Biological Life Support Systems Research Articles

Transcriptional response of Arabidopsis thaliana's root-tip to spaceflight.

Plants are expected to play a critical role in the biological life support systems of crewed spaceflight missions, including in the context of upcoming missions targeting the Moon and Mars. Therefore, understanding the response of plants to spaceflight is essential for improving the selection and engineering of plants and spaceflight conditions. In particular, understanding the root-tip's response to spaceflight is of importance as it is the center of orchestrating the development of the root, the primary organ for the absorption of nutrients and anchorage. GLDS-120 is a pioneering study by Paul et al. that used transcriptomics to evaluate the spaceflight response of the root-tip of the model plant Arabidopsis thaliana in dark and light through separate analyses of three genotype groups (Wassilewskija, Columbia-0, and Columbia-0 PhyD) and comparison of genotype responses. Here, we provide a complementary analysis of this dataset through a combined analysis of all samples while controlling for the genotypes in a paired analysis. We identified a robust transcriptional response to spaceflight with 622 DEGs in light and 200 DEGs in dark conditions. Gene enrichment analysis identified 37 and 13 significantly enriched terms from biological processes in light and dark conditions, respectively. Prominent enrichment for hypoxia-related terms in both conditions suggests hypoxia is a key stressor for root development during spaceflight. Additional enriched terms in light conditions include the circadian cycle, light response, and terms for the metabolism of flavonoid and indole-containing compounds. These results further our understanding of plants' responses to the spaceflight environment.

Cyanobacteria and Algal-Based Biological Life Support System (BLSS) and Planetary Surface Atmospheric Revitalizing Bioreactor Brief Concept Review.

Exploring austere environments required a reimagining of resource acquisition and utilization. Cyanobacterial in situ resources utilization (ISRU) and biological life support system (BLSS) bioreactors have been proposed to allow crewed space missions to extend beyond the temporal boundaries that current vehicle mass capacities allow. Many cyanobacteria and other microscopic organisms evolved during a period of Earth's history that was marked by very harsh conditions, requiring robust biochemical systems to ensure survival. Some species work wonderfully in a bioweathering capacity (siderophilic), and others are widely used for their nutritional power (non-siderophilic). Playing to each of their strengths and having them grow and feed off of each other is the basis for the proposed idea for a series of three bioreactors, starting from regolith processing and proceeding to nutritional products, gaseous liberation, and biofuel production. In this paper, we discuss what that three reactor system will look like, with the main emphasis on the nutritional stage.

ИССЛЕДОВАНИЯ СИСТЕМ ЖИЗНЕОБЕСПЕЧЕНИЯ НА ОСНОВЕ БИОГЕННЫХ МЕХАНИЗМОВ В ИНСТИТУТЕ МЕДИКО-БИОЛОГИЧЕСКИХ ПРОБЛЕМ РАН

The paper reviews researches conducted at RF SSC – IBMP/RAS with the goal to design a biological life support system (BLSS) for humans. Models of the human-unicellular algae-mineralization BLSS are proposed. Consideration is given to potential components for space BLSS (inferior and higher autotrophic organisms, heterotrophic organisms), biogenic mechanisms that can be used to regenerate human environment, and open issues associated with integration of the biogenic mechanisms in space crew life support systems. It would not be an overstatement to say that researches related to the BLSS development encompass all life sciences, and many other disciplines. In view of the ambition to explore remote space, the idea of BLSS will once again be in the forefront. Without this system the human will not be able to break away from Earth. Activities in this area are being continued and results of investigations contribute to overcoming the existing challenges with preparation for the future.

