Micro-Ecological Life Support System Alternative Research Articles

Whole transcriptome analysis highlights nutrient limitation of nitrogen cycle bacteria in simulated microgravity

Regenerative life support systems (RLSS) will play a vital role in achieving self-sufficiency during long-distance space travel. Urine conversion into a liquid nitrate-based fertilizer is a key process in most RLSS. This study describes the effects of simulated microgravity (SMG) on Comamonas testosteroni, Nitrosomonas europaea, Nitrobacter winogradskyi and a tripartite culture of the three, in the context of nitrogen recovery for the Micro-Ecological Life Support System Alternative (MELiSSA). Rotary cell culture systems (RCCS) and random positioning machines (RPM) were used as SMG analogues. The transcriptional responses of the cultures were elucidated. For CO2-producing C. testosteroni and the tripartite culture, a PermaLifeTM PL-70 cell culture bag mounted on an in-house 3D-printed holder was applied to eliminate air bubble formation during SMG cultivation. Gene expression changes indicated that the fluid dynamics in SMG caused nutrient and O2 limitation. Genes involved in urea hydrolysis and nitrification were minimally affected, while denitrification-related gene expression was increased. The findings highlight potential challenges for nitrogen recovery in space.

Biowaste recycling strategies for regenerative life support system: An overview

Space missions are expanding their horizons towards green energy. At the same time humans are expanding their invasion beyond the earth’s orbit and envisage to have a habitat on other planets like Mars. This is possible only when there is a continuous efflux of human biowaste and influx of vital and breathable air, food and water for the habitants. The current scenario of space toilets is limited to recycling of human urine to drinkable water by refluxing the human liquid waste via Micro-Ecological Life Support System Alternative (MELiSSA) in a closed loop. On the offset, the human biowaste is thrown in space adding into space waste leading to another causes of concern for the space environment. To add up if human biowaste is recycled via photosynthetic microalgal microbial fuel cell integrated into MELiSSA project, it would be very useful since not only the microalgae will assimilate CO2 exhaled by crew members but also give O2 and edible biomass for their survival in the spacecraft. Simultaneously, this might reduce the payload during space voyage. The novelty of cultivating microalgae in spacecrafts for bioregenerative life support lies in further cultivating microalgae in Mars for its terraformation to planet Earth.

Integration of Nitrifying, Photosynthetic and Animal Compartments at the MELiSSA Pilot Plant

MELiSSA (Micro Ecological Life Support System Alternative) is developing bioregenerative Life Support technologies for long-term Space missions. The MELiSSA concept is conceived as a loop with several compartments, each one performing a specific function, providing all together edible material production, atmosphere regeneration and water recovery with a concomitant use of wastes, i.e., CO2 and organic wastes. Each one of the compartments is colonized with specific bacteria or higher plants depending on its specific function. The MELiSSA Pilot Plant is a facility designed for the terrestrial demonstration of this concept, hosting laboratory rats as a crew mock-up mimicking the respiration of humans. Currently, the MELiSSA Pilot Plant focus on the integration of three compartments: Compartment 3 (nitrifying packed-bed bioreactor based on the co-culture of immobilized Nitrosomonas europaea and Nitrobacter winogradsky), compartment 4a (an air-lift photobioreactor for the culture of the edible cyanobacteria Limnospira indica with concomitant oxygen production) and Compartment 5 (an animal isolator with rats as mock-up crew). The output from these tests shows a high robustness and reliability and the performance of oxygen producing and oxygen consuming compartments is successfully demonstrated under transitory and steady-state conditions. This contribution reports on the current state of development of the MELiSSA Pilot Plant Facility and the most recent results of the integration work.

Development of Nitrogen Recycling Strategies for Bioregenerative Life Support Systems in Space.

