Researchers from the University of Liverpool have unveiled intricate details of the key photosynthetic protein complexes in purple bacteria, shedding new light on how these microorganisms harness solar energy. This breakthrough has potential applications in the development of artificial photosynthetic systems for clean energy production. The study delves into the structural diversity of photosynthetic complexes, even among closely related bacterial species, and how this variability reflects evolutionary adaptations to specific environmental conditions. Photosynthesis and bacterial biology are crucial to understanding the evolution of life on Earth and the nutrient cycles that sustain our ecosystems.
Deciphering the Complex Architecture in Photosystem I
The work appears in Science Advances, where the authors reveal high-resolution structures of a photosynthetic reaction center–light-harvesting complexes (RC-LH1) from Rhodobacter blasticus, an organism commonly used to investigate bacterial photosynthesis. The research team, led by Professor Luning Liu from the University of Liverpool, along with collaborators at Ocean University of China, Huazhong Agricultural University and Thermo Fisher Scientific, imaged both monomeric and dimeric forms of the RC-LH1 membrane protein supercomplexes in a bacterium.
These structures possess attributes, which can be seen in no other group of organisms using these specific configurations for photosynthesis, and they underline the vast range possible within the purple bacteria sensu stricto. R. blasticus differs significantly from other commonly used model species in having a much flatter RC-LH1 dimer structure. The basis of this structure is essential for certain membrane curvature and energy transfer efficiency in bacteria.
Finding the Evolution of Deadly Photosynthesis in Bacteria
Despite great similarities in organization and chromatic adaptation of the RC-LH1 complex with that from other related bacteria, proteins analogous to PufY protein are absent in the structure made by R. blasticus. The absence of PufX is complemented by other light-harvesting subunits that pack around LHI to form a more closed LH1 ring. This structural change was suggested to modulate the electron transport rates of the RC-LH1 complex, demonstrating how bacteria are able to adapt their photosynthetic machinery for a given environmental situation.
According to Liu, the fact that this project is systematic combining structural biology with in silico simulations and spectroscopy to study how bacterial photosynthetic complexes are assembled and how they mediate electron transfer — both of which are pivotal processes for energy production. Our findings reveal a broad spectrum of structural variation in photosynthetic complexes, even across closely related bacterial species. That variability is probably representative of evolutionary adaptations to particular environmental conditions,” he said.
Decarbonizing the economy with clean energy innovation
As well as pushing the field of bacterial photosynthesis research further, this new study could help determine how to create artificial, synthetic systems that mimic the behavior of their natural counterparts in sunlight to produce clean sources of energy. This ability to see the natural methods of photosynthesis used by bacteria allows new pathways to design more effective light-harvesting and energy transducing systems or cells, as reported in Scientific Reports.
Professor Liu said: “We are very excited that, from the perspective of molecular biology, we can reveal details on artificial photosynthesis and its evolution. “By learning how bacteria tailor their photosynthetic machinery, we can create better bio-inspired technologies to move closer to a more sustainable future,” Taga said.
