Linking the emergence of oxygenic photosynthesis to geological evolution of Earth.

What is it about?

While the impact of the emergence of oxygenic photosynthesis is most evident in the GOE at 2.4 billion years ago, there is a wealth of evidence indicating that it emerged much earlier in the Archaean era. Moreover, phylogenetic evidence suggests that the process emerged first in a freshwater environment considerably earlier than the GOE. There is growing evidence that the Earth was effectively an ocean-planet until the late Archaean, with little dry land. However, improvements in oxygen (and other) isotopic measurements now suggest that from 3.2 billion years ago until the GOE, continental crust progressively emerged from the oceans, expanding the habitats in which aquatic cyanobacteria could thrive. Our article links the phylogenetic evidence to the geological evidence, providing a strong case for the emergence of continental crust as a requirement for oxygenation - but as a result of the expansion in the number of available habitats for cyanobacteria. Finally, we suggest an explanation for the appearance of anoxygenic photosynthetic bacterial species in formerly aerobic heterotrophic lineages. We suggest that increased volcanic outgassing in the Paleoproterozoic era generated niches in which there was suitable selective pressure for formerly aerobic bacteria to acquire and maintain photosynthetic activities.

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Why is it important?

This article is the first to link the expansion and subsequent evolution of photosynthesis to the changing geological environment in which these processes originated.

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