To enable long-distance space travel, the development of a highly efficient and robust system to recover nutrients from waste streams is imperative. The inability of the current physicochemical-based environmental control and life support system (ECLSS) on the ISS to produce food in situ and to recover water and oxygen at high enough efficiencies results in the need for frequent resupply missions from Earth. Therefore, alternative strategies like biologically-based technologies called bioregenerative life support systems (BLSSs) are in development. These systems aim to combine biological and physicochemical processes, which enable in situ water, oxygen, and food production (through the highly efficient recovery of minerals from waste streams). Hence, minimalizing the need for external consumables. One of the BLSS initiatives is the European Space Agency’s (ESA) Micro-Ecological Life Support System Alternative (MELiSSA). It has been designed as a five-compartment bioengineered system able to produce fresh food and oxygen and to recycle water. As such, it could sustain the needs of a human crew for long-term space exploration missions. A prerequisite for the self-sufficient nature of MELiSSA is the highly efficient recovery of valuable minerals from waste streams. The produced nutrients can be used as a fertilizer for food production. In this review, we discuss the need to shift from the ECLSS to a BLSS, provide a summary of past and current BLSS programs and their unique approaches to nitrogen recovery and processing of urine waste streams. In addition, compartment III of the MELiSSA loop, which is responsible for nitrogen recovery, is reviewed in-depth. Finally, past, current, and future related ground and space demonstration and the space-related challenges for this technology are considered.

Trade-off analysis of phase separation techniques for advanced life support systems in space

Phase separation in multiphase flows in space systems is a challenging task due to the absence of buoyancy. Several phase separation approaches have been presented in the last years given the important role that systems containing multiphase flows will play in future space missions. We present a review of these techniques and a trade-off analysis for their application in life support systems and, in particular, in the MELiSSA (Micro Ecological Life Support System Alternative) photosynthesis bioreactor. The candidate approaches are evaluated, both quantitatively and qualitatively, according to the defined requirements and criteria. The outcome of the trade-off analysis shows passive static and acoustic techniques as the most recommended methods to carry out phase separation in the considered bioreactor.

Hierarchical Control of Space Closed Ecosystems: Expanding Microgrid Concepts to Bioastronautics

One of the main challenges of human space exploration is the development of artificial ecosystems, which can be used as life support systems (LSSs) to enable long-duration human space missions. In an open LSS, no food generation or waste treatment is provided in space, and supplies from Earth are necessary. According to Figure 1, considering the approximate metabolic consumables and hygiene water as well as the number of crewmembers [1], a huge mass would be required to be transported from Earth, which brings the necessity of a regenerative or closed LSS [2]-[4]. Closed ecological systems (CESs) are ecosystems without any matter exchange with the outside environment [2]. The most advanced humanmade CESs include Advanced Life Support System Test Bed (ALSSTB) (the NASA Johnson Space Research Center, Houston, Texas), Biosphere 2 (Oracle, Arizona), BIOS-3 (Krasnoyarsk, Russia-no longer operative), the Closed Ecology Experiment Facility (CEEF) complex (Rokkasho, Japan), the Micro-Ecological Life Support System Alternative (MELiSSA) Pilot Plant (MPP) (Universitat Aut?noma de Barcelona, Spain), and the Concordia Antarctica Station, which are different from one another with respect to their complexity, size, and degree of closure [2]. CESs are necessary for long-term manned space missions, which aim to minimize support from Earth. They are composed of several specific compartments that, together, reproduce the main functionalities of an ecological system in a continuous mode of operation and under controlled conditions.

Continuous controlled long-term operation and modeling of a closed loop connecting an air-lift photobioreactor and an animal compartment for the development of a life support system

The MELiSSA (MicroEcological Life Support System Alternative) project is developing a closed regenerative life support system for long-term space missions by considering the integration of six biological compartments tested in a dedicated pilot plant. The technological effort of building such a closed and sustainable ecological system can also have relevant applications for intensive circular resources reutilization at terrestrial level. In this work, the continuous operation and gas phase connection of two elements of the loop (83 L air-lift Limnospira indica photobioreactor (PBR) and a rat isolator (mock crew)) is performed and modelled. The model includes PBR hydrodynamic characterization, gas-liquid mass transfer and cyanobacteria growth, crew consumption and a control system adjusting light intensity according to oxygen demand. The model is validated in a series of tests where crew compartment oxygen setpoints are sequentially changed to test the global dynamics. The obtained results show a good model performance, as indicated in the low relative error (≤ 0.06) and the high Pearson correlation coefficient and Willmott-d-index obtained for the main variable of the system (0.98–1.00), oxygen concentration, in all cases.

