Go with the flow: energetic robustness inbacterial photosynthesis
** Lecture will be given in English**
Abstract:
Photosynthetic organisms, such as cyanobacteria and purplebacteria, optimize solar energy conversion with high efficiency despitefluctuating environmental conditions. Cyanobacteria utilize large PSI-IsiAsuper complexes to sustain themselves under bioavailable iron scarcity. Wefound that the Cryo-EM structure of PSI-IsiA from Synechocystis PCC 6803reveals significant structural heterogeneity within the complex, yetsingle-molecule fluorescence spectroscopy experiments confirm consistent energytransfer efficiency. This efficiency is maintained or even enhanced in certainconformations through specific chlorophyll arrangements. Similarly, purplebacteria employ chromatic acclimation to tune their photosynthetic machineryunder low-light conditions, replacing LH2 to LH3 antenna complexes, havingdifferent protein-chromophore interactions to manage spectral tuning. We showhow this is achieved using cryo-EM, and provide evidence for the uniqueenergetic dynamic of the Rbl. acidophilus 7750 strain using ultrafast transientabsorption spectroscopy. This unique dynamic is achieved thanks to a specificgeometry allowing uphill energy transfer between absorption bands. Both systemsdemonstrate mechanisms where sophisticated design support robust energy transfer,suggesting a common theme in photosynthetic organisms to mitigate the impactsof environmental changes by harness structural changes to keep high energyconversion efficiency.
