Häder D P, Rosum A, Schäfer J, Hemmersbach R
Institut für Botanik and Pharmazeutische Biologie der Friedrich-Alexander-Universität, Erlangen, Germany.
J Biotechnol. 1996 Jun 27;47(2-3):261-9. doi: 10.1016/0168-1656(96)01374-0.
During a recent space flight, gravitaxis of the unicellular photosynthetic flagellate, Euglena gracilis, was studied on board of the American shuttle Columbia. Accelerations were varied between 0 and 1.5 x g using a slow rotating centrifuge microscope (NIZEMI). The cells showed a sigmoidal response curve for the dependence of the precision of gravitaxis on acceleration which is indicative of the involvement of an active, physiological gravireceptor with a threshold at g-values < or = 0.16 x g and a saturation at g-values > or = 1 x g. No adaptation to microgravity was found during the prolonged space mission. After return the cells showed a normal gravitactic behavior at 1 x g. Since the cells are heavier than water, their swimming velocity is affected by sedimentation. The velocity distribution at different accelerations closely follows Stokes' law for sedimentation indicating that, in contrast to the ciliate Paramecium, E. gracilis, does not show any gravikinesis.
在最近一次太空飞行中，对单细胞光合鞭毛虫纤细裸藻的重力趋性进行了研究，实验是在美国航天飞机“哥伦比亚号”上进行的。使用慢速旋转离心机显微镜（NIZEMI）使加速度在0至1.5倍重力之间变化。细胞显示出重力趋性精度对加速度的依赖呈S形响应曲线，这表明存在一种活跃的生理重力感受器，其阈值在重力值≤0.16倍重力时，在重力值≥1倍重力时达到饱和。在长时间的太空任务中未发现对微重力的适应情况。返回后，细胞在1倍重力下表现出正常的重力趋性行为。由于细胞比水重，它们的游动速度会受到沉降的影响。不同加速度下的速度分布紧密遵循斯托克斯沉降定律，这表明与纤毛虫草履虫不同，纤细裸藻没有表现出任何重力运动反应。
