M. Lebert - Academia.edu (original) (raw)
Papers by M. Lebert
Life Sciences in Space Research, 2015
In recent times Euglena gracilis Z was employed as primary producer in closed environmental lifes... more In recent times Euglena gracilis Z was employed as primary producer in closed environmental lifesupport 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 Nsource in the lab (provided as diammonium-dihydrogenphosphate, (NH 4) 2 HPO 4) 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 NH 4 + (low toxicity) to be partially transformed into the highly toxic ammonia, NH 3. In earlier reports, Euglena gracilis was described to grow with various amino acids as sole N-source. Our aim was to investigate alternatives for (NH 4) 2 HPO 4 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 (NH 4) 2 HPO 4 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 (NH 4) 2 HPO 4 .
Photochemistry and Photobiology, 1998
The unicellular flagellate Euglena gracilis shows positive phototaxis at low fluence rates (510 W... more The unicellular flagellate Euglena gracilis shows positive phototaxis at low fluence rates (510 W m-2) and negative phototaxis at high fluence rates (2100 W m-2). Currently, retinal or flavidpterins are discussed as chromophores of the photoreceptor. When grown in the presence of 4 mM nicotine, a retinal inhibitor, for several generations, the cells still showed both responses, indicating that retinal is unlikely to be the chromophoric group of the photoreceptor responsible for phototaxis. The native flavin(s) can be substituted by growing the cells in roseoflavin dissolved in the medium. The absorption spectrum of roseoflavin extends well beyond the action spectrum for phototaxis (up to 600 nm). Excitation at wavelengths >550 nm does not cause phototactic orientation in control cells but causes both positive and negative phototaxis in roseoflavin-grown cells, indicating an uptake and assembly of the chromophore in the photoreceptor complex. The white mutant strain 122&5/1f, induced by streptomycin treatment, lacks flavins as indicated by fluorescence spectroscopy. The phototaxis-deficient phenotype cannot be complemented by the addition of external riboflavin. Fluorescence spectra of intact paraxonemal bodies (PAB) indicate that both pterins and flavins are involved in photoperception and that the excitation energy is efficiently funneled from the pterins to the flavins. This energy transfer is disrupted by solubilization of the PAB. In intact PAB flavins are not accessible to reducing or oxidizing substances, indicating that they are located inside the structure, while pterins are accessible, so that their localization can be assumed to be on the surface. The results described above are discussed with regard to the potential involvement of flavins and pterins as well as retinal in photoperception.
Photochemistry and Photobiology, 1985
A hardware and software system is described which is capable of automatically following the movem... more A hardware and software system is described which is capable of automatically following the movement of microorganisms and analyzing the deviation of individuals in a population from a predefined direction. The image of the moving organisms is viewed by a video camera, digitized in real time and stored in a dedicated video memory holding 512 X 256 pixels with 64 grey levels. A microcomputer has access to this video memory via four parallel ports. The software analyzes the position of an organism selected randomly and attempts to follow its track for a predefined period of time. If successful, it calculates the direction of movement and stores the data in a file for statistical analysis. Using this system, the movement of populations of the unicellular flagellate, Euglena gracilis, in unilateral and bilateral light beams has been studied and compared with the dark behavior. When irradiated from two opposite light sources of equal fluence rates half of the population swims towards either light source. However, when the light sources are oriented at an angle of 90" to each other the cells move on the resultant away from the light. These results confirm the shading hypothesis for negative phototaxis.
Botanica Acta, 1995
The effects of UV (280–400 nm) irradiation on phycobiliprotein composition have been studied in t... more The effects of UV (280–400 nm) irradiation on phycobiliprotein composition have been studied in two N2-fixing cyanobacteria, Anabaena sp. and Nostoc carmium, isolated from rice paddy fields in India. Phycobiliproteins were isolated and separated by sucrose density gradient centrifugation. After UV exposure the top fraction mainly contained carotenoids (absorption maximum at 485 nm), which first showed an increase in intensity and absorption and then a gradual decrease with increasing UV exposure in Anabaena sp., whereas, in Nostoc carmium this fraction showed a steady increase over the whole exposure time. The bottom fraction of both organisms mainly contained phycocyanin (absorption peak at 620 nm) which showed a steady decline in intensity, as well as absorption. Fluorescence excitation at 620 nm resulted in an emission at 650 nm which underwent a shift towards shorter wave-lengths with increasing UV-exposure time, indicating a disassembly of the phycobilisomal complex and of impaired energy transfer from accessory pigments to the reaction centers. SDS PAGE analysis of the fractions revealed a loss of high molecular mass linker proteins and low molecular mass (αβ monomers indicating that the phycobiliproteins, which function as accessory pigments for the operation of photosystem II, disassemble during UV irradiation.
