Maria Ntefidou

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Euglena gracilis, a unicellular freshwater protist exhibits different photomovement responses, such as phototaxis (oriented movement toward or away from the light source) and photophobic (abrupt turn in response to a rapid increase [step-up] or decrease [step-down] in the light fluence rate) responses. Photoactivated adenylyl cyclase (PAC) has been isolated(More)
Anabaena sensory rhodopsin (ASR) is a novel microbial rhodopsin recently discovered in the freshwater cyanobacterium Anabaena sp. PCC7120. This protein most likely functions as a photosensory receptor as do the related haloarchaeal sensory rhodopsins. However, unlike the archaeal pigments, which are tightly bound to their cognate membrane-embedded(More)
Channelrhodopsins act as photoreceptors for control of motility behavior in flagellates and are widely used as genetically targeted tools to optically manipulate the membrane potential of specific cell populations ("optogenetics"). The first two channelrhodopsins were obtained from the model organism Chlamydomonas reinhardtii (CrChR1 and CrChR2). By(More)
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(More)
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(More)
In the absence of other external stimuli the motile, unicellular freshwater flagellate Euglena gracilis normally swims upward in the water column (negative gravitaxis). This behavior is most likely triggered by active physiological orientation mechanisms. Recently it was found that negative gravitaxis often inverts to a positive one upon high light(More)
The unicellular, green flagellate wild-type Euglena gracilis(strain Z) and its colorless phototaxis-mutant strains as well as the non-photosynthetic close relative, Astasia longa, possess several genes of the photoactivated adenylyl cyclase (PAC) family. The corresponding gene products were found to be responsible for step-up (but not step-down) photophobic(More)
There is strong evidence that gravitactic orientation in flagellates and ciliates is mediated by an active physiological gravireceptor rather than by passive alignment of the cells in the water column. In flagellates the threshold for graviorientation was found to be at 0.12 x g on a slow rotating centrifuge during the IML-2 mission on the Shuttle Columbia(More)
To meet the todays needs for the protection of the environment from pollution through cumulative poisonings or biohazards ecotoxicology uses biotests, to determine effects of chemicals and sewage waters to ecosystems. ECOTOX is a biotest system that allows both the estimation of risks arising from certain substances or substance mixtures as well as the(More)