian environment is of paramount interest for planetary protection measures and space exploration. To understand microbial survival potential in Mars-like conditions, several fungal and bacterial samples were launched in September 2019 on a large NASA scientific balloon flight to the middle stratosphere...
Article
Full-text available
Copper (Cu) exhibits great potential for application in the design of antimicrobial contact surfaces aiming to reduce pathogenic contamination in public areas as well as clinically critical environments. However, current application perspectives rely purely on the toxic effect of emitted Cu ions, without considering influences on the interaction of...
Article
Full-text available
Among the celestial bodies in the Solar System, Mars currently represents the main target for the search for life beyond Earth. However, its surface is constantly exposed to high doses of cosmic rays (CRs) that may pose a threat to any biological system. For this reason, investigations into the limits of resistance of life to space relevant radiati...
Article
Full-text available
Microorganisms are employed to mine economically important elements from rocks, including the rare earth elements (REEs), used in electronic industries and alloy production. We carried out a mining experiment on the International Space Station to test hypotheses on the bioleaching of REEs from basaltic rock in microgravity and simulated Mars and Ea...
Article
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Extremophiles are optimal models in experimentally addressing questions about the effects of cosmic radiation on biological systems. The resistance to high charge energy (HZE) particles, and helium (He) ions and iron (Fe) ions (LET at 2.2 and 200 keV/µm, respectively, until 1000 Gy), of spores from two thermophiles, Bacillus horneckiae SBP3 and Bac...
Article
Full-text available
Microorganisms perform countless tasks on Earth and they are expected to be essential for human space exploration. Despite the interest in the responses of bacteria to space conditions, the findings on the effects of microgravity have been contradictory, while the effects of Martian gravity are nearly unknown. We performed the ESA BioRock experimen...
Article
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Article
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Space exposure experiments from the last 15 years have unexpectedly shown that several terrestrial organisms, including some multi-cellular species, are able to survive in open space without protection. The robustness of bdelloid rotifers suggests that these tiny creatures can possibly be added to the still restricted list of animals that can deal...
Article
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One of the primary current astrobiological goals is to understand the limits of microbial resistance to extraterrestrial conditions. Much attention is paid to ionizing radiation, since it can prevent the preservation and spread of life outside the Earth. The aim of this research was to study the impact of accelerated He ions (150 MeV/n, up to 1 kGy...
Article
Full-text available
Experiments are performed to assess the inactivation of Bacillus subtilis spores using a non-thermal atmospheric-pressure dielectric barrier discharge. The plasma source used in this study is mounted inside a vacuum vessel and operated in controlled gas mixtures. In this context, spore inactivation is measured under varying nitrogen/oxygen and humi...
Article
Full-text available
Carotenoids are promising targets in our quest to search for life on Mars due to their biogenic origin and easy detection by Raman spectroscopy, especially with a 532 nm excitation thanks to resonance effects. Ionizing radiations reaching the surface and subsurface of Mars are however detrimental for the long-term preservation of biomolecules. We s...
Article
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The filamentous fungus Aspergillus niger is one of the main contaminants of the International Space Station (ISS). It forms highly pigmented, airborne spores that have thick cell walls and low metabolic activity, enabling them to withstand harsh conditions and colonize spacecraft surfaces. Whether A. niger spores are resistant to space radiation, a...
Article
Spores of a variety of bacteria are resistant to common decontamination agents, and many of them are major causes of food spoilage and some serious human diseases, including anthrax caused by spores of Bacillus anthracis . Consequently, there is an ongoing need for efficient methods for spore eradication, in particular methods that have minimal del...
Chapter
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Fungi have been companions of mankind for millennia. Mushrooms inspired our eating culture, and yeasts and filamentous fungi were developed into highly efficient cell factories during the last 100 years to produce many products utilized in different industries worldwide. What more is to come in the next 100 years? We propose here that fungi can bec...
Poster
Microorganisms such as archaea, bacteria, viruses, yeast and filamentous fungi (known as “mold”) are an integral part of our human body and our natural environment on Earth. When human space exploration started at around 1961, microbial life has been brought along with astronauts across terrestrial borders and to our space stations Mir (Russian Spa...
Article
Full-text available
Regarding future space exploration missions and long-term exposure experiments, a detailed investigation of all factors present in the outer space environment and their effects on organisms of all life kingdoms is advantageous. Influenced by the multiple factors of outer space, the extremophilic bacterium Deinococcus radiodurans has been long-terml...
Conference Paper
Long-term human missions to space require methods for sustaining the health and safety of the crew. Therefore, microbiological monitoring and reduction of contamination is necessary. Microbial biofilms are of special interest because they can cause damage to spaceflight equipment and are difficult to eliminate due to their increased resistance to a...
Conference Paper
Gravity is the most consistent physical parameter to which all life has so far been subordinated and has not changed from the beginning of evolution to the present day. Since Apollo 16 the Gram-positive bacterium Bacillus subtilis has been used to study the influence of gravity on vegetative cells, spores and biofilms and still it remains unclear t...
Conference Paper
Einleitung: Ob es die Rückkehr zum Mond oder der erste Schritt auf dem Mars ist, den Menschen wird es in Zukunft immer wieder und immer weiter ins Weltall führen. Um die Auswirkungen der im Weltraum herrschenden Umweltbedingungen, wie etwa Schwerelosigkeit, zu simulieren, werden aufwändige terrestrische Studien durchgeführt. Das Deutsche Zentrum fü...
