Biological complexity: more photosynthesis complexity (Introduction)

by David Turell , Wednesday, July 14, 2021, 17:22 (1228 days ago) @ David Turell

New components found for low light environments:

https://phys.org/news/2021-07-unique-pigments-photosynthetic-marine-bacterium.html

"Scientists used to believe that photosystem I, the membrane protein complex present in all aerobic organisms, utilized a form of chlorophyll called chlorophyll a for photosynthesis. But that changed when a marine cyanobacterium was discovered in the 1990s that employs a different form of chlorophyll; Acaryochloris marina uses chlorophyll d to harness far-red wavelengths of light, whose energy was previously considered to be too low to be useful for typical organisms.

"'How A. marina uses low-energy light for photosynthesis has been a long-standing question," notes Koji Yonekura, who leads the Biostructural Mechanism Group at the RIKEN SPring-8 Center.

"Now, Tasuku Hamaguchi, Keisuke Kawakami, Yonekura and their colleagues have shed light on this question by analyzing the structure of the photosystem I reaction center—the part of chlorophyll that converts sunlight into a form of chemical energy that can be used by the rest of the photosynthetic machinery—of chlorophyll d in A. marina. They realized this by using cryo-electron microscopy at a higher resolution than has been applied to look at these protein complexes before.

"The researchers' analysis revealed that one of the light-harvesting pigments is pheophytin a, a metal-free chlorin that differs from other type I reaction centers. This exquisite combination of pheophytin a and chlorophyll d helps to explain some ways that the cyanobacterium can efficiently harness the low energy of far-red light for photosynthesis."

Comment: The word 'exquisite' shows how beautifully designed this system appears to be. Not by chance. The more complexity we find, the more a designer must be necessary.