Reactivation of Microbial Strains and Synthetic Communities After a Spaceflight to the International Space Station: Corroborating the Feasibility of Essential Conversions in the MELiSSA Loop.

To sustain human deep space exploration or extra-terrestrial settlements where no resupply from the Earth or other planets is possible, technologies for in situ food production, water, air, and waste recovery need to be developed. The Micro-Ecological Life Support System Alternative (MELiSSA) is such a Regenerative Life Support System (RLSS) and it builds on several bacterial bioprocesses. However, alterations in gravity, temperature, and radiation associated with the space environment can affect survival and functionality of the microorganisms. In this study, representative strains of different carbon and nitrogen metabolisms with application in the MELiSSA were selected for launch and Low Earth Orbit (LEO) exposure. An edible photoautotrophic strain (Arthrospira sp. PCC 8005), a photoheterotrophic strain (Rhodospirillum rubrum S1H), a ureolytic heterotrophic strain (Cupriavidus pinatubonensis 1245), and combinations of C. pinatubonensis 1245 and autotrophic ammonia and nitrite oxidizing strains (Nitrosomonas europaea ATCC19718, Nitrosomonas ureae Nm10, and Nitrobacter winogradskyi Nb255) were sent to the International Space Station (ISS) for 7 days. There, the samples were exposed to 2.8 mGy, a dose 140 times higher than on the Earth, and a temperature of 22°C ± 1°C. On return to the Earth, the cultures were reactivated and their growth and activity were compared with terrestrial controls stored under refrigerated (5°C ± 2°C) or room temperature (22°C ± 1°C and 21°C ± 0°C) conditions. Overall, no difference was observed between terrestrial and ISS samples. Most cultures presented lower cell viability after the test, regardless of the type of exposure, indicating a harsher effect of the storage and sample preparation than the spaceflight itself. Postmission analysis revealed the successful survival and proliferation of all cultures except for Arthrospira, which suffered from the premission depressurization test. These observations validate the possibility of launching, storing, and reactivating bacteria with essential functionalities for microbial bioprocesses in RLSS.

Sustainable natural production of vitamins for human consumption in long space missions using synthetic ecology approaches

The MELiSSA (Micro Ecological Life Support System Alternative) project aims to create a closed loop system, capable of providing all the necessary food, water and oxygen for astronauts on long Space missions. The MELiSSA loop is comprised of four compartments, with compartment IVA containing photoautotrophic bacteria, such as Arthrospira platensis, a good source of oxygen, edible biomass and micronutrients. One important example of the latter is cobalamin (B12) deficiency of which can lead to pernicious anaemia and neurological systems, and thus would be detrimental to astronauts on long Space missions. The molecule is not made by plants or fungi, so the ultimate source of B12 in the environment is prokaryotes, and its synthesis requires over 20 enzymatic reactions. Many eukaryotic algae also require cobalamin for growth, and some species have been shown to accumulate the vitamin when grown in coculture with cobalamin synthesising bacteria. The aim of this project is to extend existing knowledge of algal-bacterial mutualisms involving cobalamin. Eukaryotic species such as Haematococcus pluvialis and Chlorella vulgaris, both certified as safe for human consumption, along with A. platensis will be investigated with different bacterial partners to maximise cobalamin accumulation. Not only will this research help provide adequate nutrition on long Space missions, it will also support nutritional supply on Earth with the rise of veganism, as well as, aiding in understanding the dynamics of algal-bacterial mutualisms, which is of interest in terms of nutrient cycling in the environment.

