Accueil > Publications > Recherche par années > Années 2000 > 2006

Westall, F ; de Ronde, CEJ ; Southam, G ; Grassineau, N ; Colas, M ; Cockell, C ; Lammer, H

Implications of a 3.472-3.333 Gyr-old subaerial microbial mat from the Barberton greenstone belt, South Africa for the UV environmental conditions on the early Earth

Philosophical Transactions of The Royal Society B-Biological Sciences 361 (1474) 1857-1875

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Abstract :

Modelling suggests that the UV radiation environment of the early Earth, with DNA weighted irradiances of about three orders of magnitude greater than those at present, was hostile to life forms at the surface, unless they lived in specific protected habitats. However, we present empirical evidence that challenges this commonly held view. We describe a well-developed microbial mat that formed on the surface of volcanic littoral sediments in an evaporitic environment in a 3.5-3.3 Ga-old formation from the Barberton greenstone belt. Using a multiscale, multidisciplinary approach designed to strongly test the biogenicity of potential microbial structures, we show that the mat was constructed under flowing water by 0.25 mu m filaments that produced copious quantities of extracellular polymeric substances, representing probably anoxygenic photosynthesizers.