Journal of Photochemistry and Photobiology B: Biology, 1997
The Erlanger flagellate test (EFT) is based on the green unicellular flagellate Euglena gracilis.... more The Erlanger flagellate test (EFT) is based on the green unicellular flagellate Euglena gracilis. The organisms are cultivated in minimal medium and used in their stationary growth phase. In order to quantify the effects of toxic substances or solar UV radiation, several ...
Journal of plant physiology, 1999
Gravitaxis in unicellular microorganisms like Euglena gracilis has been known for more than 100 y... more Gravitaxis in unicellular microorganisms like Euglena gracilis has been known for more than 100 years. The current model explains this phenomenon on the basis of a specific density difference between cell body and surrounding medium. In order to test the feasibility of the ...
Electrophoresis, 1998
Phycobiliproteins are homologous chromoproteins which constitute the phycobilisomes, the light ha... more Phycobiliproteins are homologous chromoproteins which constitute the phycobilisomes, the light harvesting complexes of the photosynthetic apparatus in cyanobacteria, rhodophyta and cryptophyta. In the present work, phycocyanin (PC) and phycoerythrin (PE) from a Nostoc species are proposed as protein markers for electrophoretic techniques. Phycocyanin is a blue-colored phycobiliprotein; it carries phycocyanobilin as chromophoric group and is composed of two subunits, alpha and beta, with Mr of 14000 and 17000, respectively. In contrast, the PE subunits, having a similar Mr of 21000, are deep rose chromoproteins and carry phycoerythrobilin residues. Both low molecular weight phycobiliproteins are also suitable for monitoring protein blotting and the focusing time of protein samples during isoelectric focusing as internal markers. The PE subunits which form a single broad band after sodium dodecyl sulfate-polyacrylamide gel electrophoresis have different isoelectric points, and they form two visible bands when they reach their isoelectric point. The phycobilisomes constitute up to 50% of the total protein in cyanobacteria and their content in PC or PE can be up- or down-regulated by using different light conditions (chromatic adaptation).
Astrobiology, 2013
Research in microgravity is indispensable to disclose the impact of gravity on biological process... more Research in microgravity is indispensable to disclose the impact of gravity on biological processes and organisms. However, research in the near-Earth orbit is severely constrained by the limited number of flight opportunities. Ground-based simulators of microgravity are valuable tools for preparing spaceflight experiments, but they also facilitate stand-alone studies and thus provide additional and cost-efficient platforms for gravitational research. The various microgravity simulators that are frequently used by gravitational biologists are based on different physical principles. This comparative study gives an overview of the most frequently used microgravity simulators and demonstrates their individual capacities and limitations. The range of applicability of the various ground-based microgravity simulators for biological specimens was carefully evaluated by using organisms that have been studied extensively under the conditions of real microgravity in space. In addition, current heterogeneous terminology is discussed critically, and recommendations are given for appropriate selection of adequate simulators and consistent use of nomenclature.
Journal of plant physiology, 1997
Euglena gracilis, a unicellular, photosynthetic flagellate, orients itself by means of gravi- and... more Euglena gracilis, a unicellular, photosynthetic flagellate, orients itself by means of gravi- and phototaxis to reach and stay in regions optimal for survival and growth. An improved version of the slow rotating centrifuge microscope, NIZEMI, was used to test wild type and mutant strains for their responses to hypergravity. Wild type cells could actively move against the acceleration vector up to 8.5 gn and were centrifuged down at higher rates. Even at 10.5 gn, the highest value tested, cells were still negative gravitactically oriented as shown by video images. In contrast, all mutant strains as well as Astasia longa, a close relative of Euglena, could move against the acceleration vector under all conditions tested. With increasing accelerations the mean orientation of the populations shifted according to a vectorial addition of gravity and acceleration. The r-value, a statistical measure of the orientation of a population, increased with moderately increased acceleration rates a...