Article
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Bacillus subtilis spore inactivation mechanisms under low energy electron beam (LEEB) and high energy electron beam (HEEB) treatment were investigated using seven mutants lacking specific DNA repair mechanisms. The results showed that most of the DNA repair-deficient mutants, including ΔrecA, ΔKu ΔligD, Δexo Δnfo, ΔuvrAB and ΔsbcDC, had reduced res...
Poster
The cold, arid, remotely located and perennially ice covered environment of the Antarctic ice sheet is the most hostile place on Earth. It has long been considered an analogue to how life might persist in the frozen landscape of the major Astrobiological targets of our solar system such as Mars or the Jupiter’s ice-covered moon Europa. In the frame...
Conference Paper
The exposure to the space radiation environment remains a major limiting factor for human long-duration space missions and permanent presence in space habitats due to its high biological effectiveness and the difficulties to effectively shield the radiation. The next decade in human spaceflight will be characterized by a continuous presence of huma...
Article
In den letzten Jahrzehnten lag der Schwerpunkt der bemannten Raumfahrt auf Missionen im erdnahen Orbit. Die deutsche Raumfahrtmedizin hat sich dabei auf wissenschaftliche Entwicklungen und Anwendungen konzentriert, die Erkenntnisse für das Leben auf der Erde generieren. Zurzeit geschehen diese Missionen ausschließlich auf der Internationalen Raumst...
Poster
Aspergillus niger, the model organism for modern biotechnology, is one of the predominant fungus detected aboard the Russian Space Station (Mir) as well as the International Space Station (ISS) [1]. The ability of fungi to colonize a variety of solid and liquid substrates in the stations indoor-closed habitat – e.g. walls, windows, life-support sys...
Article
Microbial contamination of human-tended spacecraft is unavoidable, making the study of microbial growth under space conditions essential for the preservation of astronauts' health and equipment integrity. Previous studies suggested that spaceflight conditions, such as microgravity, cause a range of physiological microbial alterations including incr...
Presentation
Full-text available
Filamentous fungi such as Aspergillus and Penicillium sp. (also known as “mold”) represent some of the predominant contaminations found onboard the Mir (Russian Space Station) and the International Space Station (ISS). Aspergillus sp. have been found in NASA clean rooms belonging to Johnson Space Center Curation Laboratory as well as in spacecraft...
Poster
Fungi are able to colonize indoor-closed habitats such as space stations, in a variety of solid and liquid substrates – e.g. walls, windows, life-support systems, etc. Their growth is usually associated with material degradation and spore formation, which can pose a threat to both astronauts’ health and spacecraft safety, in particular when in long...
Article
The Planetary Society's Phobos Living Interplanetary Flight Experiment (Phobos LIFE) flew in the sample return capsule of the Russian Federal Space Agency's Phobos Grunt mission and was to have been a test of one aspect of the hypothesis that life can move between nearby planets within ejected rocks. Although the Phobos Grunt mission failed, we pre...
Conference Paper
Full-text available
Introduction: For risk assessment, the mutagenic potential of the heavy ion component of the galactic cosmic radiation is of major concern for tumor induction as radiation late effects. The genetically modified TA1535 Salmonella typhimurium strain (SWITCH) reports on the presence of genotoxic conditions by dose dependent increase of bioluminescence...
Conference Paper
Introduction: One definition of life is a “selfsustaining system capable of Darwinian evolution”. Thus, the ability to measure evolution is highly relevant to the search for life beyond Earth (Neveu et al. 2018). We previously discussed potential space experiments to measure evolution using nanopore sequencing in a satellite, on/in the Internationa...
Presentation
Introduction: Aspergillus sp. was one of the predominant fungal genera detected aboard the Russian Space Station (Mir) as well as the International Space Station (ISS) (Checinska et al. 2015). As spore formers, filamentous fungi such as Aspergillus can pose a threat to astronauts’ health and to planetary protection (Ramage et al. 2011). Experiments...
Conference Paper
The exposure to the space radiation environment remains a major limiting factor for human long-duration space missions due to its high biological effectiveness and the difficulties to effectively shield the radiation. The next decade in human spaceflight will be characterized by a continuous presence of human beings in Low Earth Orbit (LEO), by the...
Conference Paper
An enduring human presence in space is required to achieve many goals of ESA´s and NASA´s space programs. During long-term missions, astronauts are exposed to various conditions such as microgravity, radiation, sleep-disruption, insufficient nutrition and also microbial contamination. Since astronauts´ immune function is compromised, all these fact...
Article
The human body houses a large number of diverse outnumbering other organisms such as archaea and fungi bacteria by orders of magnitude. The whole community of organisms is commonly referred to as human microbiota, whereas microbiome is defined as the collective genomes of these organisms. Whereas earlier estimates suggested that the number of bacte...
Article
Full-text available
In a Mars exploration scenario, knowing if and how highly resistant Bacillus subtilis spores would survive on the Martian surface is crucial to design planetary protection measures and avoid false positives in life-detection experiments. Therefore, in this study a systematic screening was performed to determine whether B. subtilis spores could surv...
Article
Previous work indicates that dormant Bacillus subtilis spores have many hundreds of mRNAs, some of which are suggested to play roles in spores’ “return to life” or revival. The present work finds only ∼46 mRNAs at ≥1 molecule spore, with others in only fractions of spores in populations, often very small fractions. Less-abundant spore mRNAs are not...