Mutagenesis in bacterial spores exposed to space and simulated martian conditions: data from the EXPOSE-E spaceflight experiment PROTECT

Susceptibility of extremophiles to far-UVC light for bioburden reduction in spacecraft assembly facilities

The prevention and reduction of microbial species entering and leaving Earth's biosphere is a critical aspect of planetary protection research. While various decontamination methods exist and are currently utilized for planetary protection purposes, the use of far-UVC light (200-230 nm) as a means for microbial reduction remains underexplored. Unlike conventional germicidal ultraviolet at 254 nm, which can pose a health risk to humans even with small exposure doses, far-UVC light poses minimal health hazard making it a suitable candidate for implementation in occupied areas of spacecraft assembly facilities. This study investigates the efficacy of far-UVC 222-nm light to inactivate bacteria using microbial species which are relevant to planetary protection either in vegetative cell or spore form. All the tested vegetative cells demonstrated susceptibility to 222-nm exposure, although susceptibility varied among the tested species. Notably, Deinococcus radiodurans, a species highly tolerant to extreme environmental conditions, exhibited the most resistance to far-UVC exposure with a dose of 112 mJ/cm2 required for a 1-log reduction in survival. While spore susceptibility was similar across the species tested, Bacillus pumilus spores were the most resistant of the tested spores when analyzed with a bi-exponential cell killing model (D90 of 6.8 mJ/cm2). Overall, these results demonstrate the efficacy of far-UVC light for reducing microbial bioburden to help ensure the success and safety of future space exploration missions.

Survival of microorganisms during two-year exposure in outer space near the ISS

Results of an experiment named "Test" on survival and variability of microorganisms in open space near the International Space Station are presented. It was found after two-years exposure, spore-forming bacteria of the species Bacillus subtilis, fungi of the species Aureobasidium pullulans and archaea of the species Methanosarcina mazei S-6T, deposited on cotton wool, are able to survive, and their numbers decreased equally, regardless of whether the microorganisms belong to different taxonomic groups. The main factors for the long-term survival could be the result of their dehydration and partial lyophilization in the vacuum of near-Earth space. For the first time, after being in outer space, cyst-like cells of the archaea strain M. mazei S-6T and a 14-day delay in their growth were detected when cultured on a nutrient medium compared to the ground-based control strain. In 30% of fungi species strains A. pullulans, isolated after a two-year stay in outer space, the resistance to γ-radiation increased compared to the control strain. It was found that the reaction to the action of various concentrations of hydrogen peroxide and 1% chlorine in the surviving strains of the fungus A. pullulans on the ISS is less pronounced than in the control strain.

COSPAR Sample Safety Assessment Framework (SSAF)

The Committee on Space Research (COSPAR) Sample Safety Assessment Framework (SSAF) has been developed by a COSPAR appointed Working Group. The objective of the sample safety assessment would be to evaluate whether samples returned from Mars could be harmful for Earth's systems (e.g., environment, biosphere, geochemical cycles). During the Working Group's deliberations, it became clear that a comprehensive assessment to predict the effects of introducing life in new environments or ecologies is difficult and practically impossible, even for terrestrial life and certainly more so for unknown extraterrestrial life. To manage expectations, the scope of the SSAF was adjusted to evaluate only whether the presence of martian life can be excluded in samples returned from Mars. If the presence of martian life cannot be excluded, a Hold & Critical Review must be established to evaluate the risk management measures and decide on the next steps. The SSAF starts from a positive hypothesis (there is martian life in the samples), which is complementary to the null-hypothesis (there is no martian life in the samples) typically used for science. Testing the positive hypothesis includes four elements: (1) Bayesian statistics, (2) subsampling strategy, (3) test sequence, and (4) decision criteria. The test sequence capability covers self-replicating and non-self-replicating biology and biologically active molecules. Most of the investigations associated with the SSAF would need to be carried out within biological containment. The SSAF is described in sufficient detail to support planning activities for a Sample Receiving Facility (SRF) and for preparing science announcements, while at the same time acknowledging that further work is required before a detailed Sample Safety Assessment Protocol (SSAP) can be developed. The three major open issues to be addressed to optimize and implement the SSAF are (1) setting a value for the level of assurance to effectively exclude the presence of martian life in the samples, (2) carrying out an analogue test program, and (3) acquiring relevant contamination knowledge from all Mars Sample Return (MSR) flight and ground elements. Although the SSAF was developed specifically for assessing samples from Mars in the context of the currently planned NASA-ESA MSR Campaign, this framework and the basic safety approach are applicable to any other Mars sample return mission concept, with minor adjustments in the execution part related to the specific nature of the samples to be returned. The SSAF is also considered a sound basis for other COSPAR Planetary Protection Category V, restricted Earth return missions beyond Mars. It is anticipated that the SSAF will be subject to future review by the various MSR stakeholders.

Absence of increased genomic variants in the cyanobacterium Chroococcidiopsis exposed to Mars-like conditions outside the space station

Despite the increasing interest in using microbial-based technologies to support human space exploration, many unknowns remain not only on bioprocesses but also on microbial survivability and genetic stability under non-Earth conditions. Here the desert cyanobacterium Chroococcidiopsis sp. CCMEE 029 was investigated for robustness of the repair capability of DNA lesions accumulated under Mars-like conditions (UV radiation and atmosphere) simulated in low Earth orbit using the EXPOSE-R2 facility installed outside the International Space Station. Genomic alterations were determined in a space-derivate of Chroococcidiopsis sp. CCMEE 029 obtained upon reactivation on Earth of the space-exposed cells. Comparative analysis of whole-genome sequences showed no increased variant numbers in the space-derivate compared to triplicates of the reference strain maintained on the ground. This result advanced cyanobacteria-based technologies to support human space exploration.

