Wednesday, 30 September 2020

Arsenic and old lakes

Microbial Mats (purple) at Laguna La Brava Chile
From Visscher et al. 2020 CC BY 4.0

Atmospheric oxygen was not plentiful until the Great Oxidation Event yet life appeared much earlier during the Archean Eon (more than 3 gigayears ago). One suggestion has been that  arsenic acted as an electron donor to drive photosynthesis in early life forms.

A new paper by Visscher et al. shows how this might have worked. They investigated microbial mats from Laguna La Brava in northern Chile. These survive under hypersalinic and anoxic conditions by using arsenic and sulphur as electron donors.

A parallel is drawn with the Archean lakes of the Tumbiana Formation where lithified microbial mats are found. 

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