One of the most intriguing examples for biogenic nanoparticles are found in magnetotactic bacteria (MTB). MTB synthesize intracellular, enveloped crystals of magnetite (Fe3O4) called magnetosomes. These characteristics are features of a process called biologically controlled mineralization (BCM), in which the organism exerts a crystallochemical control over the mineral precipitation. Because of these features, BCM of magnetosomes is a unique process that has been the focus of strong interdisciplinary interest.
Indeed, magnetite crystals have been used as presumptive signature for life on Mars and magnetic nanoparticles with advanced characteristics have many biomedical and nanobiotechnological applications. Mostly because of the previous unavailability of an appropriate laboratory model little is known about how these bacteria bio-mineralise their magnetic inclusions at the biochemical and molecular level. Consequently, the mechanism of the physico-chemical control remains largely unknown and needs to be specified.
The objective of our research is therefore to elucidate a BCM process and particularly magnetosome formation in Magnetospirillum gryphiswaldense the molecular and the physico-chemical level. We aim understanding the physico-chemical conditions governing magnetite formation within the magnetosomes, and the role of biological molecules involved in interactions at the organic-inorganic interface. Such an objective will imply in vivo microbiological experiments with bacteria, and in vitro inorganic experiments including biomolecules to mimic in situ conditions.
These biomolecules are expected to affect reaction kinetics, and geochemical properties of the crystals when compared to purely inorganic synthesis. This requires an integrated approach involving strong interactions between microbiologists headed by Dr. D. Schuler (the researcher) and aqueous geochemist (D. Faivre, the research fellow) to tackle the problem of the complete iron reaction sequence.
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