Sustaining a Mars Colony through Integration of Single-Cell Oil in Biological Life Support Systems

Abstract As humanity sets its sights on establishing a sustainable and prosperous colony on Mars, the main challenges to be overcome are ensuring a reliable and nutritious food supply for settlers, feedstock for 3D printing, fuel and pharmaceuticals. While various solutions for production of essential products on Mars have been proposed, there is growing interest in the use of microorganisms as the main production units. This scientific review article proposes a novel concept of using single cell oil (SCO) as a versatile feedstock for various applications in a bioregenerative life support system (BLSS) for space missions. The authors suggest using outputs from autotrophic systems, such as cyanobacteria biomass and oxygen, to cultivate SCO-producing microorganisms from the class Labyrinthulomycetes. The produced SCO can be used for food, fuel, 3D printing materials, and pharmaceuticals. This approach can potentially reduce the importance of carbohydrates in space foods, offering various benefits, including a reduction in food weight, simpler, lightweight, more compact bioreactors, launch cost reduction, potentially improved mental and cognitive performance, and reduced fatigue for the crew. The authors also suggest using SCO as the feedstock for the production of 3D printable filaments and resins and as a supplementary fuel source for space colonies. While the concept is hypothetical, the theoretical foundation is solid, and this approach could potentially become an important element required for the establishment of a successful Mars colony.

Euglena, a Gravitactic Flagellate of Multiple Usages.

Human exploration of space and other celestial bodies bears a multitude of challenges. The Earth-bound supply of material and food is restricted, and in situ resource utilisation (ISRU) is a prerequisite. Excellent candidates for delivering several services are unicellular algae, such as the space-approved flagellate Euglena gracilis. This review summarizes the main characteristics of this unicellular organism. Euglena has been exposed on various platforms that alter the impact of gravity to analyse its corresponding gravity-dependent physiological and molecular genetic responses. The sensory transduction chain of gravitaxis in E. gracilis has been identified. The molecular gravi-(mechano-)receptors are mechanosensory calcium channels (TRP channels). The inward gated calcium binds specifically to one of several calmodulins (CaM.2), which, in turn, activates an adenylyl cyclase. This enzyme uses ATP to produce cAMP, which induces protein kinase A, followed by the phosphorylation of a motor protein in the flagellum, initiating a course correction, and, finally, resulting in gravitaxis. During long space missions, a considerable amount of food, oxygen, and water has to be carried, and the exhaled carbon dioxide has to be removed. In this context, E. gracilis is an excellent candidate for biological life support systems, since it produces oxygen by photosynthesis, takes up carbon dioxide, and is even edible. Various species and mutants of Euglena are utilized as a producer of commercial food items, as well as a source of medicines, as it produces a number of vitamins, contains numerous trace elements, and synthesizes dietary proteins, lipids, and the reserve molecule paramylon. Euglena has anti-inflammatory, -oxidant, and -obesity properties.

Water recycle system in an artificial closed ecosystem – Lunar Palace 1: Treatment performance and microbial evolution

Water recycle systems have important implications to realize material circulation in biological regeneration life support systems, which is of significance for long-term space missions and future planetary base. Based on membrane biological activated carbon reactor (MBAR) technologies, the ‘Lunar Palace 365’ experiment established various treatment processes for condensate wastewater, domestic wastewater, urine, and used nutrient solutions. The 370-day operation data showed the CODMn index of purified condensate wastewater decreased to 0.74 ± 0.15 mg/L, which met the standards for drinking water quality. The average removal rate of organic contaminants in domestic wastewater by the MBAR was 85.7% ± 10.2%, and this MBAR also had a stable nitrification performance with effluent NO3−-N concentrations fluctuating from 145.57 mg/L to 328.59 mg/L. Moreover, the purification of urine achieved the conversion of urea-N to NH4+-N and thus the partial recovery of nitrogen. 16S rDNA sequencing results revealed the evolution of microbial diversity and composition during the long-term operation. Meiothermus, Rhodanobacter, and Ochrobactrum were the dominant microorganisms in various MBARs.

