MagMorphogens: Identification and functional analysis of shape-controlling determinants in bacterial magnetite biomineralization

• Applicant: Professor Dr. Dirk Schüler
• Subject Area: Metabolism, Biochemistry and Genetics of Microorganisms ; Biomaterials
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 564152354

Magnetosomes biomineralized by different magnetotactic bacteria display a variety of genetically encoded highly uniform morphologies such as elongated and bullet-shaped crystals, which clearly deviate from the isotropic octahedral equilibrium shape of abiotically synthesized magnetite nanoparticles. This suggests a higher degree of biological control on formation of anisotropic magnetosomes compared to the simpler morphology of isotropic cuboctahedric shapes produced by the well-studied magnetospirilla. It has been hypothesized that the biomineralization of morphologically distinct magnetite crystals is likely accounted for by variations among the numerous biosynthetic magnetosome genes by as yet unknown mechanisms. However, since most bacteria biomineralizing anisotropic magnetosomes are intractable, nothing is known about their crystal shape control at the molecular level. Therefore, a heterologous approach is suggested, in which biosynthetic magnetosome gene clusters from various intractable donors forming anisotropic magnetosomes will be expressed in the genetically amenable bacterium Magnetospirillum gryphiswaldense, naturally producing isotropic cuboctahedral magnetosomes, as surrogate host for genetic and biochemical analysis of ‘morphogens’. Magnetosome gene clusters from various magnetotactic alphaproteobacteria will be assembled and cloned by recently established technologies, and transferred into different mutant backgrounds of M. gryphiswaldense, which will be screened for the biomineralization of elongated anisotropic magnetite crystals. After delineation of candidate genes, identified proteins with morphogenic activity will be studied in depth with respect to their localization, function, and interaction within the proteo-lipid magnetosome membrane, in order to deduce the biological mechanism of elongated shape control. Finally, key morphogenic genetic building blocks will be combined in a synthetic biology approach for the production and analysis of morphology-modified magnetosome particles. An understanding of anisotropic shape control could be exploited for the engineering of ‘nanorods’ with enhanced and tuneable, so far largely unexplored magnetic characteristics potentially useful in various biomedical applications. Overall, the project will provide novel insights into the cell biology and biomineralization of a stunningly diverse group of microorganisms and set the stage for future exploration of distinct magnetosome pathways in intractable and uncultured bacteria.

• DFG Programme: Research Grants