Euglena gracilis, a unicellular photosynthetic flagellate, serves as a model system in signal tra... more Euglena gracilis, a unicellular photosynthetic flagellate, serves as a model system in signal transduction research. To further study its complex gravitaxis, experiments under microgravity are desirable. In preparation for long-term experiments on a space station, an autonomous cultivation unit has been developed and the culture conditions and surveillance methods have been established. The running time of more than 600 d under closed conditions with light as the only source of energy confirmed the stability of the Euglena population and gave new insights into its behavior. Physicochemical parameters such as oxygen concentration, temperature and pH as well as physiological parameters including cell density, motility, gravitactic orientation and pigmentation were recorded on a frequent basis. The suitability of the botanical bioreaction to serve as an oxygen supplier for animals in a closed system was demonstrated.
International Journal of Molecular Sciences
All life forms have evolved under the constant force of gravity on Earth and developed ways to co... more All life forms have evolved under the constant force of gravity on Earth and developed ways to counterbalance acceleration load. In space, shear forces, buoyance-driven convection, and hydrostatic pressure are nullified or strongly reduced. When subjected to microgravity in space, the equilibrium between cell architecture and the external force is disturbed, resulting in changes at the cellular and sub-cellular levels (e.g., cytoskeleton, signal transduction, membrane permeability, etc.). Cosmic radiation also poses great health risks to astronauts because it has high linear energy transfer values that evoke complex DNA and other cellular damage. Space environmental conditions have been shown to influence apoptosis in various cell types. Apoptosis has important functions in morphogenesis, organ development, and wound healing. This review provides an overview of microgravity research platforms and apoptosis. The sections summarize the current knowledge of the impact of microgravity a...
Microorganisms
Due to the increasing development of antibiotic resistances in recent years, scientists search in... more Due to the increasing development of antibiotic resistances in recent years, scientists search intensely for new methods to control bacteria. Photodynamic treatment with porphyrins such as chlorophyll derivatives is one of the most promising methods to handle bacterial infestation, but their use is dependent on illumination and they seem to be more effective against Gram-positive bacteria than against Gram-negatives. In this study, we tested chlorophyllin against three bacterial model strains, the Gram-positive Bacillus subtilis 168, the Gram-negative Escherichia coli DH5α and E. coli strain NR698 which has a deficient outer membrane, simulating a Gram-negative “without” its outer membrane. Illuminated with a standardized light intensity of 12 mW/cm2, B. subtilis showed high sensitivity already at low chlorophyllin concentrations (≤105 cfu/mL: ≤0.1 mg/L, 106–108 cfu/mL: 0.5 mg/L), whereas E. coli DH5α was less sensitive (≤105 cfu/mL: 2.5 mg/L, 106 cfu/mL: 5 mg/L, 107–108 cfu/mL: ine...
Journal of Plant Physiology, 1999
Gravitaxis in unicellular microorganisms like Euglena gracilis has been known for more than 100 y... more Gravitaxis in unicellular microorganisms like Euglena gracilis has been known for more than 100 years. The current model explains this phenomenon on the basis of a specific densiry difference berween cell body and surrounding medium. In order to test the feasibiliry of the current model in terms of physical * Correspondence.
Journal of Photochemistry and Photobiology B: Biology, 2000
A network of three channel dosimeters has been installed in Europe and other continents to contin... more A network of three channel dosimeters has been installed in Europe and other continents to continuously and automatically monitor solar radiation in the UV-B (280 – 315 nm), UV-A (315 – 400 nm) and PAR (photosynthetic active radiation, 400 – 700 nm) wavelength ranges to follow long-term and short-term changes in the light climate. The instruments are housed in rugged cases to withstand extreme environments from the polar circle to the tropics. The entrance optic is based on an integrating sphere and the wavelength selection is done by appropriate filter and photodiode combinations. Software packages have been developed to poll the data, display them graphically and store them. Quality control is warranted by careful and frequent calibration of the instruments as well as national and international intercalibrations. The data are sent to a central server in Pisa from where they can be downloaded on the Internet free of charge. The network has been in operation for the last five years and has constantly been growing in numbers. The data are being used to extract important information on changing light climate conditions and the development of stratospheric ozone.