Environmental dependence of competitive fitness in rifampin-resistant rpoB mutants of Bacillus subtilis

RNA polymerase (RNAP) is a highly conserved macromolecular machine that contributes to the flow of genetic information from genotype to phenotype. In Bacillus subtilis , mutations in the rpoB gene encoding the β-subunit of RNAP have been shown to alter a number of global phenotypes including growth, utilization of unusual nutrient sources, sporulation, germination, and production of secondary metabolites. In addition, the spectrum of mutations in rpoB leading to rifampin resistance (Rif R ) can change dramatically depending upon the environment to which B. subtilis cells or spores are exposed. Rif R rpoB mutations have historically been associated with slower growth and reduced fitness; however, these assessments of fitness were conducted on limited collections of mutants in rich laboratory media that poorly reflect natural environments typically inhabited by B. subtilis . Using a novel, deep-sequencing approach in addition to traditional measurements of growth rate, lag time, and pairwise competitions, we demonstrated the competitive advantage of specific rpoB alleles differs depending on the growth environment in which they are determined.

IMPORTANCE

Microbial resistance to antibiotics is a growing threat to public health across the world. Historically, resistance to antibiotics has been associated with reduced fitness. A growing body of evidence indicates that resistance to rifampin, a frontline antibiotic used to treat mycobacterial and biofilm-associated infections, may increase fitness given an appropriate environment even in the absence of the selective antibiotic. Here we experimentally confirm this phenomenon by directly comparing the fitness of multiple rifampin-resistant mutants of Bacillus subtilis in rich LB medium and an asparagine minimal medium. Our research demonstrates that the fitness cost of rifampin resistance can vary greatly depending upon the environment. This has important implications for understanding how microbes develop antimicrobial resistance in the absence of antibiotic selection.

Mutation Analysis of the rpoB Gene in the Radiation-Resistant Bacterium Deinococcus radiodurans R1 Exposed to Space during the Tanpopo Experiment at the International Space Station

To investigate microbial viability and DNA damage, dried cell pellets of the radiation-resistant bacterium Deinococcus radiodurans were exposed to various space environmental conditions at the Exposure Facility of the International Space Station (ISS) as part of the Tanpopo mission. Mutation analysis was done by sequencing the rpoB gene encoding RNA polymerase β-subunit of the rifampicin-resistant mutants. Samples included bacteria exposed to the space environment with and without exposure to UV radiation as well as control samples held in the ISS cabin and at ground. The mutation sites of the rpoB gene obtained from the space-exposed and ISS/ground control samples were similar to the rpoB mutation sites previously reported in D. radiodurans. Most mutations were found at or near the rifampicin binding site in the RNA polymerase β-subunit. Mutation sites found in UV-exposed samples were mostly shared with non-exposed and ISS/ground control samples. These results suggest that most mutations found in our experiments were induced during procedures that were applied across all treatments: preparation, transfer from our laboratory to the ISS, return from the ISS, and storage before analysis. Some mutations may be enhanced by specific factors in the space experiments, but the mutations were also found in the spontaneous and control samples. Our experiment suggests that the dried cells of the microorganism D. radiodurans can travel without space-specific deterioration that may induce excess mutations relative to travel at Earth's surface. However, upon arrival at a recipient location, they must still be able to survive and repair the general damage induced during travel.

The Spectrum of Spontaneous Rifampin Resistance Mutations in the Bacillus subtilis rpoB Gene Depends on the Growth Environment

Results from previous investigations into spontaneous rifampin resistance (Rifr) mutations in the Bacillus subtilis rpoB gene suggested that the spectrum of mutations depends on the growth environment. However, these studies were limited by low sample numbers, allowing for the potential distortion of the data by the presence of "jackpot" mutations that may have arisen early in the growth of a population. Here, we addressed this issue by performing fluctuation analyses to assess both the rate and spectrum of Rifr mutations in two distinct media: LB, a complete laboratory medium, and SMMAsn, a minimal medium utilizing l-asparagine as the sole carbon source. We cultivated 60 separate populations under each growth condition and determined the mutation rate to Rifr to be slightly but significantly higher in LB cultures. We then sequenced the relevant regions of rpoB to map the spectrum of Rifr mutations under each growth condition. We found a distinct spectrum of mutations in each medium; LB cultures were dominated by the H482Y mutation (27/53 or 51%), whereas SMMAsn cultures were dominated by the S487L mutation (24/51 or 47%). Furthermore, we found through competition experiments that the relative fitness of the S487L mutant was significantly higher in SMMAsn than in LB medium. We therefore conclude that both the spectrum of Rifr mutations in the B. subtilis rpoB gene and the fitness of resulting mutants are influenced by the growth environment. IMPORTANCE The rpoB gene encodes the beta subunit of RNA polymerase, and mutations in rpoB are key determinants of resistance to the clinically important antibiotic rifampin. We show here that the spectrum of mutations in Bacillus subtilis rpoB depends on the medium in which the cells are cultivated. The results show that the growth environment not only plays a role in natural selection and fitness but also influences the probability of mutation at particular bases within the target gene.