Optimized crop growth area composition for long duration spaceflight

This paper presents an optimized composition of crop growth areas for biological life support systems with respect to nutrition and equivalent system mass. For this purpose, crop growth area compositions from literature are compared with compositions derived from an optimization algorithm. The optimization algorithm uses literature data for crop growth rates and crop nutrient content to minimize the required crop growth area required to supply all nutrients for a human. The algorithm derives the required crop growth area per crew member under different dietary boundary conditions and the resulting nutrient supply is compared to reported diets from crops for spaceflight. The primary goal of this optimization is to find the minimal area required to supply all relevant macronutrients. The minimal area for the exact desired composition of macronutrients (carbohydrates, fats and proteins) was 106.86 m² using chard, lettuce, peanut, bell pepper, snap beans and spinach. If a deviation in the macronutrient composition is allowed the required area can be reduced to 39.88 m² of wheat and white potatoes. Since the variety of crops is a relevant factor for long term food supply, a limit of the maximum growth area per crop was introduced to derive a diet with more variety, which resulted in a minimal area of 57.04 m² using drybean, rice, snap beans, sweet potato, wheat and white potato. Based on this result, a further manual adjustment of the crop growth areas was performed to also introduce lettuce and tomato in the crops provided and adjust the remaining crop compositions to receive better macro- and micronutrient conformity while maintaining a crop growth area of 57 m². One major result of this analysis is that soybeans are not the most favorable crop with regard to protein and fat productivity and the focus of NASA crop selection for full nutrient supply on soybean results in exceedingly large required crop areas of 164.15 m². The resulting crop growth areas from both the optimization and literature are then analyzed as plant growth chambers (PGC) in the Life Support Trade-Off Tool (LiSTOT) of the institute of astronautic from the Technical University of Munich (TUM). LiSTOT calculates the impact of the PGC on an ISS based environmental control and life support system (ECLSS) using averaged steady state values for the plants from literature. Based on this result LiSTOT scales the physical chemical systems and calculates the resulting equivalent system mass (ESM) of the different cases. This approach allows the consideration of not only the PGC ESM, but also the impacts the PGC has on other ECLSS systems and their ESM. The ESM values for PGC were updated to assume LEDs instead of high pressure sodium lamps resulting in a new logistic mass of the PGC of 1.28 kg/(y m²) and a lower specific system mass of 87.7 kg/m². The mass balance analysis of carbon within the overall ECLSS lead to a reduction of the plant growth area to 50.6 m² and the break-even time with the ISS ECLSS was calculated to 87.2 years. With more optimistic assumptions for the LED and using urine as nutrient supply this time can be reduced to 14.6 years. The analysis also showed that the derived crop composition is not only favorable regarding nutrient supply but also with regard to the ESM and break-even time compared to previously reported crop compositions. Only the PGC with only wheat and white potatoes has a lower ESM but also provides a less balanced nutrient supply. This PGC is downscaled to 37.55 m² to achieve carbon balance and a break-even time of 38.4 years or 10.3 years with the optimistic assumptions.

A Low-Pressure, N2/CO2 Atmosphere Is Suitable for Cyanobacterium-Based Life-Support Systems on Mars.

The leading space agencies aim for crewed missions to Mars in the coming decades. Among the associated challenges is the need to provide astronauts with life-support consumables and, for a Mars exploration program to be sustainable, most of those consumables should be generated on site. Research is being done to achieve this using cyanobacteria: fed from Mars's regolith and atmosphere, they would serve as a basis for biological life-support systems that rely on local materials. Efficiency will largely depend on cyanobacteria's behavior under artificial atmospheres: a compromise is needed between conditions that would be desirable from a purely engineering and logistical standpoint (by being close to conditions found on the Martian surface) and conditions that optimize cyanobacterial productivity. To help identify this compromise, we developed a low-pressure photobioreactor, dubbed Atmos, that can provide tightly regulated atmospheric conditions to nine cultivation chambers. We used it to study the effects of a 96% N2, 4% CO2 gas mixture at a total pressure of 100 hPa on Anabaena sp. PCC 7938. We showed that those atmospheric conditions (referred to as MDA-1) can support the vigorous autotrophic, diazotrophic growth of cyanobacteria. We found that MDA-1 did not prevent Anabaena sp. from using an analog of Martian regolith (MGS-1) as a nutrient source. Finally, we demonstrated that cyanobacterial biomass grown under MDA-1 could be used for feeding secondary consumers (here, the heterotrophic bacterium E. coli W). Taken as a whole, our results suggest that a mixture of gases extracted from the Martian atmosphere, brought to approximately one tenth of Earth's pressure at sea level, would be suitable for photobioreactor modules of cyanobacterium-based life-support systems. This finding could greatly enhance the viability of such systems on Mars.

