Without Oxygen, Earth's Early Microbes Relied on Arsenic to Sustain Life
Phoenix666 writes:
A key component of the oxygen cycle is where plants and some types of bacteria essentially take sunlight, water, and CO2, and convert them to carbohydrates and oxygen, which are then cycled and used by other organisms that breathe oxygen. This oxygen serves as a vehicle for electrons, gaining and donating electrons as it powers through the metabolic processes. However, for half of the time life has existed on Earth, there was no oxygen present
[...] Visscher explains, "We started working in Chile, where I found a blood red river. The red sediments are made up by anoxogenic photosynthetic bacteria. The water is very high in arsenic as well. The water that flows over the mats contains hydrogen sulfide that is volcanic in origin and it flows very rapidly over these mats. There is absolutely no oxygen."
The team also showed that the mats were making carbonate deposits and creating a new generation of stromatolites. The carbonate materials also showed evidence for arsenic cycling-that arsenic is serving as a vehicle for electrons-proving that the microbes are actively metabolizing arsenic, much like oxygen in modern systems. Visscher says these findings, along with the fossil evidence, gives a strong sense of the early conditions of Earth.
One microbe's meat is another microbe's poison.
Journal Reference:
Pieter T. Visscher, Kimberley L. Gallagher, Anthony Bouton, et al. Modern arsenotrophic microbial mats provide an analogue for life in the anoxic Archean [open], Communications Earth & Environment (DOI: 10.1038/s43247-020-00025-2)
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