Regulation of iron metabolism and magnetite formation in Magnetospirillum gryphiswaldense

• Applicants: Professor Dr. Berthold F. Matzanke-Markstein; Professor Dr. Dirk Schüler
• Subject Area: Metabolism, Biochemistry and Genetics of Microorganisms
• Term: from 2011 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 192622306

Magnetotactic bacteria synthesize specific organelles, the magnetosomes, which are membrane-enveloped crystals of the magnetic mineral magnetite (Fe3O4). The biomineralization of magnetite involves the uptake and intracellular accumulation of large amounts of iron. However, it is not clear how iron uptake and biomineralization is regulated and balanced with the biochemical iron requirement and intracellular homeostasis. In this proposal, we plan to identify major routes for uptake and intracellular storage of iron, and we shall analyse their regulation and interconnection with magnetite biomineralization by an interdisciplinary and collaborative approach. Mutants which are deleted in genes for various putative iron uptake systems as well as for proteins from the Fur-like family impli-cated in global iron regulation will be analyzed with respect to growth, iron accumulation, and magne-tite biomineralization. Iron metabolites will be identified by quantitative in situ Mössbauer fingerprint techniques. In addition, isolation of magnetosomes, membranes and cytoplasmic fractions will provide samples for detailed structural analysis by Mössbauer spectroscopy, nuclear forward scattering(NFS), XAS spectroscopy, and nuclear inelastic scattering (NIS) in whole and fractionated cells. In particular, we want to employ the new P01-beam line at DESY (Hamburg) allowing NRS with very small sample volumes (1μl) and local resolution to approx. 50nm. Biochemical and genetic analysis will then be used to identify and functionally characterize an elusive membrane-bound iron storage compound that has been implicated in magnetite biomineralization by previous Mössbauer experiments. Our studies will for the first time reveal a detailed and comprehensive picture of iron metabolism in magnetotactic bacteria and its integration with magnetosome biosynthesis at the molecular and mechanistic level. The results are expected to not only improve our understanding of pathways for magnetite biomineralization, but will also facilitate the biogenic synthesis and application of magnetic nanoparticles.

• DFG Programme: Research Grants