Life in the dessert: how does Chlorella ohadii adapt its photosynthetic system to high-damaging light conditions?

Chlorella ohadii is a green micro-algae isolated from Biological sand crusts (BSCs) in the north-western Negev desert, Israel. BSCs are some of the harshest environments on our planet. Any organism inhabiting these extreme ecosystems is obligated to developing various adaptations to survive and reproduce in an environment that is very challenging due to extreme temperatures, long droughts and highly damaging light conditions. Since the isolation of C. ohadii some studies have revealed intriguing characteristics enabling it to thrive in these conditions; these include the fastest reported growth rate of a photosynthetic eukaryote, high light induced shifts in photosynthesis electron transfer chain configuration and astonishing resistance to photoinhibition at light intensities of up to 3500µE m-2s-1. To shed further light on the mechanisms behind C. ohadii’s remarkable resistance to photoinhibition we are investigating the photosystem (PS) of high light cultured C. ohadii using isolated thylakoid membranes. Applying different methods such as PS activity and kinetic assays, fluorescence induction, western blots, native PAGE and mass-spectrometry based proteomics has enabled us to achieve valuable results. Our work suggest the utilization of various mechanisms related to photo-protection including reduction of the light-energy absorbing antennas, biosynthesis and accumulation of carotenoids, a decrease in PSI and PSII components and overexpression of numerous photo-protection related proteins. Our research offers exciting insights of C. ohadii’s photoinhibition resistance and provides data which is highly valuable regarding various fields such as microbiology, agriculture and biotechnology.