Molecular Mechanisms of Microbial Survivability in Outer Space: A Systems Biology Approach

Since the dawn of space exploration, the survivability of terrestrial life in outer space conditions has attracted enormous attention. Space technology has enabled the development of advanced space exposure facilities to investigate in situ responses of microbial life to the stress conditions of space during interplanetary transfer. Significant progress has been made toward the understanding of the effects of space environmental factors, e.g., microgravity, vacuum and radiation, on microorganisms exposed to real and simulated space conditions. Of extreme importance is not only knowledge of survival potential of space-exposed microorganisms, but also the determination of mechanisms of survival and adaptation of predominant species to the extreme space environment, i.e., revealing the molecular machinery, which elicit microbial survivability and adaptation. Advanced technologies in -omics research have permitted genome-scale studies of molecular alterations of space-exposed microorganisms. A variety of reports show that microorganisms grown in the space environment exhibited global alterations in metabolic functions and gene expression at the transcriptional and translational levels. Proteomic, metabolomic and especially metabolic modeling approaches as essential instruments of space microbiology, synthetic biology and metabolic engineering are rather underrepresented. Here we summarized the molecular space-induced alterations of exposed microorganisms in terms of understanding the molecular mechanisms of microbial survival and adaptation to drastic outer space environment.

Freezing Tolerance of Thermophilic Bacterial Endospores in Marine Sediments

Dormant endospores of anaerobic, thermophilic bacteria found in cold marine sediments offer a useful model for studying microbial biogeography, dispersal, and survival. The dormant endospore phenotype confers resistance to unfavorable environmental conditions, allowing dispersal to be isolated and studied independently of other factors such as environmental selection. To study the resilience of thermospores to conditions relevant for survival in extreme cold conditions, their viability following different freezing treatments was tested. Marine sediment was frozen at either −80°C or −20°C for 10 days prior to pasteurization and incubation at +50°C for 21 days to assess thermospore viability. Sulfate reduction commenced at +50°C following both freezing pretreatments indicating persistence of thermophilic endospores of sulfate-reducing bacteria. The onset of sulfate reduction at +50°C was delayed in −80°C pretreated microcosms, which exhibited more variability between triplicates, compared to −20°C pretreated microcosms and parallel controls that were not frozen in advance. Microbial communities were evaluated by 16S rRNA gene amplicon sequencing, revealing an increase in the relative sequence abundance of thermophilic endospore-forming Firmicutes in all microcosms. Different freezing pretreatments (−80°C and −20°C) did not appreciably influence the shift in overall bacterial community composition that occurred during the +50°C incubations. Communities that had been frozen prior to +50°C incubation showed an increase in the relative sequence abundance of operational taxonomic units (OTUs) affiliated with the class Bacilli, relative to unfrozen controls. These results show that freezing impacts but does not obliterate thermospore populations and their ability to germinate and grow under appropriate conditions. Indeed the majority of the thermospore OTUs detected in this study (21 of 22) could be observed following one or both freezing treatments. These results are important for assessing thermospore viability in frozen samples and following cold exposure such as the very low temperatures that would be encountered during panspermia.

Single-cell analysis reveals individual spore responses to simulated space vacuum

Outer space is a challenging environment for all forms of life, and dormant spores of bacteria have been frequently used to study the survival of terrestrial life in a space journey. Previous work showed that outer space vacuum alone can kill bacterial spores. However, the responses and mechanisms of resistance of individual spores to space vacuum are unclear. Here, we examined spores’ molecular changes under simulated space vacuum (~10⁻⁵ Pa) using micro-Raman spectroscopy and found that this vacuum did not cause significant denaturation of spore protein. Then, live-cell microscopy was developed to investigate the temporal events during germination, outgrowth, and growth of individual Bacillus spores. The results showed that after exposure to simulated space vacuum for 10 days, viability of spores of two Bacillus species was reduced up to 35%, but all spores retained their large Ca²⁺-dipicolinic acid depot. Some of the killed spores did not germinate, and the remaining germinated but did not proceed to vegetative growth. The vacuum treatment slowed spore germination, and changed average times of all major germination events. In addition, viable vacuum-treated spores exhibited much greater sensitivity than untreated spores to dry heat and hyperosmotic stress. Among spores’ resistance mechanisms to high vacuum, DNA-protective α/β−type small acid-soluble proteins, and non-homologous end joining and base excision repair of DNA played the most important roles, especially against multiple cycles of vacuum treatment. Overall, these results give new insight into individual spore’s responses to space vacuum and provide new techniques for microorganism analysis at the single-cell level.

Probiotics into outer space: feasibility assessments of encapsulated freeze-dried probiotics during 1 month's storage on the International Space Station

Suppression of immune function during long spaceflights is an issue that needs to be overcome. The well-established probiotic Lactobacillus casei strain Shirota (LcS) could be a promising countermeasure, and we have launched a project to investigate the efficacy of its use on the International Space Station (ISS). As a first step, we developed a specialist probiotic product for space experiments, containing freeze-dried LcS in capsule form (Probiotics Package), and tested its stability through 1 month of storage on the ISS. The temperature inside the ISS ranged from 20.0 to 24.5 °C. The absorbed dose rate of the flight sample was 0.26 mGy/day and the dose equivalent rate was 0.52 mSv/day. The number of live LcS was 1.05 × 10¹¹ colony-forming units/g powder (49.5% of the initial value) 6 months after the start of the study; this value was comparable to those in the two ground controls. Profiles of randomly amplified polymorphic DNA, sequence variant frequency, carbohydrate fermentation, reactivity to LcS-specific antibody, and the cytokine-inducing ability of LcS in the flight sample did not differ from those of the ground controls. We can therefore maintain the viability and basic probiotic properties of LcS stored as a Probiotics Package on the ISS.