Greenhouse Module for Space System: A Lunar Greenhouse Design

Abstract In the next 10 to 20 years humankind will return to the Moon and/or travel to Mars. It is likely that astronauts will eventually build permanent settlements there, as a base for long-term crew tended research tasks. It is obvious that the crew of such settlements will need food to survive. With current mission architectures the provision of food for longduration missions away from Earth requires a significant number of resupply flights. Furthermore, it would be infeasible to provide the crew with continuous access to fresh produce, specifically crops with high water content such as tomatoes and peppers, on account of their limited shelf life. A greenhouse as an integrated part of a planetary surface base would be one solution to solve this challenge for long-duration missions. Astronauts could grow their own fresh fruit and vegetables in-situ to be more independent from supply from Earth. This paper presents the results of the design project for such a greenhouse, which was carried out by DLR and its partners within the framework of the Micro-Ecological Life Support System Alternative (MELiSSA) program. The consortium performed an extensive system analysis followed by a definition of system and subsystem requirements for greenhouse modules. Over 270 requirements were defined in this process. Afterwards the consortium performed an in-depth analysis of illumination strategies, potential growth accommodations and shapes for the external structure. Five different options for the outer shape were investigated, each of them with a set of possible internal configurations. Using the Analytical Hierarchy Process, the different concept options were evaluated and ranked against each other. The design option with the highest ranking was an inflatable outer structure with a rigid inner core, in which the subsystems are mounted. The inflatable shell is wrapped around the core during launch and transit to the lunar surface. The paper provides an overview of the final design, which was further detailed in a concurrent engineering design study. During the study, the subsystem parameters (e.g. mass, power, performance) were calculated and evaluated. The results of the study were further elaborated, leading to a lunar greenhouse concept that fulfils all initial requirements. The greenhouse module has a total cultivation area of more than 650 m² and provides more than 4100 kg of edible dry mass over the duration of the mission. Based on the study, the consortium also identified technology and knowledge gaps (not part of this paper), which have to be addressed in future projects to make the actual development of such a lunar greenhouse, and permanent settlements for long-term human-tended research tasks on other terrestrial bodies, feasible in the first place.

MELiSSA the minimal biosphere: Human life, waste and refuge in deep space

MELiSSA (Micro-Ecological Life Support System Alternative) is a long-term technology program of the European Space Agency. Its aim is to construct autonomous habitats in deep space, supplying astronauts with fresh air, water and food through continuous microbial recycling of human wastes. This article considers how anticipated futures of space travel and environmental survival are materialized in the project to engineer the minimal biosphere capable of reliably sustaining human life: a human/microbe association with the fewest possible species. We locate MELiSSA within a history of bio-infrastructures associated with colonisation projects: refugia in which organisms dislocated from their originary habitats are preserved. Analysis of MELiSSA’s sewage-composting technology suggests that the disordering complexity of human waste presents a formidable “bottle-neck” for the construction of the minimal biosphere, in turn suggesting our dependence on microbial communities (soil, the human gut) of potentially irreducible biocomplexity. MELiSSA researchers think of themselves as pragmatic enablers of space exploration, yet a wider family of space colonisation projects are now imagined in terms of the prospect that the Earth might cease to function as the minimal biosphere capable of supporting civilisation. MELiSSA’s politics of anticipation are paradoxical, promising technologies with which to escape from the Earth and through which it may be sustained.

Effects of the Extraterrestrial Environment on Plants: Recommendations for Future Space Experiments for the MELiSSA Higher Plant Compartment.

Due to logistical challenges, long-term human space exploration missions require a life support system capable of regenerating all the essentials for survival. Higher plants can be utilized to provide a continuous supply of fresh food, atmosphere revitalization, and clean water for humans. Plants can adapt to extreme environments on Earth, and model plants have been shown to grow and develop through a full life cycle in microgravity. However, more knowledge about the long term effects of the extraterrestrial environment on plant growth and development is necessary. The European Space Agency (ESA) has developed the Micro-Ecological Life Support System Alternative (MELiSSA) program to develop a closed regenerative life support system, based on micro-organisms and higher plant processes, with continuous recycling of resources. In this context, a literature review to analyze the impact of the space environments on higher plants, with focus on gravity levels, magnetic fields and radiation, has been performed. This communication presents a roadmap giving directions for future scientific activities within space plant cultivation. The roadmap aims to identify the research activities required before higher plants can be included in regenerative life support systems in space.

