Annual Conference 2025 of the Association for General and Applied Microbiology - Jahrestagung 2025 der Vereinigung für Allgemeine und Angewandte Mikrobiologie

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Prof. Dr.

Psychrophilic limits of survival – what are the implications for icy moon exploration?

FG Space microbiology

Exposing microorganisms to extreme environmental conditions can help us understand what their survival limits are. On Earth, microorganisms can be found in almost all environments, and are capable of tolerating extreme physical and chemical stressors. Investigating how these microbial extremophiles tolerate and thrive with these stressors might give us an indication of how life might survive on other planets. Several environments on Earth classified as extreme are valuable analogues which replicate the locations found on other bodies of the solar system. An interesting astrobiology location in the solar system are the icy moons Europa and Enceladus. These moons could support life due to their peculiar environment having a subsurface ocean covered by a thick ice layer. By making use of psychrophilic microorganisms which are already adapted to grow at low temperatures we can investigate whether they could hypothetical endure on the icy moons. This information might also shed light on how life could develop on the icy moons. Additionally, making use of Earth extremophiles in laboratory simulations, we can evaluate which ones might pose a threat of contamination if found to be hitchhiking on a spacecraft bound for the icy moons.The experiments initially focused on selecting four psychrophilic microbial extremophiles candidates from icy moon-analogue environments on Earth. The selected organisms Chromohalobacter sarecensis, Planococcus halocryophilus, Rhodotorula frigidalcoholis and Rhodotorula mucilaginosa, and were grown in minimal media supplemented with a single carbon source in order to represent more accurately the nutrient-limiting conditions in the subsurface ocean of the icy-moons. Following growth in minimal media we exposed the organisms to laboratory simulated extreme conditions in order to evaluate their survival limits. These conditions include: desiccation at subzero temperatures, freezing at -80°C and freezing and thawing, exposure to UV-C and polychromatic UV radiation as well as exposure to X-ray radiation. Our results highlight how all organisms can tolerate to an extent the extreme conditions, however, the yeasts are the ones which tolerate the most the conditions of desiccation and freezing and thawing. Additionally, current experiments also include the analysis of RNA extracted from yeast samples after exposure to extreme conditions to evaluate the mechanisms of repair.

Short lecture

Planetary Protection of Planet Mars – Potential risks of contamination by sulphate-reducing organisms from Earth?

Mars, commonly referred to as the Red Planet due to the red color of iron oxides present in Martian regolith, is considered the most Earth-like planet in our solar system and has fascinated humanity from for centuries. One of the key questions in Mars exploration is whether life exists or has existed on the planet. To answer this question, evidence for present or past microbial life on Mars is being sought. With the increasing number of research missions reaching Mars, planetary protection has gained significant importance to prevent contamination by terrestrial microorganisms. Endospore-forming sulfate-reducing bacteria of the family Peptococcaceae represent a group of obligate anaerobic organisms that can be found on Earth under extreme conditions in various subsurface environments including freshwater and marine sediments, mines, oil reservoirs, and aquifers at depths of up to 3,000 meters. In addition to their ability to form highly resistant endospores, they are capable of chemolithoautotrophic growth using sulfate, H2, and CO2. This characteristic, combined with their adaptability to extreme conditions, theoretically positions them as potential candidates to become stowaways to Mars and survive the harsh environment in the form of spores.In this study, two representatives of the Peptococcaceae family were investigated regarding their ability for autotrophic growth in the presence of Martian regolith and their tolerance to desiccation and radiation as present on Mars. The experiments demonstrate that the two species, Desulforamulus putei TH-11T and Desulfosporosinus lacus STP12T, can easily grow autotrophically in an H2/CO2 atmosphere using the sulfate present in the Mars regolith simulant MGS-1S as an electron acceptor. Since CO2 is part of the Martian atmosphere, water could be present occasionally and H2 could be formed through serpentinization of iron oxides where there might be a possibility that endospores who reach Mars could germinate and grow. Furthermore, we demonstrate that spores formed during growth on MGS-1S showed high resistance to an exposure to elevated temperatures, oxygen, polychromatic UV radiation and desiccation and could potentially survive dormant on Mars and may reach Mars as highly resistant contaminants of space probes. The results provide a first hint to the potential risk of contaminating Mars by spore-forming sulphate-reducing bacteria regarding topics like planetary protection and search for possible life on Mars.

