Greigite or magnetite: Environmental and genetic determinants controlling biomineralization in magnetotactic bacteria

• Applicant: Dr. Damien Faivre
• Subject Area: Microbial Ecology and Applied Microbiology ; Biological and Biomimetic Chemistry ; Biomaterials ; Metabolism, Biochemistry and Genetics of Microorganisms ; Structural Biology
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 258774416

There is a variety of materials formed by organisms, which often have superior properties than similar man-made materials, even if they are made with a limited amount of elements and under physiological conditions. Magnetosome chains in magnetotactic bacteria represent a biological paradigm of such a biological material, where magnetic nanocrystals with controlled properties are synthesized in organelles called magnetosomes and arranged into linear chains. These chains serve the cells to align along the Earth's magnetic field lines. The magnetosomes are made of a magnetite [Fe(II)Fe(III)2O4] or greigite [Fe(II)Fe(III)2S4] crystal embedded in a lipidic vesicle. Until recently, only magnetite-building strains were available in pure culture. Thus, the molecular and physico-chemical knowledge of the biomineralization mechanism steadily advanced in the recent years for those strains, but dramatically lags behind for greigite-mineralizing bacteria. With the isolation of a new type of cells, BW-1, we now have a model organism in our hands, which is able to form both magnetite and greigite. In this project, we thus propose an integrated and multidisciplinary approach to understand greigite biomineralization in magnetotactic bacteria. We will in particular study the environmental condition favoring the production of magnetite or greigite as well as the chemical reaction pathway leading to the formation of each magnetite and greigite in this BW-1 strain. In addition, we will determine what are the biological determinants involved in the biomineralization process with a particular focus on redox proteins such as the recently discovered magnetochrome. Finally, we will use this biological determinant in in vitro mineralization experiments to test their effect in biomimetic experiments. Our results will be of immediate relevance for the fundamental understanding of biomineralization in vivo. In addition, we anticipate our outcomes to be the starting point towards a more quantitative description of the role biological additives can have on the control of magnetic nanoparticles in the beaker.

• DFG Programme: Research Grants
• International Connection: France
• Participating Persons: Professor Nicolas Menguy; Dr. David Pignol