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Paolo Gualtieri - One of the best experts on this subject based on the ideXlab platform.
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Anatomy of Euglena gracilis
Handbook of Algal Science Technology and Medicine, 2020Co-Authors: Laura Barsanti, Paolo GualtieriAbstract:Abstract In this review we will describe the structure of the photosynthetic unicellular alga Euglena gracilis (Euglenozoa, Euglenophyceae). The description of the cell will proceed from the outside structures to the inside components. Details will be given at both microscopic and ultra-microscopic levels citing the most recent data, only for those structures that are not comparable with analogue structures found in most algae. Special attention will be given to the peculiar features of Euglena such as pellicle, photoreceptive system, storage products, and chloroplasts. We will also analyze the swimming behavior of the cell highlighting the role of photoreception in guiding the cell movement. The importance of Euglena as a promising source of immunopotentiating compounds will be discussed.
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Euglena gracilis Case: A Real Biosensor
Molecular Electronics: Bio-sensors and Bio-computers, 2003Co-Authors: Davide Bertolini, Paolo GualtieriAbstract:For over 100 years, a major object of photobiological studies has been the unicellular flagellate, Euglena gracilis, an organism well suited for such investigations by its special complement of organelles that may be considered an ancient, yet complete “visual” system. This paper deals with the hypothesis of protein bistability oriented dipole and electroconformational coupling mechanisms as the physical phenomena that produce signal transduction. A model for phototaxis is presented.
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Morphological investigations of the Euglena gracilis isolated paraflagellar body
Micron and Microscopica Acta, 2002Co-Authors: Paolo Gualtieri, Vincenzo Passarelli, Laura Barsanti, Franco VerniAbstract:Abstract By means of scanning electron microscopy we have investigated the morphology of the photoreceptive-locomotory apparatus of the flagellate Euglena gracilis . As can be seen from the micrographs, there is a strong connection between the paraflagellar rod and the paraflagellar body; structural and functional details are discussed, and a simple model of the photoreceptive apparatus is given.
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The photoreceptor protein of Euglena gracilis
FEBS Letters, 2000Co-Authors: Laura Barsanti, Vincenzo Passarelli, Patricia L. Walne, Paolo GualtieriAbstract:We isolated the photoactive protein Erh, isolated from the photoreceptor of the unicellular photosynthetic flagellate Euglena gracilis. It is a 27 kDa protein with a photocycle resembling that of sensory rhodopsin, but with at least one stable intermediate. We recorded the absorption spectrum of the parent form of this protein both under native form and in the presence of hydroxylamine and sodium borohydride, and the fluorescence spectra of both the parent and intermediate forms. We suggest that Erh is a rhodopsin-like protein and propose a simple photocycle. This protein shows optical bistability, without thermal deactivation.
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The photoreceptor protein of Euglena gracilis
FEBS Letters, 2000Co-Authors: Laura Barsanti, Vincenzo Passarelli, Patricia L. Walne, Paolo GualtieriAbstract:We isolated the photoactive protein Erh, isolated from the photoreceptor of the unicellular photosynthetic flagellate Euglena gracilis. It is a 27 kDa protein with a photocycle resembling that of sensory rhodopsin, but with at least one stable intermediate. We recorded the absorption spectrum of the parent form of this protein both under native form and in the presence of hydroxylamine and sodium borohydride, and the fluorescence spectra of both the parent and intermediate forms. We suggest that Erh is a rhodopsin-like protein and propose a simple photocycle. This protein shows optical bistability, without thermal deactivation.
Peter Richter - One of the best experts on this subject based on the ideXlab platform.
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amino acids as possible alternative nitrogen source for growth of Euglena gracilis z in life support systems
Life sciences in space research, 2015Co-Authors: Peter Richter, Yanjun An, Xugang Li, Adeel Nasir, Sebastian M Strauch, Ina Becker, Martin Schuster, Julia Krüger, Maria Ntefidou, Viktor DaikerAbstract:Abstract 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, (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 .
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Physiological characterization of gravitaxis in Euglena gracilis.
Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology, 2002Co-Authors: Peter Richter, Christine Streb, Michael Lebert, Maria Ntefidou, Donat-peter HäderAbstract:The motile, unicellular freshwater flagellate Euglena gracilis uses external stimuli, like gravity, light or oxygen pressure in order to orient itself in its natural habitat. In the darkness the cells normally show a negative gravitactic behavior, that means they swim upward in the water column, Many ground and space experiment revealed that gravitaxis is most likely based on active physiological mechanisms (involvement of calcium, cAMP, membrane potential and other parameters).