BIOMEX Experiment: Ultrastructural Alterations, Molecular Damage and Survival of the Fungus Cryomyces antarcticus after the Experiment Verification Tests

The search for traces of extinct or extant life in extraterrestrial environments is one of the main goals for astrobiologists; due to their ability to withstand stress producing conditions, extremophiles are perfect candidates for astrobiological studies. The BIOMEX project aims to test the ability of biomolecules and cell components to preserve their stability under space and Mars-like conditions, while at the same time investigating the survival capability of microorganisms. The experiment has been launched into space and is being exposed on the EXPOSE-R2 payload, outside of the International Space Station (ISS) over a time-span of 1.5 years. Along with a number of other extremophilic microorganisms, the Antarctic cryptoendolithic black fungus Cryomyces antarcticus CCFEE 515 has been included in the experiment. Before launch, dried colonies grown on Lunar and Martian regolith analogues were exposed to vacuum, irradiation and temperature cycles in ground based experiments (EVT1 and EVT2). Cultural and molecular tests revealed that the fungus survived on rock analogues under space and simulated Martian conditions, showing only slight ultra-structural and molecular damage.

The Janus face of iron on anoxic worlds: iron oxides are both protective and destructive to life on the early Earth and present-day Mars

The surface of the early Earth was probably subjected to a higher flux of ultraviolet (UV) radiation than today. UV radiation is known to severely damage DNA and other key molecules of life. Using a liquid culture and a rock analogue system, we investigated the interplay of protective and deleterious effects of iron oxides under UV radiation on the viability of the model organism, Bacillus subtilis. In the presence of hydrogen peroxide, there exists a fine balance between iron oxide's protective effects against this radiation and its deleterious effects caused by Photo-Fenton reactions. The maximum damage was caused by a concentration of hematite of ∼1 mg/mL. Concentrations above this confer increasing protection by physical blockage of the UV radiation, concentrations below this cause less effective UV radiation blockage, but also a correspondingly less effective Photo-Fenton reaction, providing an overall advantage. These results show that on anoxic worlds, surface habitability under a high UV flux leaves life precariously poised between the beneficial and deleterious effects of iron oxides. These results have relevance to the Archean Earth, but also the habitability of the Martian surface, where high levels of UV radiation in combination with iron oxides and hydrogen peroxide can be found.

Stratosphere Conditions Inactivate Bacterial Endospores from a Mars Spacecraft Assembly Facility

Every spacecraft sent to Mars is allowed to land viable microbial bioburden, including hardy endospore-forming bacteria resistant to environmental extremes. Earth's stratosphere is severely cold, dry, irradiated, and oligotrophic; it can be used as a stand-in location for predicting how stowaway microbes might respond to the martian surface. We launched E-MIST, a high-altitude NASA balloon payload on 10 October 2015 carrying known quantities of viable Bacillus pumilus SAFR-032 (4.07 × 10⁷ spores per sample), a radiation-tolerant strain collected from a spacecraft assembly facility. The payload spent 8 h at ∼31 km above sea level, exposing bacterial spores to the stratosphere. We found that within 120 and 240 min, spore viability was significantly reduced by 2 and 4 orders of magnitude, respectively. By 480 min, <0.001% of spores carried to the stratosphere remained viable. Our balloon flight results predict that most terrestrial bacteria would be inactivated within the first sol on Mars if contaminated spacecraft surfaces receive direct sunlight. Unfortunately, an instrument malfunction prevented the acquisition of UV light measurements during our balloon mission. To make up for the absence of radiometer data, we calculated a stratosphere UV model and conducted ground tests with a 271.1 nm UVC light source (0.5 W/m²), observing a similarly rapid inactivation rate when using a lower number of contaminants (640 spores per sample). The starting concentration of spores and microconfiguration on hardware surfaces appeared to influence survivability outcomes in both experiments. With the relatively few spores that survived the stratosphere, we performed a resequencing analysis and identified three single nucleotide polymorphisms compared to unexposed controls. It is therefore plausible that bacteria enduring radiation-rich environments (e.g., Earth's upper atmosphere, interplanetary space, or the surface of Mars) may be pushed in evolutionarily consequential directions. Key Words: Planetary protection-Stratosphere-Balloon-Mars analog environment-E-MIST payload-Bacillus pumilus SAFR-032. Astrobiology 17, 337-350.

Simulated Space Radiation: Impact of Four Different Types of High-Dose Ionizing Radiation on the Lichen Xanthoria elegans

This study addresses the viability of the lichen Xanthoria elegans after high-dose ionizing irradiation in the frame of the STARLIFE campaign. The first set of experiments was intended to resemble several types of galactic cosmic radiation (GCR) as present beyond the magnetic shield of Earth. In the second set of experiments, γ radiation up to 113 kGy was applied to test the limit of lichen resistance to ionizing radiation. Entire thalli of Xanthoria elegans were irradiated in the anhydrobiotic state. After STARLIFE 1, the metabolic activity of both symbionts was quantified by live/dead staining with confocal laser scanning microscopy. The photosynthetic activity was measured after the respective irradiation to assess the ability of the symbiotic green algae to restore photosynthesis after irradiation. The STARLIFE campaign complements the results of the LIFE experiments at the EXPOSE-E facility on the International Space Station by testing the model organism Xanthoria elegans on its resistance to hazardous radiation that might be accumulated during long-term space exposure. In addition, the photosynthetic activity of metabolically active lichen was investigated after X-ray irradiation up to 100 Gy (3.3 Gy/min). Since previous astrobiological experiments were mostly performed with anhydrobiotic lichen, these experiments will broaden our knowledge on the correlation of physiological state and astrobiological stressors. Key Words: Astrobiology-Extremotolerance-Gamma rays-Ionizing radiation-Lichens-Viability. Astrobiology 17, 136-144.