Fungal biomining – In-situ resource utilization in spaceUtilizing fungi to help establish resource – efficient space missions

Filamentous fungi are powerful microorganisms for biotechnological applications. They are well-established cell factories for the production of organic acids, enzymes, and antibiotics. With the prospect of human colonization on celestial bodies such as on the Moon and Mars, the sustainability of space missions is of greater relevance and immediacy. As fungi take little demand and are tolerant towards extreme environmental conditions, it is only logical to consider them for in-situ resource utilization applications for space research. For future missions to terrestrial-like bodies such as Mars and the Moon, with surfaces that are covered abundantly with regolith, it is of high importance to establish sustainable mining applications since these bodies are great sources for ore retrieval, which is especially important since resupply missions are expensive. This study used Aspergillus simplicissimum as a model organism to determine the suitability of filamentous fungi for biomining approaches. We were able to show that our fungal species was capable of growing under simulated micro gravity conditions, as well as in the presence of Lunar Highland Simulant 1 (LHS-1) and the European Astronaut Centre Lunar Regolith Simulant (EAC-1A). Moreover, we were able to show that fungi are capable of extracting minerals and metals from lunar regolith simulants. The analysis of precipitated metals, as well as the ICP-MS analysis of the leachate, showed that several metals were dissolved in the liquid phase. The suitability of microorganisms for biomining is well known. However, to date, only applications for bacteria have been studied extensively and industrially established. This study shows that A. simplicissimum and other filamentous fungi are very promising candidates for ISRU applications in space.

Brine Beneath: The hidden microbial world of Lüneburg's salt

Environments with extremely high salt concentrations serve as analogue sites for astrobiological research. Despite their seemingly inhospitable and harsh conditions, these environments support a diverse array of extremophilic organisms. The saturated Lüneburg brine forms at a depth of 60 m below the surface through dissolution of Zechstein halite. It has been used commercially for salt extraction for over 1000 years until it was closed in 1980 and although it remains easily accessible for sampling, it had not been investigated before. Studying extremophiles from these saline habitats is important, as it offers valuable insights into a hypersaline habitat which cannot benefit from primary production through sunlight and resembles the boundaries of life on Earth and the possibility of life beyond our planet. This work provides a habitat description of the Lüneburg brine, using hydrochemical, cultivation-dependent and independent methods.The analyses included sequencing of variable regions V1-V2 and V3-V4 of the 16S rRNA gene, isolation of culturable aerobic microorganisms, enrichment of a heterotrophic and an autotrophic anaerobic microbial community as well as chemical profiling of the brine. Selected microbial isolates were tested for their resistance to astrobiological-relevant stressors. The 16S rRNA amplicon analysis identified the presence of halophilic organisms: Desulfohalobiaceae (18%), Thiohalorhabdaceae (11%) and three families from the order Halobacterales (16%). A high abundance of yet-uncultivated Nanosalinaceae (15%) were detected and recognized as promising candidates for pure culture isolation. Anaerobic enrichments demonstrated the presence of Nanosalinaceae, contingent upon substantial co-enrichment of Halobacteriaceae. Microscopic analysis indicated notable morphological diversity, with isolates displaying pleomorphism, encapsulation and biofilm production during growth. The isolates displayed tolerance towards high radiation (>500 Gy) and NaCl concentrations up to 30%, as well as enhanced growth in typically toxic perchlorates, with concentrations that are also present on Mars.The Lüneburg brine represents an aphotic habitat and thus a representative subsurface analog for other planets in outer space. It hosts a range of halophilic microorganisms capable of tolerating high radiation and salt concentrations. This study highlights the potential of this accessible habitat for astrobiological research.