Soybean cultivation for Bioregenerative Life Support Systems (BLSSs): The effect of hydroponic system and nitrogen source

Soybean [Glycine max (L.) Merr.] is one of the plant species selected within the European Space Agency (ESA) Micro-Ecological Life Support System Alternative (MELiSSA) project for hydroponic cultivation in Biological Life Support Systems (BLSSs), because of the high nutritional value of seeds. Root symbiosis of soybean with Bradirhizobium japonicum contributes to plant nutrition in soil, providing ammonium through the bacterial fixation of atmospheric nitrogen. The aim of this study was to evaluate the effects of two hydroponic systems, Nutrient Film Technique (NFT) and cultivation on rockwool, and two nitrogen sources in the nutrient solution, nitrate (as Ca(NO3)2 and KNO3) and urea (CO(NH2)2), on root symbiosis, plant growth and seeds production of soybean. Plants of cultivar ‘OT8914’, inoculated with B. japonicum strain BUS-2, were grown in a growth chamber, under controlled environmental conditions.Cultivation on rockwool positively influenced root nodulation and plant growth and yield, without affecting the proximate composition of seeds, compared to NFT. Urea as the sole source of N drastically reduced the seed production and the harvest index of soybean plants, presumably because of ammonium toxicity, even though it enhanced root nodulation and increased the N content of seeds. In the view of large-scale cultivation for space colony on planetary surfaces, the possibility to use porous media, prepared using in situ resources, should be investigated. Urea can be included in the nutrient formulation for soybean in order to promote bacterial activity, however a proper ammonium/nitrate ratio should be maintained.

Modelled microgravity cultivation modulates N-acylhomoserine lactone production in Rhodospirillum rubrum S1H independently of cell density

The photosynthetic alphaproteobacterium Rhodospirillum rubrum S1H is part of the Micro-Ecological Life Support System Alternative (MELiSSA) project that is aiming to develop a closed life support system for oxygen, water and food production to support human life in space in forthcoming long-term space exploration missions. In the present study, R. rubrum S1H was cultured in a rotating wall vessel (RWV), simulating partial microgravity conditions on Earth. The bacterium showed a significant response to cultivation in simulated microgravity at the transcriptomic, proteomic and metabolic levels. In simulated microgravity conditions three N-acyl-l-homoserine lactones (C10-HSL, C12-HSL and 3-OH-C14-HSL) were detected in concentrations that were twice those detected under normal gravity, while no differences in cell density was detected. In addition, R. rubrum cultivated in modelled microgravity showed higher pigmentation than the normal gravity control, without change in culture oxygenation. When compared to randomized microgravity cultivation using a random positioning machine, significant overlap for the top differentially expressed genes and proteins was observed. Cultivation in this new artificial environment of simulated microgravity showed new properties of this well-known bacterium, including its first, to our knowledge, complete quorum-sensing-related N-acylhomoserine lactone profile.

Will Plants Grow on Moon or Mars?

The cultivation of plants in space and on the Moon and Mars implies exposure to physical factors that are different from Earth: radiation, gravity levels and magnetic fields. As part of the MELiSSA (Micro-Ecological Life Support System Alternative) project where higher plants represent one of the compartments of an enclosed life support system, literature has been reviewed to assemble the relevant knowledge within space plant research. This review has particularly focused on the effect of the physical factors mentioned above on higher plant morphology, anatomy, gene regulation and genetic damage. Radiation studies on ground have shown increased damages to plant cells, and magnetic field studies have indicated some stress responses and altered growth rates, although not conclusive. Both in space and on ground (clinostat experiments) there are inconsistent results regarding gene expression and plant morphology. Anatomical flaws on the cellular level such as a reduced proliferation, displaced statoliths, ovoid chloroplasts, progressive vacuolization, and altered cell walls have been observed in several experiments. A normal plant reproduction process in weightlessness is feasible with a properly designed hardware. The same can be expected with low gravity levels, like those on Moon and Mars. In conclusion, the published results show that plants will grow and reproduce in low Earth orbit, but they might experience genotoxic stress and anatomic changes. Longer space studies, in particular outside the geomagnetic field and its radiation belt, are needed in order to investigate potential adaption responses since many studies show that plants can adapt in one generation to extreme environments.