Venturing into new realms? Microorganisms in space

One of the biggest challenges of science is the determination of whether extraterrestrial life exists. Although potential habitable areas might be available for complex life, it is more likely that microbial life could exist in space. Many extremotolerant and extremophilic microbes have been found to be able to withstand numerous, combined environmental factors, such as high or low temperatures and pressures, high-salt conditions, high doses of radiation, desiccation or nutrient limitations. They may even survive the transit from one planet to another. Terrestrial Mars-analogue sites are one focus of researchers, in order to understand the microbial diversity in preparation for upcoming space missions aimed at the detection of life. However, such missions could also pose a risk with respect to contamination of the extraterrestrial environment by accidentally transferred terrestrial microorganisms. Closer to the Earth, the International Space Station is the most enclosed habitat, where humans work and live-and with them numerous microorganisms. It is still unknown how microbes adapt to this environment, possibly even creating a risk for the crew. Information on the microbiology of the ISS will have an impact on the planning and implementation of long-term human spaceflights in order to ensure a safe, stable and balanced microbiome on board.

Isolation of Radiation-Resistant Bacteria from Mars Analog Antarctic Dry Valleys by Preselection, and the Correlation between Radiation and Desiccation Resistance

Extreme radiation-resistant microorganisms can survive doses of ionizing radiation far greater than are present in the natural environment. Radiation resistance is believed to be an incidental adaptation to desiccation resistance, as both hazards cause similar cellular damage. Desert soils are, therefore, promising targets to prospect for new radiation-resistant strains. This is the first study to isolate radiation-resistant microbes by using gamma-ray exposure preselection from the extreme cold desert of the Antarctic Dry Valleys (a martian surface analogue). Halomonads, identified by 16S rRNA gene sequencing, were the most numerous survivors of the highest irradiation exposures. They were studied here for the first time for both their desiccation and irradiation survival characteristics. In addition, the association between desiccation and radiation resistance has not been investigated quantitatively before for a broad diversity of microorganisms. Thus, a meta-analysis of scientific literature was conducted to gather a larger data set. A strong correlation was found between desiccation and radiation resistance, indicating that an increase in the desiccation resistance of 5 days corresponds to an increase in the room-temperature irradiation survival of 1 kGy. Irradiation at -79°C (representative of average martian surface temperatures) increases the microbial radiation resistance 9-fold. Consequently, the survival of the cold-, desiccation-, and radiation-resistant organisms isolated here has implications for the potential habitability of dormant or cryopreserved life on Mars.

KEY WORDS

Extremophiles-Halomonas sp.-Antarctica-Mars-Ionizing radiation-Cosmic rays.

Functional activity of plasmid DNA after entry into the atmosphere of earth investigated by a new biomarker stability assay for ballistic spaceflight experiments

Sounding rockets represent an excellent platform for testing the influence of space conditions during the passage of Earth's atmosphere and re-entry on biological, physical and chemical experiments for astrobiological purposes. We designed a robust functionality biomarker assay to analyze the biological effects of suborbital spaceflights prevailing during ballistic rocket flights. During the TEXUS-49 rocket mission in March 2011, artificial plasmid DNA carrying a fluorescent marker (enhanced green fluorescent protein: EGFP) and an antibiotic resistance cassette (kanamycin/neomycin) was attached on different positions of rocket exterior; (i) circular every 90 degree on the outer surface concentrical of the payload, (ii) in the grooves of screw heads located in between the surface application sites, and (iii) on the surface of the bottom side of the payload. Temperature measurements showed two major peaks at 118 and 130°C during the 780 seconds lasting flight on the inside of the recovery module, while outer gas temperatures of more than 1000°C were estimated on the sample application locations. Directly after retrieval and return transport of the payload, the plasmid DNA samples were recovered. Subsequent analyses showed that DNA could be recovered from all application sites with a maximum of 53% in the grooves of the screw heads. We could further show that up to 35% of DNA retained its full biological function, i.e., mediating antibiotic resistance in bacteria and fluorescent marker expression in eukariotic cells. These experiments show that our plasmid DNA biomarker assay is suitable to characterize the environmental conditions affecting DNA during an atmospheric transit and the re-entry and constitute the first report of the stability of DNA during hypervelocity atmospheric transit indicating that sounding rocket flights can be used to model the high-speed atmospheric entry of organics-laden artificial meteorites.

Changes in immune cell signalling, apoptosis and stress response functions in mice returned from the BION-M1 mission in space

