Fundamental Research Division
The DRF at the CEA assemble approximately 6,000 scientists since January 2016.
Scientific result | Bioremediation | MRI
An international consortium led by CEA researchers
in collaboration with the CNRS, has succeeded in characterizing the
structure and function of a protein involved in the production of
magnetite nanomagnets in magnetotactic bacteria. This protein, MamP, is
crucial to the metallurgical activity of the bacterium. It is this
protein that gives the magnetite its magnetic properties. This work
constitutes an important advance in the understanding of these bacteria
and the magnetite biomineralization process. It is expected to result in
the development of additional biotechnological applications for these
nanomagnets, especially in the fields of medical imaging and the
decontamination of water.
Magnetotactic bacteria have the ability to synthesize nanocrystals of
magnetite (Fe3O4) enabling them to align themselves with
the terrestrial magnetic field in order to find the position in the water column
that is most favorable to their survival. The alignment of the nanomagnets is
similar to that of a compass needle. The magnetite crystal synthesis process is
a complex one, and it is little understood at the present time. Magnetite is a
compound of oxygen and iron in a mixture of two different oxidation states
[Fe(II)Fe(III)2O4]. In this study, the researchers have
described the mechanism by which the bacterium produces these two states, one of
which, Fe(III), is essentially insoluble.
The determination of the structure of the protein MamP has shown for the
first time that a section of this protein possesses an original folding
structure known as a magnetochrome. This structure is only found in
magnetotactic bacteria. The structure has a crucible-like shape capable of
containing iron. Additional experiments have shown that MamP has the ability to
oxidize iron from the Fe(II) state to the Fe(III) state, and to stabilize the
latter in its crucible. Mutagenesis studies and the phenotyping of magnetotactic
bacteria variants have confirmed the physiological importance of this crucible.
Finally, a number of in vitro experiments have shown that MamP is
capable of producing a magnetite precursor when incubated in the presence of
Fe(II) alone, proving that the Fe (III) results from the activity of this
This fundamental study reveals part of the process whereby iron is
biomineralized and nanomagnets are synthesized in magnetotactic bacteria. The
potential applications of these nanomagnets appear promising. They may, for
example, by used as a contrast agent in magnetic resonance imaging. Another
possible application relates to the decontamination of water supplies.
Magnetotactic bacteria carrying an enzyme that breaks down a contaminant may be
used to treat effluent and may then easily be removed from the water by means of
Structural insight into magnetochrome-mediated magnetite biomineralization.
CEA is a French government-funded technological research organisation in four main areas: low-carbon energies, defense and security, information technologies and health technologies. A prominent player in the European Research Area, it is involved in setting up collaborative projects with many partners around the world.