Six Christophe, Finkel Zoe V, Irwin Andrew J, Campbell Douglas A
Mount Allison University, Sackville, New Brunswick, Canada.
PLoS One. 2007 Dec 19;2(12):e1341. doi: 10.1371/journal.pone.0001341.
Prochlorococcus and Synechococcus picocyanobacteria are dominant contributors to marine primary production over large areas of the ocean. Phytoplankton cells are entrained in the water column and are thus often exposed to rapid changes in irradiance within the upper mixed layer of the ocean. An upward fluctuation in irradiance can result in photosystem II photoinactivation exceeding counteracting repair rates through protein turnover, thereby leading to net photoinhibition of primary productivity, and potentially cell death. Here we show that the effective cross-section for photosystem II photoinactivation is conserved across the picocyanobacteria, but that their photosystem II repair capacity and protein-specific photosystem II light capture are negatively correlated and vary widely across the strains. The differences in repair rate correspond to the light and nutrient conditions that characterize the site of origin of the Prochlorococcus and Synechococcus isolates, and determine the upward fluctuation in irradiance they can tolerate, indicating that photoinhibition due to transient high-light exposure influences their distribution in the ocean.
原绿球藻和聚球藻等蓝细菌是大洋大片区域海洋初级生产力的主要贡献者。浮游植物细胞被卷入水柱中，因此常常在海洋上层混合层内暴露于光照强度的快速变化之中。光照强度的向上波动可导致光系统II的光失活超过通过蛋白质周转的抵消修复速率，从而导致初级生产力的净光抑制，并可能导致细胞死亡。在此我们表明，光系统II光失活的有效截面在整个蓝细菌中是保守的，但它们的光系统II修复能力和蛋白质特异性光系统II光捕获能力呈负相关，且在不同菌株间差异很大。修复速率的差异与原绿球藻和聚球藻分离株起源地的光照和营养条件相对应，并决定了它们能够耐受的光照强度向上波动，这表明由于短暂高光暴露引起的光抑制影响了它们在海洋中的分布。
