In recent times Euglena gracilis Z was employed as primary producer in closed environmental life-support system (CELSS), e.g. in space research. The photosynthetic unicellular flagellate is not capable of utilizing nitrate, nitrite, and urea as nitrogen source. Therefore, ammonium is supplied as an N-source in the lab (provided as diammonium-dihydrogenphosphate, (NH4)2HPO4) to E. gracilis cultures. While nitrate exerts low toxicity to organisms, ammonium is harmful for many aquatic organisms especially, at high pH-values, which causes the ionic NH4+ (low toxicity) to be partially transformed into the highly toxic ammonia, NH3. In earlier reports, Euglena gracilis was described to grow with various amino acids as sole N-source. Our aim was to investigate alternatives for (NH4)2HPO4 as N-source with lower toxicity for organisms co-cultivated with Euglena in a CELSS. The growth kinetics of Euglena gracilis cultures was determined in the presence of different amino acids (glycine, glutamine, glutamic acid, leucine, and threonine). In addition, uptake of those amino acids by the cells was measured. Cell growth in the presence of glycine and glutamine was quite comparable to the growth in (NH4)2HPO4 containing cultures while a delay in growth was observed in the presence of leucine and threonine. Unlike, aforementioned amino acids glutamate consumption was very poor. Cell density and glutamate concentration were almost unaltered throughout the experiment and the culture reached the stationary phase within 8 days. The data are compared with earlier studies in which utilization of amino acids in Euglena gracilis was investigated. All tested amino acids (glutamate with limitations) were found to have the potential of being an alternative N-source for Euglena gracilis. Hence, these amino acids can be used as a non-toxic surrogate for (NH4)2HPO4.

The German Aerospace Center (DLR) enabled German participation in the joint space campaign on the unmanned Shenzhou 8 spacecraft in November 2011. In this report, the effect of microgravity on Euglena gracilis cells is described. Custom-made dual compartment cell fixation units (containing cells in one chamber and fixative - RNA lysis buffer - in another one) were enclosed in a small container and placed in the Simbox incubator, which is an experiment support system. Cells were fixed by injecting them with fixative at different time intervals. In addition to stationary experiment slots, Simbox provides a 1 g reference centrifuge. Cell fixation units were mounted in microgravity and 1 g reference positions of Simbox. Two Simbox incubators were used, one for space flight and the other as ground reference. Cells were fixed soon after launch and shortly before return of the spaceship. Due to technical problems, only early in-flight samples (about 40 min after launch microgravity and corresponding 1 g reference) were fully mixed with fixative, therefore only data from those samples are presented. Transcription of several genes involved in signal transduction, oxidative stress defence, cell cycle regulation and heat shock responses was investigated with quantitative PCR. The data indicate that Euglena cells suffer stress upon short-term exposure to microgravity; various stress-induced genes were up-regulated. Of 32 tested genes, 18 were up-regulated, one down-regulated and the rest remained unaltered. These findings are in a good agreement with results from other research groups using other organisms.

Space radiation has been monitored successfully using the Radiation Risks Radiometer-Dosimeter (R3D) installed at the ESA EXPOSE-R (R3DR) facility outside of the Russian Zvezda module of the International Space Station (ISS) between March 2009 and January 2011. R3DR is a Liulin type spectrometer–dosimeter with a single Si PIN detector 2cm2 of area and 0.3mm thick. The R3DR instrument accumulated about 2 million measurements of the absorbed dose rate and flux of 10s resolution. The total external and internal shielding before the detector of R3DR device is 0.41gcm−2. The calculated stopping energy of normally incident particles to the detector is 0.78MeV for electrons and 15.8MeV for protons. After the Coronal Mass Ejection (CME) at 09:54 UTC on 3 April 2010, a shock was observed at the ACE spacecraft at 0756 UTC on 5 April, which led to a sudden impulse on Earth at 08:26 UTC. Nevertheless, while the magnetic substorms on 5 and 6 of April were moderate; the second largest in history of GOES fluence of electrons with energy >2MeV was measured. The R3DR data show a relatively small amount of relativistic electrons on 5 April. The maximum dose rate of 2323μGyday−1 was reached on 7 April; by 9 April, a dose of 6600μGy was accumulated. By the end of the period on 7 May 2010 a total dose of 11,587μGy was absorbed. Our data were compared with AE-8 MIN, CRESS and ESA-SEE1 models using SPENVIS and with similar observations on American, Japanese and Russian satellites.