Exploiting a perchlorate-tolerant desert cyanobacterium to support bacterial growth for in situ resource utilization on Mars

AbstractThe presence of perchlorate in the Martian soil may limit in-situ resource utilization (ISRU) technologies to support human outposts. In order to exploit the desiccation, radiation-tolerant cyanobacterium Chroococcidopsis in Biological Life Support Systems based on ISRU, we investigated the perchlorate tolerance of Chroococcidopsis sp. CCMEE 029 and its derivative CCMEE 029 P-MRS. This strain was obtained from dried cells mixed with Martian regolith simulant and exposed to Mars-like conditions during the BIOMEX space experiment. After a 55-day exposure of up to 200 mM perchlorate ions, a tolerance threshold value of 100 mM perchlorate ions was identified for both Chroococcidopsis strains. After 40-day incubation, a Mars-relevant perchlorate concentration of 2.4 mM perchlorate ions, provided as a 60 and 40% mixture of Mg- and Ca-perchlorate, had no negative effect on the growth rate of the two strains. A proof-of-concept experiment was conducted using Chroococcidopsis lysate in ISRU technologies to feed a heterotrophic bacterium, i.e. an Escherichia coli strain capable of metabolizing sucrose. The sucrose content was fivefold increased in Chroococcidopsis cells through air-drying and the yielded lysate successfully supported the bacterial growth. This suggested that Chroococcidopsis is a suitable candidate for ISRU technologies to support heterotrophic BLSS components in a Mars-relevant perchlorate environment that would prove challenging to many other cyanobacteria, allowing a ‘live off the land’ approach on Mars.

Bacterial Growth at Low Pressure: A Short Review

Biological life-support systems could greatly increase the sustainability of crewed missions to the Moon or Mars. Understanding how bacteria react to hypobaria is critical to their optimization: if enclosed within crewed compartments, microbial modules may be exposed to the lower-than Earth atmospheric pressure considered for future space vehicles and habitats and, if deployed outside, they would best rely on a low pressure to minimize both engineering constraints and risks of leakage. Bacterial behavior at low pressures is of relevance to other fields as well, both within astrobiology (e.g., habitability and planetary protection) and outside of it (e.g., aerobiology and food preservation). Unfortunately, while microbial survival under vacuum has been largely investigated, little work has focused on metabolism at low but growth-permissive pressures. Nonetheless, recent studies brought some insights. Limits were outlined: a few bacterial species can grow just above water’s triple point, more can multiply down to around 25 mbar, and shifting pressure within 100 mbar to 1 bar seems not to largely affect growth of most species when the partial pressures of metabolizable gases are not limiting. Some mediating mechanisms have been proposed: hypobaria can affect bacteria by desiccation, via a reduced availability of specific gases, and through various other physico-chemical effects, interdependent and dependent on other environmental factors. A limited number of studies also gave insights into how bacteria cope with low pressure, and how much they can adapt to it. But, overall, much remains to be discovered on bacterial growth under hypobaric conditions.

THE LEGAL FRAMEWORK ENSURING PROTECTION OF THE NATURAL ENVIRONMENT

The article examines the legal basis for ensuring international security of the human environment in the context of globalization. Special attention is focused on planning and implementing a set of measures to preserve and optimize the natural environment, which are aimed at countering adverse changes in the past, present and future. The international environmental security declared by the United Nations in the modern period is evaluated differently by states that implement not always coordinated environmental policies on different continents of the world. As a result, the task of uniting the efforts of the international community in ensuring the safety of the human environment is becoming more urgent. The depletion of natural resources and the adverse effects of environmental degradation increase the challenges facing humanity. Such negative trends are recognized as land degradation, loss of biodiversity, shortage of drinking water, droughts, desertification and exacerbating new problems. Attention should be paid to climate change, which calls into question the ability of several countries to achieve the goal of sustainable development. Sea level rise, temperature rise and ocean acidification have a negative impact on low-lying coastal and island developing states and other coastal areas. There is a threat to the existence of biological life support systems for a number of communities.

Competitive Growth Assay of Mutagenized Chlamydomonas reinhardtii Compatible With the International Space Station Veggie Plant Growth Chamber.