Microbial monitoring and microbial diversity in the EDEN-ISS greenhouse, a test facility for plant-cultivation in space

The limited storage space for consumable goods like food and medicine is one of the major factors currently limiting the duration and distance of crewed spaceflight missions. To overcome these limitations research into bio-regenerative life support systems (BLSS) is being conducted. BLSS utilize the regenerative abilities of plants and microorganisms to provide food, clean water, breathable air and potentially other goods like medicine. Before these technologies can be incorporated they need to be extensively tested and validated on Earth. TheEDEN-ISS project aimed to test plant cultivation technologies for BLSS in a space analogue environment. These technologies were tested in a greenhouse situated at the Neumayer III station in Antarctica for multiple years, to secure an isolated test environment. To ensure the continued operation of a BLSS, it is vital that plants remain healthy, which necessitates the monitoring of the greenhouse microbiome to ensure that pathogens are detected early and counter-measures can be engaged.During different campaigns, swab surface samples were taken from various locations in the greenhouse before/after cleaning and samples taken at regular intervals over an entire growing season. The bioburden of each sample was estimated via viable count and the isolates were identified via partial 16S rRNA gene sequencing. Additionally, 16S amplicon sequencing was performed on DNA extracted directly from the swab-samples to characterize the microbiome.The results revealed that the bioburden of the different sampling positions was not significantly reduced by the cleaning, indicating that the employed cleaning regime was unsuited in its current form to adequately lower the bioburden.Identification of the isolates as well as the full microbiome revealed mostly environmental genera. However, in both cases genera containing potential pathogens were identified. The two sets of sequencing data had little overlap and emphasized different aspects of the greenhouse microbiome, highlighting the advantages of using a combined approach to obtain a more complete picture of the microbiome composition.

From planetary safety to cultural heritage: an interdisciplinary exploration of microorganisms on inanimate surfaces

Interdisciplinary approaches at the intersection of microbiology, cultural heritage, material sciences, and biosafety broaden the frontiers of knowledge by offering enriched perspectives on microbial communities and their interactions with the objects and materials they inhabit. Along these lines, we have investigated the microbial communities present on cultural heritage objects, such as ancient medieval booksa housed at the Leipzig University Library, and those associated with the bioburden controls of spacecraft and cleanroom facilities of the European Space Agency (ESA)b mandated by planetary protection policies. Although these isolation sources might initially appear unrelated, both datasets share common taxa known for their capacity to survive under extreme conditions. These include endospore-forming genera Bacillus, Paenibacillus, Peribacillus, and Priestia, but also other genera including Micrococcus, Kocuria, and Staphylococcus. A current project moves beyond cataloguing efforts to employ targeted microbial cultivation combined with phylogenomic and functional analyses to investigate specific survival strategies of staphylococcal taxa. This work has broader implications, given the potential pathogenicity of the target genus. Samples were retrieved from 13th-century medieval manuscripts and from spaceflight hardware and assembly facilities at several ESA locations. Selected Staphylococcus epidermidis isolates were fully sequenced using a combination of long- and short-read sequencing technologies, followed by bioinformatic assembly. We obtained, twelve high-quality, closed S. epidermidis genomes from the medieval manuscripts and twenty-three from the ESA collection. Ongoing phylogenetic and functional analyses aim to elucidate evolutionary relationships and explore the mechanisms of persistence under extreme conditions. Our interdisciplinary and in-depth profiling of the ESA collection and cultural heritage isolates contributes not only to bioburden control strategies for space missions but also hold relevance for terrestrial facilities, such as hospitals and food production sites, where stringent contamination controls are critical, as well as for the preservation of cultural heritage.aFlocco et al. 2023. Touching the (almost) untouchable: a minimally invasive workflow [..] DOI: 10.3389/fmicb.2023.1197837.bThe ESA Microbial Collection at the DSMZ. www.dsmz.de/collection/catalogue/microorganisms/special-groups-of-organisms/esa-strains

FG Space microbiology

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