The paper presents observations of relativistic electron precipitations (REP) on the International Space Station (ISS) obtained by three Bulgarian-built instruments flown in 2001 and 2008–2010. The first data are from the Liulin-E094 instrument flown in May–August 2001 inside the US laboratory module of the ISS. Next the time profiles of the REP-generated daily fluences and the absorbed doses at the orbit of ISS during the period February 2008–August 2010 are analyzed in dependence of the daily Ap index and compared with the daily relativistic electron fluence with energies of more than 2MeV measured by the GOES. The REP in April 2010 being the second largest in GOES history (with a >2MeV electron fluence event) is specially studied.

The unicellular freshwater flagellate Euglena gracilis shows negative gravitactic behavior. Previous experiments have revealed that the orientation is most likely an active physiological process in which the beating pattern of the flagellum is controlled by gravity and mediated by a change in the calcium concentration inside the cell. In a signal transduction chain, the calcium signal activates a calmodulin, which in turn raises the concentration of cAMP. This alters the beating pattern of the flagellum; reorientation is therefore not a passive process driven by buoyancy. In a recent parabolic flight experiment (ESA 45th parabolic flight campaign), we observed the beating of the flagellum with a high-resolution light microscope. Transition from hyper g to μg as well as from μg to hyper g caused a change of the beating pattern of the flagellum, which confirmed the physiological nature of the process. In μg cells stopped moving the flagellum or tried to reorient, while in hyper g, the cells realigned consecutively. The reaction times for the flagellar responses in previous experiments are confirmed.

Solar and space radiation have been monitored using the R3D-B2 radiation risks radiometer-dosimeter on board a recent space flight on the Russian satellite Foton M2 within the ESA Biopan 5 facility mounted on the outside of the satellite exposed to space conditions. The solar radiation has been assayed in four wavelength bands (UV-C, 170–280nm, UV-B, 280–315nm), UV-A (315–400nm) and PAR (photosynthetic active radiation, 400–700nm). The data show an increasing tumbling rotation of the satellite during the mission. The photodiodes do not show a cosine response to the incident light which has been corrected. After calibration of the signals using the extraterrestrial spectrum, doses have been calculated for each orbit, for each day and for the total mission as basic data for the biological material which has been exposed in parallel in the Biopan facility. Cosmic ionizing radiation has been monitored and separated in 256 deposited energy spectra, which were further used for determination of the absorbed dose rate and flux. Basic data tables were prepared to be used by other Biopan 5 experiments. The paper summarizes the results for the Earth radiation environment at the altitude (262–304km) of the Foton M2 spacecraft. Comparisons with the predictions of NASA Earth radiation environment experimental models AE-8 and AP-8, and the PSB97 model are also presented, which calculate the fluxes of ionizing radiation from a simulation. AP-8 is a model for trapped radiation.

Sounding rockets are valuable experimental platforms for investigation of gravity-related physiological mechanism in living organisms. The obtained microgravity quality is excellent and the time scale of 6 -14 min microgravity is sufficient to examine various physiological parameters. Freefall or space experiments are the only possibility to avoid gravity and to obtain mechano-sensitive structures in a non-influenced state. Our group uses sounding rocket experiments to investigate the gravity-oriented movement behavior of the unicellular flagellate Euglena gracilis. In intensive laboratory experiments and during the course of eight TEXUS and two MAXUS campaigns it was found that the movement of the cells with respect to the gravity vector is controlled by an active physiological mechanism. The. experiments indicated possible elements of a signal transduction chain, which is presently under investigation by means of molecular biological methods.

The motile behavior of the unicellular photosynthetic flagellate Euglena gracilis was studied during a two-week mission on the Russian satellite Foton M2. The precision of gravitactic orientation was high before launch and, as expected, the cells were unoriented during microgravity. While after previous short-term TEXUS flights the precision of orientation was as high as before launch, it took several hours for the organisms to regain their gravitaxis. Also the percentage of motile cells and the swimming velocity of the remaining motile cells were considerably lower than in the ground control. In preparatory experiments the flagellate Euglena was shown to produce considerable amounts of photosynthetically generated oxygen. In a coupling experiment in a prototype for a planned space mission on Foton M3, the photosynthetic producers were shown to supply sufficient amounts of oxygen to a fish compartment with 35 larval cichlids, Oreochromis mossambicus.