Investigation of Gravitaxis and Phototaxis in Euglena gracilis

Häder DP, Faddoul J, Lebert M, Richter P, Schuster M, Richter R, Strauch S, Daiker V (2010)

Publication Type: Book chapter / Article in edited volumes

Publication year: 2010

Publisher: I. K. International Publishing House Pvt. Ltd.

Edited Volumes: Advances in Life Sciences

Pages Range: 117-131


This article provides an overview of the research of phototaxis and gravitaxis in the unicellular flagellate Euglena gracilis. The cells show positive phototaxis at low light intensities (swimming towards the light source, below 10 W/m2, sunlight) and a negative one upon high irradiances (>10 W/m2). Phototaxis is based on a blue light-activated adenylyl cyclase, which produces cAMP upon irradiation. The further steps following the transient rise of the cAMP concentration are still unknown. Gravitaxis is a movement parallel to an acceleration vector. In the absence of external stimuli the cells swim upward in the water column (negative gravitaxis), upon stress gravitaxis inverts into a positive one. The results of sounding rocket campaigns and of a large number of ground experiments led to the following model of signal perception and transduction in gravitaxis of Euglena gracilis: The body of the cell is heavier than the surrounding medium, sediments and thereby exerts a force onto the lower membrane. Upon deviation from a vertical swimming path mechano-sensitive elements are activated. This leads to an increase in the intracellular calcium concentration and a change of the membrane potential. The increased calcium concentration regulates the action of calmodulin, which in turn modulates an adenylyl cyclase, which converts ATP to cAMP. cAMP probably controls the flagellar beat and/or probably the shape of the cell. Phototaxis as well as gravitaxis are probably controlled by certain protein kinases. The blockage of different protein kinases (PK) by means of RNAi gave rise to the assumption that both signal pathways activate certain PKs. The blockage of one PK resulted in a loss of gravitaxis, the blockage of another one in loss of phototactic behaviour.

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Häder, D.-P., Faddoul, J., Lebert, M., Richter, P., Schuster, M., Richter, R.,... Daiker, V. (2010). Investigation of Gravitaxis and Phototaxis in Euglena gracilis. In R. P. Sinha, N.K. Sharma, A.K. Rai (Eds.), Advances in Life Sciences. (pp. 117-131). I. K. International Publishing House Pvt. Ltd..


Häder, Donat-Peter, et al. "Investigation of Gravitaxis and Phototaxis in Euglena gracilis." Advances in Life Sciences. Ed. R. P. Sinha, N.K. Sharma, A.K. Rai, I. K. International Publishing House Pvt. Ltd., 2010. 117-131.

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