To explore the effect of the spaceflight environment on immunity in animals, C57/BL6 mice flown on a 30-day space high-orbit satellite mission (BION-M1) were analyzed. Cytokine response in mice was measured in tandem with the following parameters: the synthesis of inducible forms of the heat shock proteins HSP72 and HSP90α; activity of the NF-κB, IFR3, and SAPK/JNK signalling pathways; and TLR4 expression. In addition, apoptosis in the thymus was measured by caspase-3 and ph-p53/p53 ratio testing. In response to flight environment exposure, mice had a reduction in spleen and thymus masses and decreased splenic and thymic lymphocyte counts. Plasma concentration of IL-6 and IFN-γ but not TNF-α was decreased in C57BL6 mice. The NF-κB activity in splenic lymphocytes through the canonical pathway involving IκB degradation was significantly increased at 12h after landing. One week after landing, however, the activity of NF-κB was markedly decreased below even the control values. Non-canonical NF-κB activity increased during the whole observation period. The activities of SAPK/JNK and IRF-3 were invariable at 12h but significantly increased 7 days after landing. The expression of Hsp72 and Hsp90α was somewhat increased 12h (Hsp72) and 7 days (Hsp90α). TLR4 expression in splenic cells was significantly increased only at 12h, returning to normal 7 days after landing. To assess the apoptosis in thymus lymphocytes, caspase-3 and levels of p53 protein along with its phosphorylated form were measured in thymic lymphocytes. The results indicated that the high-orbit spaceflight environment caused an increase in the level of p53 but more notably in the activated, phosphorylated form of the p53 protein. The calculated ratio of the active to inactive forms of the protein (ph-53/p53) 12h after landing increased by more than twofold, indicating the apparent induction of apoptosis in thymus cells. Interestingly, 7 days after the landing, this ratio was not restored, but rather increased: the specified ratio was four times higher compared to the ground-based control. Measurements of caspase-3 in thymic cells indicated more expressive increase in apoptosis. Taken together, the results of the present study indicate that spaceflight induces an imbalance in the immunity of mice, showing variation in signalling, apoptosis and stress response that are not restored by 7 days after landing. These changes are distinguished from classic stress-related alterations usually caused by conventional stressors.

Comparative genomic analysis of Klebsiella pneumonia (LCT-KP214) and a mutant strain (LCT-KP289) obtained after spaceflight

Background

With the development of space science, it is important to analyze the relationship between the space environment and genome variations that might cause phenotypic changes in microbes. Klebsiella pneumoniae is commonly found on the human body and is resistant to multiple drugs. To study space-environment-induced genome variations and drug resistance changes, K. pneumoniae was carried into outer space by the Shenzhou VIII spacecraft.

Results

The K. pneumoniae strain LCT-KP289 was selected after spaceflight based on its phenotypic differences compared to the ground-control strain. Analysis of genomic structural variations revealed one inversion, 25 deletions, fifty-nine insertions, two translocations and six translocations with inversions. In addition, 155 and 400 unique genes were observed in LCT-KP214 and LCT-KP289, respectively, including the gene encoding dihydroxyacetone kinase, which generates the ATP and NADH required for microbial growth. Furthermore, a large number of mutant genes were related to transport and metabolism. Phylogenetic analysis revealed that most genes in these two strains had a dN/dS value greater than 1, indicating that the strain diversity increased after spaceflight. Analysis of drug-resistance phenotypes revealed that the K. pneumoniae strain LCT-KP289 was resistant to sulfamethoxazole, whereas the control strain, LCT-KP214, was not; both strains were resistant to benzylpenicillin, ampicillin, lincomycin, vancomycin, chloramphenicol and streptomycin. The sulfamethoxazole resistance may be associated with sequences in Scaffold7 in LCT-KP289, which were not observed in LCT-K214; this scaffold contained the gene sul1. In the strain LCT-KP289, we also observed a drug-resistance integron containing emrE (confers multidrug resistance) and ant (confers resistance to spectinomycin, streptomycin, tobramycin, kanamycin, sisomicin, dibekacin, and gentamicin). The gene ampC (confers resistance to penicillin, cephalosporin-ii and cephalosporin-i) was present near the integron. In addition, 30 and 26 drug-resistance genes were observed in LCT-KP289 and LCT-KP214, respectively.

Conclusions

Comparison of a K. pneumoniae strain obtained after spaceflight with the ground-control strain revealed genome variations and phenotypic changes and elucidated the genomic basis of the acquired drug resistance. These data pave the way for future studies on the effects of spaceflight.

Microbes in the upper atmosphere and unique opportunities for astrobiology research

Microbial taxa from every major biological lineage have been detected in Earth's upper atmosphere. The goal of this review is to communicate (1) relevant astrobiology questions that can be addressed with upper atmosphere microbiology studies and (2) available sampling methods for collecting microbes at extreme altitudes. Precipitation, mountain stations, airplanes, balloons, rockets, and satellites are all feasible routes for conducting aerobiology research. However, more efficient air samplers are needed, and contamination is also a pervasive problem in the field. Measuring microbial signatures without false positives in the upper atmosphere might contribute to sterilization and bioburden reduction methods for proposed astrobiology missions. Intriguingly, environmental conditions in the upper atmosphere resemble the surface conditions of Mars (extreme cold, hypobaria, desiccation, and irradiation). Whether terrestrial microbes are active in the upper atmosphere is an area of intense research interest. If, in fact, microbial metabolism, growth, or replication is achievable independent of Earth's surface, then the search for habitable zones on other worlds should be broadened to include atmospheres (e.g., the high-altitude clouds of Venus). Furthermore, viable cells in the heavily irradiated upper atmosphere of Earth could help identify microbial genes or enzymes that bestow radiation resistance. Compelling astrobiology questions on the origin of life (if the atmosphere synthesized organic aerosols), evolution (if airborne transport influenced microbial mutation rates and speciation), and panspermia (outbound or inbound) are also testable in Earth's upper atmosphere.

