Stingaciu Laura-Roxana, O'Neill Hugh, Liberton Michelle, Urban Volker S, Pakrasi Himadri B, Ohl Michael
JCNS1, outstation at SNS, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
NScD, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
Sci Rep. 2016 Jan 21;6:19627. doi: 10.1038/srep19627.
Cyanobacteria are photosynthetic prokaryotes that make major contributions to the production of the oxygen in the Earth atmosphere. The photosynthetic machinery in cyanobacterial cells is housed in flattened membrane structures called thylakoids. The structural organization of cyanobacterial cells and the arrangement of the thylakoid membranes in response to environmental conditions have been widely investigated. However, there is limited knowledge about the internal dynamics of these membranes in terms of their flexibility and motion during the photosynthetic process. We present a direct observation of thylakoid membrane undulatory motion in vivo and show a connection between membrane mobility and photosynthetic activity. High-resolution inelastic neutron scattering experiments on the cyanobacterium Synechocystis sp. PCC 6803 assessed the flexibility of cyanobacterial thylakoid membrane sheets and the dependence of the membranes on illumination conditions. We observed softer thylakoid membranes in the dark that have three-to four fold excess mobility compared to membranes under high light conditions. Our analysis indicates that electron transfer between photosynthetic reaction centers and the associated electrochemical proton gradient across the thylakoid membrane result in a significant driving force for excess membrane dynamics. These observations provide a deeper understanding of the relationship between photosynthesis and cellular architecture.
蓝藻是光合原核生物，对地球大气中氧气的产生做出了重大贡献。蓝藻细胞中的光合机制位于称为类囊体的扁平膜结构中。蓝藻细胞的结构组织以及类囊体膜响应环境条件的排列方式已得到广泛研究。然而，关于这些膜在光合过程中的灵活性和运动方面的内部动态，了解有限。我们展示了对体内类囊体膜波动运动的直接观察，并揭示了膜流动性与光合活性之间的联系。对集胞藻PCC 6803进行的高分辨率非弹性中子散射实验评估了蓝藻类囊体膜片的柔韧性以及膜对光照条件的依赖性。我们观察到在黑暗中类囊体膜更柔软，其流动性比高光条件下的膜高出三到四倍。我们的分析表明，光合反应中心之间的电子转移以及跨类囊体膜的相关电化学质子梯度产生了显著的驱动力，导致膜出现过多动态。这些观察结果有助于更深入地理解光合作用与细胞结构之间的关系。