A biological life support system for spaceflight would capture carbon dioxide waste produced by living and working in space to generate useful organic compounds. Photosynthesis is the primary mechanism to fix carbon into organic molecules. Microalgae are highly efficient at converting light, water, and carbon dioxide into biomass, particularly under limiting, artificial light conditions that are a necessity in space photosynthetic production. Although there is great promise in developing algae for chemical or food production in space, most spaceflight algae growth studies have been conducted on solid agar-media to avoid handling liquids in microgravity. Here we report that breathable plastic tissue culture bags can support robust growth of Chlamydomonas reinhardtii in the Veggie plant growth chamber, which is used on the International Space Station (ISS) to grow terrestrial plants. Live cultures can be stored for at least 1 month in the bags at room temperature. The gene set required for growth in these photobioreactors was tested using a competitive growth assay with mutations induced by short-wave ultraviolet light (UVC) mutagenesis in either wild-type (CC-5082) or cw15 mutant (CC-1883) strains at the start of the assay. Genome sequencing identified UVC-induced mutations, which were enriched for transversions and non-synonymous mutations relative to natural variants among laboratory strains. Genes with mutations indicating positive selection were enriched for information processing genes related to DNA repair, RNA processing, translation, cytoskeletal motors, kinases, and ABC transporters. These data suggest that modification of DNA repair, signal transduction, and metabolite transport may be needed to improve growth rates in this spaceflight production system.

Why did carbon become the pseudo-limiting factor in aquatic closed ecological systems?

Closure from the earth's atmosphere is a critical test of an ecosystem's ability to function. In our earlier testing of autotrophic Closed Ecological Systems (CESs), a C:N ratio of 26.4 (3.3 mM NaHCO3 and 0.125 mM NaNO3) supported algal and Daphnia populations for months, but developed extreme pH values (∼11 ungrazed, >10, grazed), suggesting that the systems were carbon-limited. Only approximately half the HCO3- (bicarbonate) would be expected to be available to green algae, the other portion becoming CO3−2 (carbonate). In an experiment described here, CESs were developed to explore a greater range of C:N ratios. To keep the medium from becoming too osmotically concentrated, NaNO3 was reduced to 0.0312 mM and NaHCO3 tested at 3.3, 13.2, and 26.4 mM, resulting in nominal C:N ratios of 105, 422, and 845. However, additional carbon was not beneficial to long-term survival of the organisms. The algal abundance was relatively insensitive to C:N ratio; greater concentrations of C were not beneficial. Daphnia populations were sensitive to C:N ratio and persisted longer at the lowest C:N ratio of 105. All of the C:N ratios tested in these CESs are outside of the expected range suggested from ecological studies, which is based on the Redfield Ratio of 6.625 C:N, the expected chemical composition of algae. Two potential explanations for the apparent high C demand in our CESs are suggested by the literature. The first is production of fatty algal cells, e.g., one of the algal species, Scenedesmus obliquus, is reported to produce high-lipid cells that could have a higher C:N ratio than the Redfield Ratio. The second is “carbon overconsumption,” which has been suggested for N-limited marine phytoplankton communities dominated by diatoms or nutrient deficient algal communities dominated by small cells that are under-represented by chlorophyll a measurements. The unexpected C dynamics found in our CES tests could be relevant to the design of biological life support systems that must be provisioned with adequate elements for long-term ecosystem functionality. If the actual demand for C is underestimated, its storage may be inadequate.

Eu:CROPIS \u2013 \u201cEuglena gracilis: Combined Regenerative Organic-food Production in Space\u201d - A Space Experiment Testing Biological Life Support Systems Under Lunar And Martian Gravity

Human space exploration needs stable life support systems for the supply of oxygen, water and food for each human explorer due to long term missions. The most promising approach for building stable life support systems is a combination of physico-chemical and biological systems. These hybrid systems combine the reliability of physico-chemical and the sustainability of biological life support systems. Also the disadvantages, which are the finite resources of physico-chemical and the imperfect reliability of biological systems, are mutually balanced. To improve the reliability of biological life support systems, a combination of different biological systems may stabilize the whole approach during long term operations. The satellite mission Eu:CROPIS (Euglena gracilis: Combined Regenerative Organic-food Production In Space) is a testbed for investigating the behavior of combined biological life support systems under the influence of altered gravity, here, Lunar and Martian gravity. The core systems are a biological trickle filter for processing urine into a fertilizer solution via nitrification and Euglena gracilis, a photosynthetic protist which is able to produce oxygen and biomass while protecting the whole system against high ammonia concentrations.