Biofilm and planktonic lifestyles differently support the resistance of the desert cyanobacterium Chroococcidiopsis under space and Martian simulations

When Chroococcidiopsis sp. strain CCMEE 057 from the Sinai Desert and strain CCMEE 029 from the Negev Desert were exposed to space and Martian simulations in the dried status as biofilms or multilayered planktonic samples, the biofilms exhibited an enhanced rate of survival. Compared to strain CCMEE 029, biofilms of strain CCME 057 better tolerated UV polychromatic radiation (5 × 10(5) kJ/m(2) attenuated with a 0.1% neutral density filter) combined with space vacuum or Martian atmosphere of 780 Pa. CCMEE 029, on the other hand, failed to survive UV polychromatic doses higher than 1.5 × 10(3) kJ/m(2). The induced damage to genomic DNA, plasma membranes and photosynthetic apparatus was quantified and visualized by means of PCR-based assays and CLSM imaging. Planktonic samples of both strains accumulated a higher amount of damage than did the biofilms after exposure to each simulation; CLSM imaging showed that photosynthetic pigment bleaching, DNA fragmentation and damaged plasma membranes occurred in the top 3-4 cell layers of both biofilms and of multilayered planktonic samples. Differences in the EPS composition were revealed by molecular probe staining as contributing to the enhanced endurance of biofilms compared to that of planktonic samples. Our results suggest that compared to strain CCMEE 029, biofilms of strain CCMEE 057 might better tolerate 1 year's exposure in space during the next EXPOSE-R2 mission.

Changes in mouse thymus and spleen after return from the STS-135 mission in space

Our previous results with flight (FLT) mice showed abnormalities in thymuses and spleens that have potential to compromise immune defense mechanisms. In this study, the organs were further evaluated in C57BL/6 mice after Space Shuttle Atlantis returned from a 13-day mission. Thymuses and spleens were harvested from FLT mice and ground controls housed in similar animal enclosure modules (AEM). Organ and body mass, DNA fragmentation and expression of genes related to T cells and cancer were determined. Although significance was not obtained for thymus mass, DNA fragmentation was greater in the FLT group (P<0.01). Spleen mass alone and relative to body mass was significantly decreased in FLT mice (P<0.05). In FLT thymuses, 6/84 T cell-related genes were affected versus the AEM control group (P<0.05; up: IL10, Il18bp, Il18r1, Spp1; down: Ccl7, IL6); 15/84 cancer-related genes had altered expression (P<0.05; up: Casp8, FGFR2, Figf, Hgf, IGF1, Itga4, Ncam1, Pdgfa, Pik3r1, Serpinb2, Sykb; down: Cdc25a, E2F1, Mmp9, Myc). In the spleen, 8/84 cancer-related genes were affected in FLT mice compared to AEM controls (P<0.05; up: Cdkn2a; down: Birc5, Casp8, Ctnnb1, Map2k1, Mdm2, NFkB1, Pdgfa). Pathway analysis (apoptosis signaling and checkpoint regulation) was used to map relationships among the cancer–related genes. The results showed that a relatively short mission in space had a significant impact on both organs. The findings also indicate that immune system aberrations due to stressors associated with space travel should be included when estimating risk for pathologies such as cancer and infection and in designing appropriate countermeasures. Although this was the historic last flight of NASA’s Space Shuttle Program, exploration of space will undoubtedly continue.

Utilization of low-pressure plasma to inactivate bacterial spores on stainless steel screws

A special focus area of planetary protection is the monitoring, control, and reduction of microbial contaminations that are detected on spacecraft components and hardware during and after assembly. In this study, wild-type spores of Bacillus pumilus SAFR-032 (a persistent spacecraft assembly facility isolate) and the laboratory model organism B. subtilis 168 were used to study the effects of low-pressure plasma, with hydrogen alone and in combination with oxygen and evaporated hydrogen peroxide as a process gas, on spore survival, which was determined by a colony formation assay. Spores of B. pumilus SAFR-032 and B. subtilis 168 were deposited with an aseptic technique onto the surface of stainless steel screws to simulate a spore-contaminated spacecraft hardware component, and were subsequently exposed to different plasmas and hydrogen peroxide conditions in a very high frequency capacitively coupled plasma reactor (VHF-CCP) to reduce the spore burden. Spores of the spacecraft isolate B. pumilus SAFR-032 were significantly more resistant to plasma treatment than spores of B. subtilis 168. The use of low-pressure plasma with an additional treatment of evaporated hydrogen peroxide also led to an enhanced spore inactivation that surpassed either single treatment when applied alone, which indicates the potential application of this method as a fast and suitable way to reduce spore-contaminated spacecraft hardware components for planetary protection purposes.

R3DE: Radiation Risk Radiometer-Dosimeter on the International Space Station--optical radiation data recorded during 18 months of EXPOSE-E exposure to open space

Radiation Risk Radiometer-Dosimeter E (R3DE) served as a device for measuring ionizing and non-ionizing radiation as well as cosmic radiation reaching biological samples located on the EXPOSE platform EXPOSE-E. The duration of the mission was almost 1.5 years (2008-2009). With four channels, R3DE detected the wavelength ranges of photosynthetically active radiation (PAR, 400-700 nm), UVA (315-400 nm), UVB (280-315 nm), and UVC (<280 nm). In addition, the temperature was recorded. Cosmic ionizing radiation was assessed with a 256-channel spectrometer dosimeter (see separate report in this issue). The light and UV sensors of the device were calibrated with spectral measurement data obtained by the Solar Radiation and Climate Experiment (SORCE) satellite as standard. The data were corrected with respect to the cosine error of the diodes. Measurement frequency was 0.1 Hz. Due to errors in data transmission or temporary termination of EXPOSE power, not all data could be acquired. Radiation was not constant during the mission. At regular intervals of about 2 months, low or almost no radiation was encountered. The radiation dose during the mission was 1823.98 MJ m(-2) for PAR, 269.03 MJ m(-2) for UVA, 45.73 MJ m(-2) for UVB, or 18.28 MJ m(-2) for UVC. Registered sunshine duration during the mission was about 152 days (about 27% of mission time).The surface of EXPOSE was most likely turned away from the Sun for considerably longer. R3DE played a crucial role on EXPOSE-EuTEF (EuTEF, European Technology Exposure Facility), because evaluation of the astrobiology experiments depended on reliability of the data collected by the device. Observed effects in the samples were weighted by radiation doses measured by R3DE.

