Abstract
Magnetotactic bacteria (MTB) synthesize magnetosomes composed of membrane-enveloped magnetite (Fe3O4) or greigite (Fe3S4) particles in the cells. Recently, several studies have shown some possibilities of controlling the biomineralization process and altering the magnetic properties of magnetosomes by adding some transition metals to the culture media under various environmental conditions. Here, we successfully grow Magnetospirillum magneticum strain RSS-1, which are isolated from a freshwater environment, and find that synthesis of magnetosomes are encouraged in RSS-1 in the presence of samarium and that each core magnetic crystal composed of magnetite is covered with a thin layer of samarium oxide (Sm2O3). The present results show some possibilities of magnetic recovery of transition metals and synthesis of some novel structures composed of magnetic particles and transition metals utilizing MTB.
Highlights
Magnetotactic bacteria (MTB) form intracellular chains of magnetosomes, which contain membrane-enveloped magnetic crystals comprised of magnetite (Fe3O4) or greigite (Fe3S4) [1,2]
The surface of each magnetic particle synthesized by strain RSS-1 in the presence of 250 μM Fe quinate (Fe-q) and 250 μM Sm quinate (Sm-q) was covered with a thin layer (Fig 1B and 1C), which will be analyzed and discussed in more detail later
We confirmed that the surface of each magnetic particles synthesized by strain RSS-1 in the presence of only 250 μM Fe-q was not covered with any other layer including lipid membranes (S1 Fig)
Summary
Magnetotactic bacteria (MTB) form intracellular chains of magnetosomes, which contain membrane-enveloped magnetic crystals comprised of magnetite (Fe3O4) or greigite (Fe3S4) [1,2]. The size of magnetosomes ranges from 35 to 120 nm, and the shape varies depending on the bacterial strains. The size and shape are, highly uniform in each strain [3,4,5]. The biomineralization process is strictly controlled by the magnetosome-related genes. Such a high degree of control of the synthetic process of magnetosomes occurring in MTB has a significant advantage over the other synthetic methods of magnetic nanoparticles in terms of the morphological definition and biocompatibility [6,7,8,9]. Magnetosomes are of great importance considering their application to nanotechnology-based biomedical studies; e.g., they can be used as nano magnetic resonance imaging enhancing agents, nano hyperthermic cancer treatment media and nano drug delivery vehicles [10], the performances of which are totally dependent on the magnetic properties of the magnetosomes
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