Evaluation of the Resistance of Chroococcidiopsis spp. to Sparsely and Densely Ionizing Irradiation.

Studying the resistance of cyanobacteria to ionizing radiation provides relevant information regarding astrobiology-related topics including the search for life on Mars, lithopanspermia, and biological life-support systems. Here, we report on the resistance of desert cyanobacteria of the genus Chroococcidiopsis, which were exposed (as part of the STARLIFE series of experiments) in both hydrated and dried states to ionizing radiation with different linear energy transfer values (0.2 to 200 keV/μm). Irradiation with up to 1 kGy of He or Si ions, 2 kGy of Fe ions, 5 kGy of X-rays, or 11.59 kGy of γ rays (60Co) did not eradicate Chroococcidiopsis populations, nor did it induce detectable damage to DNA or plasma membranes. The relevance of these results for astrobiology is briefly discussed. Key Words: Ionizing radiation-Linear energy transfer-Lithopanspermia-Cyanobacterial radioresistance-Chroococcidiopsis-Mars. Astrobiology 17, 118-125.

Operation of an enclosed aquatic ecosystem in the Shenzhou-8 mission

Long- term spaceflight needs reliable Biological life support systems (BLSS) to supply astronauts with enough food, fresh air and recycle wasters, but the knowledge about the operation pattern and controlling strategy is rear. For this purpose, a miniaturized enclosed aquatic ecosystem was developed and flown on the Chinese spaceship Shenzhou-8. The system with a total volume of about 60mL was separated into two chambers by means of a gas transparent membrane. The lower chamber was inoculated with Euglena gracilis cells, and the upper chamber was cultured with Chlorella cells and three snails. After 17.5 days flight, the samples were analyzed. It was found that all snails in the ground module (GM) were alive, while in the flight module (FM) only one snail survived. The total cell numbers, assimilation of nutrients like nitrogen and phosphorus, soluble proteins and carbohydrate contents showed a decrease in FM than in GM. The correlation analysis showed upper chambers of both FM and GM had the same positive and negative correlation factors, while differential correlation was found in lower chambers. These results suggested primary productivity in the enclosed system decreased in microgravity, accompanied with nutrients assimilation. The FM chamber endured lacking of domination species to sustain the system development and GM chamber endured richness in population abundance. These results implied photosynthesis intensity should be reduced to keep the system healthy. More Chlorella but less Euglena might be a useful strategy to sustain system stability. It is the first systematic analysis of enclosed systems in microgravity.

Microbial Community Dynamics and Response to Plant Growth-Promoting Microorganisms in the Rhizosphere of Four Common Food Crops Cultivated in Hydroponics.

Plant growth promoting microorganisms (PGPMs) of the plant root zone microbiome have received limited attention in hydroponic cultivation systems. In the framework of a project aimed at the development of a biological life support system for manned missions in space, we investigated the effects of PGPMs on four common food crops (durum and bread wheat, potato and soybean) cultivated in recirculating hydroponic systems for a whole life cycle. Each crop was inoculated with a commercial PGPM mixture and the composition of the microbial communities associated with their root rhizosphere, rhizoplane/endosphere and with the recirculating nutrient solution was characterised through 16S- and ITS-targeted Illumina MiSeq sequencing. PGPM addition was shown to induce changes in the composition of these communities, though these changes varied both between crops and over time. Microbial communities of PGPM-treated plants were shown to be more stable over time. Though additional development is required, this study highlights the potential benefits that PGPMs may confer to plants grown in hydroponic systems, particularly when cultivated in extreme environments such as space.

