From Newsgroup: sci.bio.paleontology

Archaean green-light environments drove the evolution of cyanobacteriarCOs light-harvesting system

Abstract
Cyanobacteria induced the great oxidation event around 2.4rCebillion years ago, probably triggering the rise in aerobic biodiversity. While
chlorophylls are universal pigments used by all phototrophic organisms, cyanobacteria use additional pigments called phycobilins for their light-harvesting antennasrCophycobilisomesrCoto absorb light energy at complementary wavelengths to chlorophylls. Nonetheless, an enigma
persists: why did cyanobacteria need phycobilisomes? Here, we
demonstrate through numerical simulations that the underwater light
spectrum during the Archaean era was probably predominantly green owing
to oxidized Fe(III) precipitation. The green-light environments,
probably shaped by photosynthetic organisms, may have directed their own photosynthetic evolution. Genetic engineering of extant cyanobacteria, simulating past natural selection, suggests that cyanobacteria that
acquired a green-specialized phycobilin called phycoerythrobilin could
have flourished under green-light environments. Phylogenetic analyses
indicate that the common ancestor of modern cyanobacteria embraced all
key components of phycobilisomes to establish an intricate energy
transfer mechanism towards chlorophylls using green light and thus
gained strong selective advantage under green-light conditions. Our
findings highlight the co-evolutionary relationship between oxygenic phototrophs and light environments that defined the aquatic landscape of
the Archaean Earth and envision the green colour as a sign of the
distinct evolutionary stage of inhabited planets.

https://www.nature.com/articles/s41559-025-02637-3. (Open access)
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