Collapse of the Magnetosome:
When the magnetotactic crystals are in an unstable arrangement the whole magnetosome will collapse without additional support. The collapse can occur during diagenesis and dolomitization. The magnetosome shape and elastic properties of biological membranes are what is holding the chains together, as well as the linearity and the connection to the cytoskeleton. With how much the geometries effect the stabilization of the chains of magnetosomes shows that they are intrinsically unstable.
The cell wall and associated membrane structures have been thought to act to prevent magnetosome chain collapse. There has been data collected that indicates that magnetosome linearity persists long after cells are disrupted. Consistent with prior observations, in some magnetococcus, the magnetosome chains pass through the cell interior, precluding continuous contact with the cell wall and imply additional support structures exist in some species. [1]
Purpose of the Magnetosome:
Magnetotactic bacteria are widespread, motile, diverse prokaryotes that biominieralize a unique organelle called the magnetosome. A magnetosome consists of a nano-sized crystal of a magnetic iron mineral, which is enveloped by a lipid bilayer membrane. In the cells of most all magnetotactic bacteria, magnetosomes are organized as well-ordered chains. The magnetosome chain causes the cell to behave as a motile, miniature compass needle where the cell aligns and swims parallel to magnetic field lines. [2]
The magnetic dipole moment of the cell is often large enough that its interaction with Earth’s magnetic field overcomes the thermal forces that tend to randomize the orientation of the cell in its aqueous surroundings. Magnetotactic bacteria use aerotaxis as well. Aerotaxis is a response to changes in oxygen concentration that will favor swimming towards a zone of optimal oxygen concentration. Lakes or oceans oxygen concentration is commonly dependent on depth. If the Earth’s magnetic field has a significant downward slant, the orientation along field lines aids in the search for the optimal concentration. This process being called magneto-aerotaxis.
- ^ Kobayashi, A.; Kirschvink, JL.; Nash, CZ.; Kopp, RE.; Sauer, DA.; Bertain, LE.; Voorhout, WF.; Taguchi, T. (2006). "Experimental observation of magnetosome chain collapse in magnetotactic bacteria: Sedimentological, paleomagnetic, and evolutionary implications". Earth and Planetary Science Letters. 245 (3-4): 538–550.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Keim, CN.; Martins, JL.; Abreu, F.; Rosado, AS.; de Barros, HL.; Borojevic, R.; Lins, U.; Farina, M. (2004). "Multicellular life cycle of magnetotactic prokaryotes". FEMS Microbiology Letters. 240 (2): 203–208.
{{cite journal}}: CS1 maint: multiple names: authors list (link)