ARADISH - Development of a Standardized Plant Growth Chamber for Experiments in Gravitational Biology Using Ground Based Facilities

Plant development strongly relies on environmental conditions. Growth of plants in Biological Life Support Systems (BLSS), which are a necessity to allow human survival during long-term space exploration missions, poses a particular problem for plant growth, as in addition to the traditional environmental factors, microgravity (or reduced gravity such as on Moon or Mars) and limited gas exchange hamper plant growth. Studying the effects of reduced gravity on plants requires real or simulated microgravity experiments under highly standardized conditions, in order to avoid the influence of other environmental factors. Analysis of a large number of biological replicates, which is necessary for the detection of subtle phenotypical differences, can so far only be achieved in Ground Based Facilities (GBF). Besides different experimental conditions, the usage of a variety of different plant growth chambers was a major factor that led to a lack of reproducibility and comparability in previous studies. We have developed a flexible and customizable plant growth chamber, called ARAbidopsis DISH (ARADISH), which allows plant growth from seed to seedling, being realized in a hydroponic system or on Agar. By developing a special holder, the ARADISH can be used for experiments with Arabidopsis thaliana or a plant with a similar habitus on common GBF hardware, including 2D clinostats and Random Positioning Machines (RPM). The ARADISH growth chamber has a controlled illumination system of red and blue light emitting diodes (LED), which allows the user to apply defined light conditions. As a proof of concept we tested a prototype in a proteomic experiment in which plants were exposed to simulated microgravity or a 90° stimulus. We optimized the design and performed viability tests after several days of growth in the hardware that underline the utility of ARADISH in microgravity research.

Influence of different light-dark cycles on motility and photosynthesis of Euglena gracilis in closed bioreactors.

Abstract The unicellular photosynthetic freshwater flagellate Euglena gracilis is a promising candidate as an oxygen producer in biological life-support systems. In this study, the capacity of Euglena gracilis to cope with different light regimes was determined. Cultures of Euglena gracilis in closed bioreactors were exposed to different dark-light cycles (40 W/m(2) light intensity on the surface of the 20 L reactor; cool white fluorescent lamps in combination with a 100 W filament bulb): 1 h-1 h, 2 h-2 h, 4 h-4 h, 6 h-6 h, and 8 h-16 h, respectively. Motility and oxygen development in the reactors were measured constantly. It was found that, during exposure to light-dark cycles of 1 h-1 h, 2 h-2 h, 4 h-4 h, and 6 h-6 h, precision of gravitaxis as well as the number of motile cells increased during the dark phase, while velocity increased in the light phase. Oxygen concentration did not yet reach a plateau phase. During dark-light cycles of 8 h-16 h, fast changes of movement behavior in the cells were detected. The cells showed an initial decrease of graviorientation after onset of light and an increase after the start of the dark period. In the course of the light phase, graviorientation increased, while motility and velocity decreased after some hours of illumination. In all light profiles, Euglena gracilis was able to produce sufficient oxygen in the light phase to maintain the oxygen concentration above zero in the subsequent dark phase.

O2 evolution and cyclic electron flow around photosystem I in long-term ground batch culture of Euglena gracilis

Based on the purpose of better exploring the function of green producers in the closed aquatic biological life support system, the condition of dynamic O2 evolution and performance of cyclic electron flow around photosystem I (CEF-PSI) in long-term ground batch culture of Euglena gracilis were studied, the relationship between linear electron flow (LEF) and CEF-PSI was revealed, the function of CEF-PSI was investigated. Excellent consistency in O2 evolution pattern was observed in cultures grown in both closed and open containers, O2 evolution was strictly suppressed in phase 1, but the rate of it increased significantly in phase 2. CEF-PSI was proposed to be active during the whole course of cultivation, even in the declining phase 3, it still operated at the extent of 47–55%. It is suggested that the relationship between LEF and CEF-PSI is not only competition but also reciprocity. CEF-PSI was proposed to contribute to the considerable growth in phase 1; it was also suggested to play an important protective role against photosystem II (PSII) photoinhibition at the greatly enhanced level (approximately 80–95%) on the 2nd day. Our results in this research suggest that E. gracilis had very particular photosynthetic characteristics, the strict O2 evolution suppression in the initial culture phase might be a special light acclimation behavior, and CEF-PSI could be an important mechanism involved in this kind of adaptation to the changeable light environment.