Journal of Plant Physiology, 1997
Three mutant strains of the phytoflagellate Euglena gracilis Z have been characterized in order t... more Three mutant strains of the phytoflagellate Euglena gracilis Z have been characterized in order to analyze the signal perception and signal transduction pathways involved in photo-and gravitaxis. Using the fluorescence of the chromophoric groups believed to be involved in photoperception (flavins and pterins) a method was developed for an in situ and in vivo detection of the paraxonemal body, the proposed location of the photoreceptor molecules. Two of the mutant strains, 1224-5/9f and 1224-511f, do not possess a stigma and also lack a paraxonemal body, as indicated by fluorescence measurements. The third strain, FB, has a small stigma, but only some cells contain a paraxonemal body. In contrast to the present hypothesis on photoorientation of Euglena, all strains were able to orient with respect to the light direction. However, the mutant strains did not show any orientation at low irradiances. At medium and high irradiances the strains 1224-5/9f and 1224-5I1f oriented perpendicular to the light direction (diaphototaxis) while cells of strain FB showed partly negative phototaxis and partly diaphototaxis. Diaphototaxis was never observed in the wild type strain. Strains 1224-5/9f and 1224-511f showed normal graviresponses compared with the wild type. Astasia tonga, a nonphototactic relative of E. gracilis, as well as strain FB were both negative and positive gravitactic at all culture ages tested. This result confirmed the hypothesis that the paraxonemal body is not direcdy involved in graviperception.
Journal of Atmospheric and Solar-Terrestrial Physics, 2015
ABSTRACT Space radiation has been monitored using the РД3-Б3 (in the following we use the Latin t... more ABSTRACT Space radiation has been monitored using the РД3-Б3 (in the following we use the Latin transcription RD3-B3) spectrometer-dosimeter on board a recent space flight of the Russian recoverable satellite “BION-M” No. 1. The instrument was mounted inside the satellite in a pressurized volume together with biological objects and samples. The RD3-B3 instrument is a battery operated version of the spare model of the R3D-B3 instrument developed and built for the ESA BIOPAN-6 facility on Foton M3 satellite launched on September 2007 (Häder et al., 2009). It is a low mass, small dimension automated device that measures solar radiation in four channels and ionizing radiation in 256 channels of a Liulin-type energy deposition spectrometer (Dachev et al., 2002). 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. The paper summarizes the results for the Earth radiation environment at the altitude of 253-585 km.
Life Sciences in Space Research, 2015
ABSTRACT Ionizing radiation is recognized to be one of the main health concerns for humans in the... more ABSTRACT Ionizing radiation is recognized to be one of the main health concerns for humans in the space radiation environment. Estimation of space radiation effects on health requires in accurate knowledge of the accumulated absorbed dose, which depends on the global space radiation distribution, solar cycle and local shielding generated by the 3D mass distribution of the space vehicle. This paper presents an overview of the spectrometer-dosimeters of the Liulin type, which were developed in the late 1980s and have been in use since then. Two major measurement systems have been developed by our team. The first one is based on one silicon detector and is known as a Liulin-type Deposited Energy Spectrometer (DES) (Dachev et al., 2002 and 2003), while the second one is a dosimetric telescope (DT) with two or three silicon detectors. The Liulin-type instruments were calibrated using a number of radioactive sources and particle accelerators. The main results of the calibrations are presented in the paper. In the last section of the paper some of the most significant scientific results obtained in space and on aircraft, balloon and rocket flights since 1989 are presented.
Microgravity science and technology, 1997
Euglena gracilis, a unicellular photosynthetic flagellate, serves as a model system in signal tra... more Euglena gracilis, a unicellular photosynthetic flagellate, serves as a model system in signal transduction research. To further study its complex gravitaxis, experiments under microgravity are desirable. In preparation for long-term experiments on a space station, an autonomous cultivation unit has been developed and the culture conditions and surveillance methods have been established. The running time of more than 600 d under closed conditions with light as the only source of energy confirmed the stability of the Euglena population and gave new insights into its behavior. Physicochemical parameters such as oxygen concentration, temperature and pH as well as physiological parameters including cell density, motility, gravitactic orientation and pigmentation were recorded on a frequent basis. The suitability of the botanical bioreaction to serve as an oxygen supplier for animals in a closed system was demonstrated.
