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How do microorganisms silicify? Experimental insights into microbial silicification mechanisms, rates, taphonomy, and physiological responses to entombment in silica - Stefan Lalonde

Stefan Lalonde - Laboratoire Domaines Océaniques, Université de Brest

Lundi 26 mai 2014 à 11 h

IMPMC - Site Buffon - 61, rue Buffon, Paris 5e

Salle des élèves - 2e étage




The oldest prokaryotic microfossils on Earth, spanning billions of years of geological history, are nearly all preserved in a siliceous (cherty) matrix. The process of microbial silicification can be observed today occurring at a variety of modern hot spring systems, where the chemical disequilibrium of venting hydrothermal fluids leads to the nucleation and growth of amorphous silica masses (sinter) and simultaneously the mineralization, and potential fossilisation, of many different types of microorganisms. Despite decades of research investigating this process in natural settings, several key questions remain that are best addressed through laboratory experiment: How strongly does silica interact with bacterial cell walls and other exposed surfaces (e.g. EPS)? Are there species-specific differences in the rate and mechanisms of silicification that may introduce bias in the fossil record? How do bacteria respond physiologically to growth under silica-mineralizing conditions? To what extent is microfossil morphology (e.g., length/width) preserved through early mineral diagenesis? This seminar will explore these and other questions through a survey of results from nearly a decade of diverse microbial silicification experiments in the laboratory.


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 Chiffres : janvier 2016