Soilless cultivation of soybean for Bioregenerative Life‐Support Systems: a literature review and the experience of the MELiSSA Project – Food characterisation Phase I

Higher plants play a key role in Bioregenerative Life-Support Systems (BLSS) for long-term missions in space, by regenerating air through photosynthetic CO2 absorption and O2 emission, recovering water through transpiration and recycling waste products through mineral nutrition. In addition, plants could provide fresh food to integrate into the crew diet and help to preserve astronauts' wellbeing. The ESA programme Micro-Ecological Life-Support System Alternative (MELiSSA) aims to conceive an artificial bioregenerative ecosystem for resources regeneration, based on both microorganisms and higher plants. Soybean [Glycine max (L.) Merr.] is one of the four candidate species studied for soilless (hydroponic) cultivation in MELiSSA, because of the high nutritional value of the seeds. Within the MELiSSA programme - Food characterisation Phase I, the aim of the research carried out on soybean at the University of Naples was to select the most suitable European cultivars for cultivation in BLSS. In this context, a concise review on the state-of-the-art of soybean cultivation in space-oriented experiments and a summary of research activity for the preliminary theoretical selection and subsequent agronomical evaluation of four cultivars will be presented in this paper.

Axenic Cultures of Nitrosomonas europaea and Nitrobacter winogradskyi in Autotrophic Conditions: a New Protocol for Kinetic Studies

As a part of a natural biological N-cycle, nitrification is one of the steps included in the conception of artificial ecosystems designed for extraterrestrial life support systems (LSS) such as Micro-Ecological Life Support System Alternative (MELiSSA) project, which is the LSS project of the European Space Agency. Nitrification in aerobic environments is carried out by two groups of bacteria in a two-step process. The ammonia-oxidizing bacteria (Nitrosomonas europaea) realize the oxidation of ammonia to nitrite, and the nitrite-oxidizing bacteria (Nitrobacter winogradskyi), the oxidation of nitrite to nitrate. In both cases, the bacteria achieve these oxidations to obtain an energy and reductant source for their growth and maintenance. Furthermore, both groups also use CO₂ predominantly as their carbon source. They are typically found together in ecosystems, and consequently, nitrite accumulation is rare. Due to the necessity of modeling accurately conversion yields and transformation rates to achieve a complete modeling of MELiSSA, the present study focuses on the experimental determination of nitrogen to biomass conversion yields. Kinetic and mass balance studies for axenic cultures of Nitrosomonas europaea and Nitrobacter winogradskyi in autotrophic conditions are performed. The follow-up of these cultures is done using flow cytometry for assessing biomass concentrations and ionic chromatography for ammonium, nitrite, and nitrate concentrations. A linear correlation is observed between cell count and optical density (OD) measurement (within a 10 % accuracy) validating OD measurements for an on-line estimation of biomass quantity even at very low biomass concentrations. The conversion between cell count and biomass concentration has been determined: 7.1 × 10¹² cells g dry matter (DM)⁻¹ for Nitrobacter and 6.3 × 10¹² cells g DM⁻¹ for Nitrosomonas. Nitrogen substrates and products are assessed redundantly showing excellent agreement for mass balance purposes and conversion yields determination. Although the dominant phenomena are the oxidation of NH₄⁺ into nitrite (0.95 mol mol N⁻¹ for Nitrosomonas europaea within an accuracy of 3 %) and nitrite into nitrate (0.975 mol mol N⁻¹ for Nitrobacter winogradskyi within an accuracy of 2 %), the Nitrosomonas europaea conversion yield is estimated to be 0.42 g DM mol N⁻¹, and Nitrobacter winogradskyi conversion yield is estimated to be 0.27 g DM mol N⁻¹. The growth rates of both strains appear to be dominated by the oxygen transfer into the experimental setups.