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Sensory transduction of gravitaxis in Euglena gracilis
Journal of Plant Physiology, 2002Co-Authors: Christine Streb, Peter Richter, Michael Lebert, Maria Ntefidou, Donat-peter HäderAbstract:Summary Euglena gracilis is a single-celled freshwater flagellate which shows, among other movement behaviors, a negative gravitaxis (cells swim upward in the water column) and a pronounced phototaxis. Gravitaxis is most likely an active physiological mechanism, and the influence of various inhibitors on the gravitaxis in Euglena gracilis was tested using the fully automatic image analysis system ECOTOX to elucidate the possible cellular mechanism of gravity perception and signal transduction. Substances such as the phosphodiesterase inhibitors theophylline, IBM-X and forskolin, which increase the intracellular cAMP concentration, enhance the precision of graviorientation of the cells measured shortly after incubation. Indomethacin, which decreases the intracellular cAMP concentration by inhibition of the adenylate cyclase, inhibited graviorientation. All inhibitors of calmodulin metabolism tested reduced the precision of gravitaxis in Euglena gracilis. Heparin and LiCl, which inhibit the IP3-pathway (block IP3 channels or formation of IP3, respectively) had no effect. The potassium channel blockers BaCl2 and CsCl showed an effect on the orientation behavior, while tetraethylammonium (TEA) had no influence. The protein phosphatase inhibitor, ocadaic acid, inhibited graviorientation at low concentrations. The data are discussed with respect to the current working model for gravitaxis in Euglena gracilis
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Physical characterization of gravitaxis in Euglena gracilis.
Journal of Plant Physiology, 1999Co-Authors: Michael Lebert, Peter Richter, Markus Porst, Donat-peter HäderAbstract:Summary 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 current model in terms of physical considerations the specific density of different Euglena gracilis cultures was determined. Depending on the culture conditions the specific density was in a range between 1.046 g mL −1 and 1.054 g mL −1 . Size and gravitaxis measurements were performed in parallel, which allowed to relate the force applied to the lower membrane to the kinetic properties of gravitactic reorientation. A linear relationship between force and gravitaxis kinetics was found. A comparison between estimated activation energy of the proposed stretchsensitive ion channels and energy supplied by the displacement of the lower membrane by the sedimentation of the cell body revealed that a focussing, an amplification and/or an integration period over time must be involved in the gravitactic signal transduction chain. Analysis of stimulus-response curves revealed an integration period of about 5 seconds before a gravitactic reorientation starts. The kinetics of gravitaxis at 1 × g n and 0.12 × g n was found to be similar. A hypothesis is presented that explains this finding on the basis of a combination of an integration period and an all-or-none reaction during gravitactic reorientation.
William Martin - One of the best experts on this subject based on the ideXlab platform.
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The Mitochondrion of Euglena gracilis
Advances in Experimental Medicine and Biology, 2017Co-Authors: Verena Zimorski, Cessa Rauch, Aloysius G M Tielens, Jaap J. Van Hellemond, William MartinAbstract:In the presence of oxygen, Euglena gracilis mitochondria function much like mammalian mitochondria. Under anaerobiosis, E. gracilis mitochondria perform a malonyl-CoA independent synthesis of fatty acids leading to accumulation of wax esters, which serve as the sink for electrons stemming from glycolytic ATP synthesis and pyruvate oxidation. Some components (enzymes and cofactors) of Euglena’s anaerobic energy metabolism are found among the anaerobic mitochondria of invertebrates, others are found among hydrogenosomes, the H2-producing anaerobic mitochondria of protists.
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the mitochondrion of Euglena gracilis
Advances in Experimental Medicine and Biology, 2017Co-Authors: Verena Zimorski, Cessa Rauch, Jaap J Van Hellemond, Aloysius G M Tielens, William MartinAbstract:In the presence of oxygen, Euglena gracilis mitochondria function much like mammalian mitochondria. Under anaerobiosis, E. gracilis mitochondria perform a malonyl-CoA independent synthesis of fatty acids leading to accumulation of wax esters, which serve as the sink for electrons stemming from glycolytic ATP synthesis and pyruvate oxidation. Some components (enzymes and cofactors) of Euglena’s anaerobic energy metabolism are found among the anaerobic mitochondria of invertebrates, others are found among hydrogenosomes, the H2-producing anaerobic mitochondria of protists.
Donat-peter Häder - One of the best experts on this subject based on the ideXlab platform.
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Phototaxis Photoreceptor in Euglena gracilis
Light Sensing in Plants, 2005Co-Authors: Donat-peter Häder, Maria Ntefidou, Mineo Iseki, Masakatsu WatanabeAbstract:Many motile microorganisms, such as flagellates and ciliates, optimize their posi- tion in the water column by motile responses controlled by external stimuli. The photosynthetic, unicellular flagellate Euglena gracilis primarily uses light ([Lebert and Hader 2000], [Lebert 2001])and gravity ([Hader et al 2003]) for this purpose.
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Physiological characterization of gravitaxis in Euglena gracilis.
Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology, 2002Co-Authors: Peter Richter, Christine Streb, Michael Lebert, Maria Ntefidou, Donat-peter HäderAbstract:The motile, unicellular freshwater flagellate Euglena gracilis uses external stimuli, like gravity, light or oxygen pressure in order to orient itself in its natural habitat. In the darkness the cells normally show a negative gravitactic behavior, that means they swim upward in the water column, Many ground and space experiment revealed that gravitaxis is most likely based on active physiological mechanisms (involvement of calcium, cAMP, membrane potential and other parameters).
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Sensory transduction of gravitaxis in Euglena gracilis
Journal of Plant Physiology, 2002Co-Authors: Christine Streb, Peter Richter, Michael Lebert, Maria Ntefidou, Donat-peter HäderAbstract:Summary Euglena gracilis is a single-celled freshwater flagellate which shows, among other movement behaviors, a negative gravitaxis (cells swim upward in the water column) and a pronounced phototaxis. Gravitaxis is most likely an active physiological mechanism, and the influence of various inhibitors on the gravitaxis in Euglena gracilis was tested using the fully automatic image analysis system ECOTOX to elucidate the possible cellular mechanism of gravity perception and signal transduction. Substances such as the phosphodiesterase inhibitors theophylline, IBM-X and forskolin, which increase the intracellular cAMP concentration, enhance the precision of graviorientation of the cells measured shortly after incubation. Indomethacin, which decreases the intracellular cAMP concentration by inhibition of the adenylate cyclase, inhibited graviorientation. All inhibitors of calmodulin metabolism tested reduced the precision of gravitaxis in Euglena gracilis. Heparin and LiCl, which inhibit the IP3-pathway (block IP3 channels or formation of IP3, respectively) had no effect. The potassium channel blockers BaCl2 and CsCl showed an effect on the orientation behavior, while tetraethylammonium (TEA) had no influence. The protein phosphatase inhibitor, ocadaic acid, inhibited graviorientation at low concentrations. The data are discussed with respect to the current working model for gravitaxis in Euglena gracilis
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Physical characterization of gravitaxis in Euglena gracilis.
Journal of Plant Physiology, 1999Co-Authors: Michael Lebert, Peter Richter, Markus Porst, Donat-peter HäderAbstract:Summary 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 current model in terms of physical considerations the specific density of different Euglena gracilis cultures was determined. Depending on the culture conditions the specific density was in a range between 1.046 g mL −1 and 1.054 g mL −1 . Size and gravitaxis measurements were performed in parallel, which allowed to relate the force applied to the lower membrane to the kinetic properties of gravitactic reorientation. A linear relationship between force and gravitaxis kinetics was found. A comparison between estimated activation energy of the proposed stretchsensitive ion channels and energy supplied by the displacement of the lower membrane by the sedimentation of the cell body revealed that a focussing, an amplification and/or an integration period over time must be involved in the gravitactic signal transduction chain. Analysis of stimulus-response curves revealed an integration period of about 5 seconds before a gravitactic reorientation starts. The kinetics of gravitaxis at 1 × g n and 0.12 × g n was found to be similar. A hypothesis is presented that explains this finding on the basis of a combination of an integration period and an all-or-none reaction during gravitactic reorientation.
Aloysius G M Tielens - One of the best experts on this subject based on the ideXlab platform.
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The Mitochondrion of Euglena gracilis
Advances in Experimental Medicine and Biology, 2017Co-Authors: Verena Zimorski, Cessa Rauch, Aloysius G M Tielens, Jaap J. Van Hellemond, William MartinAbstract:In the presence of oxygen, Euglena gracilis mitochondria function much like mammalian mitochondria. Under anaerobiosis, E. gracilis mitochondria perform a malonyl-CoA independent synthesis of fatty acids leading to accumulation of wax esters, which serve as the sink for electrons stemming from glycolytic ATP synthesis and pyruvate oxidation. Some components (enzymes and cofactors) of Euglena’s anaerobic energy metabolism are found among the anaerobic mitochondria of invertebrates, others are found among hydrogenosomes, the H2-producing anaerobic mitochondria of protists.
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the mitochondrion of Euglena gracilis
Advances in Experimental Medicine and Biology, 2017Co-Authors: Verena Zimorski, Cessa Rauch, Jaap J Van Hellemond, Aloysius G M Tielens, William MartinAbstract:In the presence of oxygen, Euglena gracilis mitochondria function much like mammalian mitochondria. Under anaerobiosis, E. gracilis mitochondria perform a malonyl-CoA independent synthesis of fatty acids leading to accumulation of wax esters, which serve as the sink for electrons stemming from glycolytic ATP synthesis and pyruvate oxidation. Some components (enzymes and cofactors) of Euglena’s anaerobic energy metabolism are found among the anaerobic mitochondria of invertebrates, others are found among hydrogenosomes, the H2-producing anaerobic mitochondria of protists.