Survival of spores of the UV-resistant Bacillus subtilis strain MW01 after exposure to low-earth orbit and simulated martian conditions: data from the space experiment ADAPT on EXPOSE-E

In the space experiment "Molecular adaptation strategies of microorganisms to different space and planetary UV climate conditions" (ADAPT), bacterial endospores of the highly UV-resistant Bacillus subtilis strain MW01 were exposed to low-Earth orbit (LEO) and simulated martian surface conditions for 559 days on board the European Space Agency's exposure facility EXPOSE-E, mounted outside the International Space Station. The survival of B. subtilis MW01 spores from both assays (LEO and simulated martian conditions) was determined by a colony-formation assay after retrieval. It was clearly shown that solar extraterrestrial UV radiation (λ≥110 nm) as well as the martian UV spectrum (λ≥200 nm) was the most deleterious factor applied; in some samples only a few spore survivors were recovered from B. subtilis MW01 spores exposed in monolayers. However, if shielded from solar irradiation, about 8% of MW01 spores survived in LEO conditions, and 100% survived in simulated martian conditions, compared to the laboratory controls. The results demonstrate the effect of shielding against the high inactivation potential of extraterrestrial solar UV radiation, which limits the chances of survival of even the highly UV-resistant strain of B. subtilis MW01 in the harsh environments of outer space and the martian surface.

EXPOSE-E: an ESA astrobiology mission 1.5 years in space

The multi-user facility EXPOSE-E was designed by the European Space Agency to enable astrobiology research in space (low-Earth orbit). On 7 February 2008, EXPOSE-E was carried to the International Space Station (ISS) on the European Technology Exposure Facility (EuTEF) platform in the cargo bay of Space Shuttle STS-122 Atlantis. The facility was installed at the starboard cone of the Columbus module by extravehicular activity, where it remained in space for 1.5 years. EXPOSE-E was returned to Earth with STS-128 Discovery on 12 September 2009 for subsequent sample analysis. EXPOSE-E provided accommodation in three exposure trays for a variety of astrobiological test samples that were exposed to selected space conditions: either to space vacuum, solar electromagnetic radiation at >110 nm and cosmic radiation (trays 1 and 3) or to simulated martian surface conditions (tray 2). Data on UV radiation, cosmic radiation, and temperature were measured every 10 s and downlinked by telemetry. A parallel mission ground reference (MGR) experiment was performed on ground with a parallel set of hardware and samples under simulated space conditions. EXPOSE-E performed a successful 1.5-year mission in space.

Resistance of bacterial endospores to outer space for planetary protection purposes--experiment PROTECT of the EXPOSE-E mission

Spore-forming bacteria are of particular concern in the context of planetary protection because their tough endospores may withstand certain sterilization procedures as well as the harsh environments of outer space or planetary surfaces. To test their hardiness on a hypothetical mission to Mars, spores of Bacillus subtilis 168 and Bacillus pumilus SAFR-032 were exposed for 1.5 years to selected parameters of space in the experiment PROTECT during the EXPOSE-E mission on board the International Space Station. Mounted as dry layers on spacecraft-qualified aluminum coupons, the "trip to Mars" spores experienced space vacuum, cosmic and extraterrestrial solar radiation, and temperature fluctuations, whereas the "stay on Mars" spores were subjected to a simulated martian environment that included atmospheric pressure and composition, and UV and cosmic radiation. The survival of spores from both assays was determined after retrieval. It was clearly shown that solar extraterrestrial UV radiation (λ≥110 nm) as well as the martian UV spectrum (λ≥200 nm) was the most deleterious factor applied; in some samples only a few survivors were recovered from spores exposed in monolayers. Spores in multilayers survived better by several orders of magnitude. All other environmental parameters encountered by the "trip to Mars" or "stay on Mars" spores did little harm to the spores, which showed about 50% survival or more. The data demonstrate the high chance of survival of spores on a Mars mission, if protected against solar irradiation. These results will have implications for planetary protection considerations.

Transcriptomic responses of germinating Bacillus subtilis spores exposed to 1.5 years of space and simulated martian conditions on the EXPOSE-E experiment PROTECT

Because of their ubiquity and resistance to spacecraft decontamination, bacterial spores are considered likely potential forward contaminants on robotic missions to Mars. Thus, it is important to understand their global responses to long-term exposure to space or martian environments. As part of the PROTECT experiment, spores of B. subtilis 168 were exposed to real space conditions and to simulated martian conditions for 559 days in low-Earth orbit mounted on the EXPOSE-E exposure platform outside the European Columbus module on the International Space Station. Upon return, spores were germinated, total RNA extracted, fluorescently labeled, and used to probe a custom Bacillus subtilis microarray to identify genes preferentially activated or repressed relative to ground control spores. Increased transcript levels were detected for a number of stress-related regulons responding to DNA damage (SOS response, SPβ prophage induction), protein damage (CtsR/Clp system), oxidative stress (PerR regulon), and cell envelope stress (SigV regulon). Spores exposed to space demonstrated a much broader and more severe stress response than spores exposed to simulated martian conditions. The results are discussed in the context of planetary protection for a hypothetical journey of potential forward contaminant spores from Earth to Mars and their subsequent residence on Mars.