Soybean cultivar selection for Bioregenerative Life Support Systems (BLSS) – Theoretical selection

The development of plant-based Bioregenerative Life Support Systems (BLSS) is a requirement for the realization of long-duration exploratory-class manned missions in so far as they help fulfilling astronauts’ needs including nutritional demands, air regeneration and psychological support.The program ESA – MELiSSA (European Space Agency – Micro-Ecological Life Support System Alternative) aims to conceive an artificial bioregenerative ecosystem based on both microorganisms and higher plants. Soybean is one of the four crops studied within this program as a candidate for cultivation in forthcoming BLSS.Within this project, the aim of this study was to develop a methodology for the selection of soybean candidate cultivars for BLSS. Our scope was to identify an objective and repeatable procedure to choose the best cultivar at each time, overcoming the variability of the market supply. This purpose was pursued with an approach based on a two-steps procedure: (a) the development of an objective criterion for the selection of the most suitable soybean cultivars (cultivated varieties) based on theoretical considerations and (b) the behaviour evaluation of the 4 best cultivars with a cultivation trial in a controlled environment.In this paper, we report the first phase of the selection procedure. We started with a literature survey to look for data about environmental needs, potential yields and nutritional traits of soybean cultivars already tested in cultivation trials (disregarding Gene Modified Organisms). Afterwards, a preliminary screening based on information about the main European companies and the most commercialized cultivars, as well as on the criteria suggested by ESA, allowed to select 93 cultivars among the 297 admitted in EU. Finally, an algorithm, based on the relevance of each considered characteristic, was created to attribute a score to each cultivar and to rank it for the identification of the best cultivars for subsequent cultivation trials.

Toxicogenomic Response of Rhodospirillum rubrum S1H to the Micropollutant Triclosan

In the framework of the Micro-Ecological Life Support System Alternative (MELiSSA) project, a pilot study was performed to identify the effects of triclosan on the MELiSSA carbon-mineralizing microorganism Rhodospirillum rubrum S1H. Triclosan is a biocide that is commonly found in human excrement and is considered an emerging pollutant in wastewater and the environment. Chronic exposure to MELiSSA-relevant concentrations (> or =25 microg liter(-1)) of triclosan resulted in a significant extension of the lag phase of this organism but hardly affected the growth rate. Analytical determinations gave no indication of triclosan biodegradation during the growth experiment, and flow cytometric viability analyses revealed that triclosan is bacteriostatic and only slightly toxic to R. rubrum S1H. Using microarray analyses, the genetic mechanisms supporting the reversibility of triclosan-induced inhibition were scrutinized. An extremely triclosan-responsive cluster of four small adjacent genes was identified, for which there was up to 34-fold induction with 25 microg liter(-1) triclosan. These four genes, for which the designation microf (micropollutant-upregulated factor) is proposed, appear to be unique to R. rubrum and are shown here for the first time to be involved in the response to stress. Moreover, numerous other systems that are associated with the proton motive force were shown to be responsive to triclosan, but they were never as highly upregulated as the microf genes. In response to triclosan, R. rubrum S1H induced transcription of the phage shock protein operon (pspABC), numerous efflux systems, cell envelope consolidation mechanisms, the oxidative stress response, beta-oxidation, and carbonic anhydrase, while there was downregulation of bacterial conjugation and carboxysome synthesis genes. The microf genes and three efflux-related genes showed the most potential to be low-dose biomarkers.

Genome Sequence of the Edible Cyanobacterium Arthrospira sp. PCC 8005

We determined the genome sequence of Arthrospira sp. PCC 8005, a cyanobacterial strain of great interest to the European Space Agency for its nutritive value and oxygenic properties in the Micro-Ecological Life Support System Alternative (MELiSSA) biological life support system for long-term manned missions into space.