2. Prof. Nir Keren

High light and dehydration are a combination of stress conditions that is relevant to all terrestrial photosynthetic organisms, in both natural and manmade habitats.  However, among photosynthetic organisms there is only a small group that can effectively counteract these stresses.  These microorganisms make their home in some of the harshest, most fluctuating, terrestrial environments; including deserts, intertidal zones, and exposed rock surfaces. In my talk I will focus on the adaptation of the photosynthetic apparatus to these conditions. Our work focuses on the adaptation and acclimation of the cyanobacterial photosynthetic apparatus to hydration/desiccation cycles. We have evidence for a number of mechanisms that allow desert cyanobacteria to shut down photosynthesis when desiccated and immediately restore it when hydrated. These mechanisms function on the level of exciton energy and electron transport. Using spectroscopic techniques, we can follow the initiation of these processes with the progression of desiccation.