Burriesci Matthew, Bhaya Devaki
Department of Plant Biology, The Carnegie Institution, 260 Panama Street, Stanford, CA 94305, United States.
J Photochem Photobiol B. 2008 May 29;91(2-3):77-86. doi: 10.1016/j.jphotobiol.2008.01.012. Epub 2008 Feb 13.
The unicellular cyanobacterium Synechocystis sp. Strain PCC 6,803 exhibits phototaxis by moving along a surface towards a light source. This process requires Type IV pili and a phytochrome-like photoreceptor coupled to a complex signal transduction pathway. Cells progress through different phases of interaction before the development of finger-like projections moving in the direction of the light that are characteristic of phototaxis. To probe the interaction between individual cells during the initial phase of phototaxis we tracked and analyzed a large number of cells. We observed that individual cells have limited motility, but when cells divide and/or aggregate to attain a certain minimal group size, enhanced motility and phototaxis is observed. At the later stages of motility, there is noticeable phototactic behavior which results in the appearance of the finger-like projections. Our results indicate that cells prefer to move over areas previously traversed by other cells and confine themselves to these areas and that cells alter local surface characteristics allowing for enhanced motility. Based on cell tracking data we present a preliminary random walk model showing the forces that might interact to create the typical phases of phototaxis and motility. In this model, we can simulate the formation of finger-like projections that are characteristic of phototaxis.
单细胞蓝藻聚球藻属6803菌株通过沿表面朝着光源移动来表现出趋光性。这个过程需要IV型菌毛和一种与复杂信号转导途径偶联的类光敏色素光感受器。在形成朝着光的方向移动的指状突起（趋光性的特征）之前，细胞会经历不同的相互作用阶段。为了探究趋光性初始阶段单个细胞之间的相互作用，我们追踪并分析了大量细胞。我们观察到单个细胞的运动能力有限，但当细胞分裂和/或聚集达到一定的最小群体大小时，就会观察到增强的运动能力和趋光性。在运动的后期阶段，会出现明显的趋光行为，导致指状突起的出现。我们的结果表明，细胞更喜欢在其他细胞先前走过的区域移动，并将自身限制在这些区域，并且细胞会改变局部表面特征以增强运动能力。基于细胞追踪数据，我们提出了一个初步的随机游走模型，展示了可能相互作用以产生趋光性和运动典型阶段的力。在这个模型中，我们可以模拟趋光性特征的指状突起的形成。