Life Sciences in Space Research, 2015
In recent times Euglena gracilis Z was employed as primary producer in closed environmental lifes... more In recent times Euglena gracilis Z was employed as primary producer in closed environmental lifesupport 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 Nsource in the lab (provided as diammonium-dihydrogenphosphate, (NH 4) 2 HPO 4) 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 NH 4 + (low toxicity) to be partially transformed into the highly toxic ammonia, NH 3. In earlier reports, Euglena gracilis was described to grow with various amino acids as sole N-source. Our aim was to investigate alternatives for (NH 4) 2 HPO 4 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 (NH 4) 2 HPO 4 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 (NH 4) 2 HPO 4 .
Photochemistry and Photobiology, 1998
The unicellular flagellate Euglena gracilis shows positive phototaxis at low fluence rates (510 W... more The unicellular flagellate Euglena gracilis shows positive phototaxis at low fluence rates (510 W m-2) and negative phototaxis at high fluence rates (2100 W m-2). Currently, retinal or flavidpterins are discussed as chromophores of the photoreceptor. When grown in the presence of 4 mM nicotine, a retinal inhibitor, for several generations, the cells still showed both responses, indicating that retinal is unlikely to be the chromophoric group of the photoreceptor responsible for phototaxis. The native flavin(s) can be substituted by growing the cells in roseoflavin dissolved in the medium. The absorption spectrum of roseoflavin extends well beyond the action spectrum for phototaxis (up to 600 nm). Excitation at wavelengths >550 nm does not cause phototactic orientation in control cells but causes both positive and negative phototaxis in roseoflavin-grown cells, indicating an uptake and assembly of the chromophore in the photoreceptor complex. The white mutant strain 122&5/1f, induced by streptomycin treatment, lacks flavins as indicated by fluorescence spectroscopy. The phototaxis-deficient phenotype cannot be complemented by the addition of external riboflavin. Fluorescence spectra of intact paraxonemal bodies (PAB) indicate that both pterins and flavins are involved in photoperception and that the excitation energy is efficiently funneled from the pterins to the flavins. This energy transfer is disrupted by solubilization of the PAB. In intact PAB flavins are not accessible to reducing or oxidizing substances, indicating that they are located inside the structure, while pterins are accessible, so that their localization can be assumed to be on the surface. The results described above are discussed with regard to the potential involvement of flavins and pterins as well as retinal in photoperception.
Photochemistry and Photobiology, 1985
A hardware and software system is described which is capable of automatically following the movem... more A hardware and software system is described which is capable of automatically following the movement of microorganisms and analyzing the deviation of individuals in a population from a predefined direction. The image of the moving organisms is viewed by a video camera, digitized in real time and stored in a dedicated video memory holding 512 X 256 pixels with 64 grey levels. A microcomputer has access to this video memory via four parallel ports. The software analyzes the position of an organism selected randomly and attempts to follow its track for a predefined period of time. If successful, it calculates the direction of movement and stores the data in a file for statistical analysis. Using this system, the movement of populations of the unicellular flagellate, Euglena gracilis, in unilateral and bilateral light beams has been studied and compared with the dark behavior. When irradiated from two opposite light sources of equal fluence rates half of the population swims towards either light source. However, when the light sources are oriented at an angle of 90" to each other the cells move on the resultant away from the light. These results confirm the shading hypothesis for negative phototaxis.
Botanica Acta, 1995
The effects of UV (280–400 nm) irradiation on phycobiliprotein composition have been studied in t... more The effects of UV (280–400 nm) irradiation on phycobiliprotein composition have been studied in two N2-fixing cyanobacteria, Anabaena sp. and Nostoc carmium, isolated from rice paddy fields in India. Phycobiliproteins were isolated and separated by sucrose density gradient centrifugation. After UV exposure the top fraction mainly contained carotenoids (absorption maximum at 485 nm), which first showed an increase in intensity and absorption and then a gradual decrease with increasing UV exposure in Anabaena sp., whereas, in Nostoc carmium this fraction showed a steady increase over the whole exposure time. The bottom fraction of both organisms mainly contained phycocyanin (absorption peak at 620 nm) which showed a steady decline in intensity, as well as absorption. Fluorescence excitation at 620 nm resulted in an emission at 650 nm which underwent a shift towards shorter wave-lengths with increasing UV-exposure time, indicating a disassembly of the phycobilisomal complex and of impaired energy transfer from accessory pigments to the reaction centers. SDS PAGE analysis of the fractions revealed a loss of high molecular mass linker proteins and low molecular mass (αβ monomers indicating that the phycobiliproteins, which function as accessory pigments for the operation of photosystem II, disassemble during UV irradiation.
