Program     PACECS: Processes and Approaches of Coastal Ecosystem Carbon Sequestration/ MEMCS: Mechanisms and Environmental Effects of Microbes on Carbon Sequestration       Poster Synechococcus sp. PCC7002 uses sulfide: quinone oxidoreductase to tolerate sulfide and intense light P-SPS2-08-S Daixi Liu* , Shandong University, China Chuanjuan Lv, Shandong University, China Jihua Liu, Shandong University, China Luying Xun, Shandong University, China Presenter Email: liudaixi@yeah.net Ocean deoxygenation and eutrophication may occur in coastal waters, especially in areas receiving sufficient nutrients from agricultural activities. Sulfide may accumulate in the oxygen minimum zones, and it has widespread effects on marine life. Cyanobacteria are photosynthetic prokaryotes, playing a significant role in carbon fixation in the ocean. Little is known about the effects of sulfide on cyanobacteria. Here we report that Synechococcus sp. PCC7002, harboring a sqr gene encoding sulfide: quinone oxidoreductase (SQR), could survive in sulfide-rich environments, while its sqr mutant could not. Further, SQR facilitated adaption to high light intensity. Preliminary data suggested that polysulfide, the produce of sulfide oxidation by SQR, was a key component of the light adaptation, since polysulfide concentration in the wild type is twice of that in the sqr deletion mutant. Thus, SQR helps Synechococcus sp. PCC7002 to tolerate sulfide and adapt to intense light, bridging the marine C and S cycles.