Figure 23.

Model of iron uptake and magnetite formation mechanism in magnetotactic bacteria. (A) Step 1: Ferritin and iron ions are transported through the cytoplasmatic membrane of the bacteria and a phosphate-rich Fe^III hydroxide phase is formed. (B) Step 2: Magnetite biomineralization starts by transport of iron ions and ferritin into the magnetosome vesicles where Fe²⁺ and Fe³⁺ ions coprecipitate to a ferrihydrite-like intermediate. (C) Step 3: Ferrihydrite is converted to magnetite, and (D) Step 4: it grows fully formed magnetosomes. (E) Ferritin protein complex. (F) HR-TEM image of the magnetosome from magnetotactic Gammaproteobacteria strain SS-5. Mechanism adapted from [151] with permission from John Wiley and Sons. Image (E) authored by Vossmann, and reproduced under the terms of the GNU General Public License. Image (F) by Pósfai, Lefèvre, Trubitsyn, Bazylinski and Frankel, 2013, reproduced under the terms of the Creative Commons Attribution License (CC BY).