Journal of Photochemistry and Photobiology B: Biology, 1997
The Erlanger flagellate test (EFT) is based on the green unicellular flagellate Euglena gracilis.... more The Erlanger flagellate test (EFT) is based on the green unicellular flagellate Euglena gracilis. The organisms are cultivated in minimal medium and used in their stationary growth phase. In order to quantify the effects of toxic substances or solar UV radiation, several ...
Journal of plant physiology, 1999
Gravitaxis in unicellular microorganisms like Euglena gracilis has been known for more than 100 y... more Gravitaxis in unicellular microorganisms like Euglena gracilis has been known for more than 100 years. The current model explains this phenomenon on the basis of a specific density difference between cell body and surrounding medium. In order to test the feasibility of the ...
Electrophoresis, 1998
Phycobiliproteins are homologous chromoproteins which constitute the phycobilisomes, the light ha... more Phycobiliproteins are homologous chromoproteins which constitute the phycobilisomes, the light harvesting complexes of the photosynthetic apparatus in cyanobacteria, rhodophyta and cryptophyta. In the present work, phycocyanin (PC) and phycoerythrin (PE) from a Nostoc species are proposed as protein markers for electrophoretic techniques. Phycocyanin is a blue-colored phycobiliprotein; it carries phycocyanobilin as chromophoric group and is composed of two subunits, alpha and beta, with Mr of 14000 and 17000, respectively. In contrast, the PE subunits, having a similar Mr of 21000, are deep rose chromoproteins and carry phycoerythrobilin residues. Both low molecular weight phycobiliproteins are also suitable for monitoring protein blotting and the focusing time of protein samples during isoelectric focusing as internal markers. The PE subunits which form a single broad band after sodium dodecyl sulfate-polyacrylamide gel electrophoresis have different isoelectric points, and they form two visible bands when they reach their isoelectric point. The phycobilisomes constitute up to 50% of the total protein in cyanobacteria and their content in PC or PE can be up- or down-regulated by using different light conditions (chromatic adaptation).
Astrobiology, 2013
Research in microgravity is indispensable to disclose the impact of gravity on biological process... more Research in microgravity is indispensable to disclose the impact of gravity on biological processes and organisms. However, research in the near-Earth orbit is severely constrained by the limited number of flight opportunities. Ground-based simulators of microgravity are valuable tools for preparing spaceflight experiments, but they also facilitate stand-alone studies and thus provide additional and cost-efficient platforms for gravitational research. The various microgravity simulators that are frequently used by gravitational biologists are based on different physical principles. This comparative study gives an overview of the most frequently used microgravity simulators and demonstrates their individual capacities and limitations. The range of applicability of the various ground-based microgravity simulators for biological specimens was carefully evaluated by using organisms that have been studied extensively under the conditions of real microgravity in space. In addition, current heterogeneous terminology is discussed critically, and recommendations are given for appropriate selection of adequate simulators and consistent use of nomenclature.
Journal of plant physiology, 1997
Euglena gracilis, a unicellular, photosynthetic flagellate, orients itself by means of gravi- and... more Euglena gracilis, a unicellular, photosynthetic flagellate, orients itself by means of gravi- and phototaxis to reach and stay in regions optimal for survival and growth. An improved version of the slow rotating centrifuge microscope, NIZEMI, was used to test wild type and mutant strains for their responses to hypergravity. Wild type cells could actively move against the acceleration vector up to 8.5 gn and were centrifuged down at higher rates. Even at 10.5 gn, the highest value tested, cells were still negative gravitactically oriented as shown by video images. In contrast, all mutant strains as well as Astasia longa, a close relative of Euglena, could move against the acceleration vector under all conditions tested. With increasing accelerations the mean orientation of the populations shifted according to a vectorial addition of gravity and acceleration. The r-value, a statistical measure of the orientation of a population, increased with moderately increased acceleration rates a...
Euglena gracilis, a unicellular photosynthetic flagellate, serves as a model system in signal tra... more Euglena gracilis, a unicellular photosynthetic flagellate, serves as a model system in signal transduction research. To further study its complex gravitaxis, experiments under microgravity are desirable. In preparation for long-term experiments on a space station, an autonomous cultivation unit has been developed and the culture conditions and surveillance methods have been established. The running time of more than 600 d under closed conditions with light as the only source of energy confirmed the stability of the Euglena population and gave new insights into its behavior. Physicochemical parameters such as oxygen concentration, temperature and pH as well as physiological parameters including cell density, motility, gravitactic orientation and pigmentation were recorded on a frequent basis. The suitability of the botanical bioreaction to serve as an oxygen supplier for animals in a closed system was demonstrated.
International Journal of Molecular Sciences
All life forms have evolved under the constant force of gravity on Earth and developed ways to co... more All life forms have evolved under the constant force of gravity on Earth and developed ways to counterbalance acceleration load. In space, shear forces, buoyance-driven convection, and hydrostatic pressure are nullified or strongly reduced. When subjected to microgravity in space, the equilibrium between cell architecture and the external force is disturbed, resulting in changes at the cellular and sub-cellular levels (e.g., cytoskeleton, signal transduction, membrane permeability, etc.). Cosmic radiation also poses great health risks to astronauts because it has high linear energy transfer values that evoke complex DNA and other cellular damage. Space environmental conditions have been shown to influence apoptosis in various cell types. Apoptosis has important functions in morphogenesis, organ development, and wound healing. This review provides an overview of microgravity research platforms and apoptosis. The sections summarize the current knowledge of the impact of microgravity a...
Microorganisms
Due to the increasing development of antibiotic resistances in recent years, scientists search in... more Due to the increasing development of antibiotic resistances in recent years, scientists search intensely for new methods to control bacteria. Photodynamic treatment with porphyrins such as chlorophyll derivatives is one of the most promising methods to handle bacterial infestation, but their use is dependent on illumination and they seem to be more effective against Gram-positive bacteria than against Gram-negatives. In this study, we tested chlorophyllin against three bacterial model strains, the Gram-positive Bacillus subtilis 168, the Gram-negative Escherichia coli DH5α and E. coli strain NR698 which has a deficient outer membrane, simulating a Gram-negative “without” its outer membrane. Illuminated with a standardized light intensity of 12 mW/cm2, B. subtilis showed high sensitivity already at low chlorophyllin concentrations (≤105 cfu/mL: ≤0.1 mg/L, 106–108 cfu/mL: 0.5 mg/L), whereas E. coli DH5α was less sensitive (≤105 cfu/mL: 2.5 mg/L, 106 cfu/mL: 5 mg/L, 107–108 cfu/mL: ine...
Journal of Plant Physiology, 1999
Gravitaxis in unicellular microorganisms like Euglena gracilis has been known for more than 100 y... more Gravitaxis in unicellular microorganisms like Euglena gracilis has been known for more than 100 years. The current model explains this phenomenon on the basis of a specific densiry difference berween cell body and surrounding medium. In order to test the feasibiliry of the current model in terms of physical * Correspondence.
Journal of Photochemistry and Photobiology B: Biology, 2000
A network of three channel dosimeters has been installed in Europe and other continents to contin... more A network of three channel dosimeters has been installed in Europe and other continents to continuously and automatically monitor solar radiation in the UV-B (280 – 315 nm), UV-A (315 – 400 nm) and PAR (photosynthetic active radiation, 400 – 700 nm) wavelength ranges to follow long-term and short-term changes in the light climate. The instruments are housed in rugged cases to withstand extreme environments from the polar circle to the tropics. The entrance optic is based on an integrating sphere and the wavelength selection is done by appropriate filter and photodiode combinations. Software packages have been developed to poll the data, display them graphically and store them. Quality control is warranted by careful and frequent calibration of the instruments as well as national and international intercalibrations. The data are sent to a central server in Pisa from where they can be downloaded on the Internet free of charge. The network has been in operation for the last five years and has constantly been growing in numbers. The data are being used to extract important information on changing light climate conditions and the development of stratospheric ozone.
Journal of Plant Physiology, 1997
Three mutant strains of the phytoflagellate Euglena gracilis Z have been characterized in order t... more Three mutant strains of the phytoflagellate Euglena gracilis Z have been characterized in order to analyze the signal perception and signal transduction pathways involved in photo-and gravitaxis. Using the fluorescence of the chromophoric groups believed to be involved in photoperception (flavins and pterins) a method was developed for an in situ and in vivo detection of the paraxonemal body, the proposed location of the photoreceptor molecules. Two of the mutant strains, 1224-5/9f and 1224-511f, do not possess a stigma and also lack a paraxonemal body, as indicated by fluorescence measurements. The third strain, FB, has a small stigma, but only some cells contain a paraxonemal body. In contrast to the present hypothesis on photoorientation of Euglena, all strains were able to orient with respect to the light direction. However, the mutant strains did not show any orientation at low irradiances. At medium and high irradiances the strains 1224-5/9f and 1224-5I1f oriented perpendicular to the light direction (diaphototaxis) while cells of strain FB showed partly negative phototaxis and partly diaphototaxis. Diaphototaxis was never observed in the wild type strain. Strains 1224-5/9f and 1224-511f showed normal graviresponses compared with the wild type. Astasia tonga, a nonphototactic relative of E. gracilis, as well as strain FB were both negative and positive gravitactic at all culture ages tested. This result confirmed the hypothesis that the paraxonemal body is not direcdy involved in graviperception.
Journal of Atmospheric and Solar-Terrestrial Physics, 2015
ABSTRACT Space radiation has been monitored using the РД3-Б3 (in the following we use the Latin t... more ABSTRACT Space radiation has been monitored using the РД3-Б3 (in the following we use the Latin transcription RD3-B3) spectrometer-dosimeter on board a recent space flight of the Russian recoverable satellite “BION-M” No. 1. The instrument was mounted inside the satellite in a pressurized volume together with biological objects and samples. The RD3-B3 instrument is a battery operated version of the spare model of the R3D-B3 instrument developed and built for the ESA BIOPAN-6 facility on Foton M3 satellite launched on September 2007 (Häder et al., 2009). It is a low mass, small dimension automated device that measures solar radiation in four channels and ionizing radiation in 256 channels of a Liulin-type energy deposition spectrometer (Dachev et al., 2002). 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. The paper summarizes the results for the Earth radiation environment at the altitude of 253-585 km.
Life Sciences in Space Research, 2015
ABSTRACT Ionizing radiation is recognized to be one of the main health concerns for humans in the... more ABSTRACT Ionizing radiation is recognized to be one of the main health concerns for humans in the space radiation environment. Estimation of space radiation effects on health requires in accurate knowledge of the accumulated absorbed dose, which depends on the global space radiation distribution, solar cycle and local shielding generated by the 3D mass distribution of the space vehicle. This paper presents an overview of the spectrometer-dosimeters of the Liulin type, which were developed in the late 1980s and have been in use since then. Two major measurement systems have been developed by our team. The first one is based on one silicon detector and is known as a Liulin-type Deposited Energy Spectrometer (DES) (Dachev et al., 2002 and 2003), while the second one is a dosimetric telescope (DT) with two or three silicon detectors. The Liulin-type instruments were calibrated using a number of radioactive sources and particle accelerators. The main results of the calibrations are presented in the paper. In the last section of the paper some of the most significant scientific results obtained in space and on aircraft, balloon and rocket flights since 1989 are presented.
Microgravity science and technology, 1997
Euglena gracilis, a unicellular photosynthetic flagellate, serves as a model system in signal tra... more Euglena gracilis, a unicellular photosynthetic flagellate, serves as a model system in signal transduction research. To further study its complex gravitaxis, experiments under microgravity are desirable. In preparation for long-term experiments on a space station, an autonomous cultivation unit has been developed and the culture conditions and surveillance methods have been established. The running time of more than 600 d under closed conditions with light as the only source of energy confirmed the stability of the Euglena population and gave new insights into its behavior. Physicochemical parameters such as oxygen concentration, temperature and pH as well as physiological parameters including cell density, motility, gravitactic orientation and pigmentation were recorded on a frequent basis. The suitability of the botanical bioreaction to serve as an oxygen supplier for animals in a closed system was demonstrated.