Abstract
Magnetotactic bacteria swim and orient in the direction of a magnetic field thanks to the magnetosome chain, a cellular ‘compass needle’ that consists of a string of vesicle-enclosed magnetic nanoparticles aligned on a cytoskeletal filament. Here we investigate the mechanical properties of such a chain, in particular the bending stiffness. We determine the contribution of magnetic interactions to the bending stiffness and the persistence length of the chain. This contribution is comparable to, but typically smaller than the contribution of the semiflexible filament. For a chain of magnetic nanoparticles without a semiflexible filament, the linear configuration is typically metastable and the lowest energy structures are closed chains (flux closure rings) without a net magnetic moment that are thus not functional as a cellular compass. Our calculations show that the presence of the cytoskeletal filament stabilizes the chain against ring closure, either thermodynamically or kinetically, depending on the stiffness of the filament, confirming that such stabilization is one of the roles of this structure in these bacterial cells.
Highlights
The interior of living cells is highly structured, with membrane-bounded compartments providing functionally specialized chemical conditions and a cytoskeleton providing both mechanical stability and spatial organization [1]
We have addressed the bending stiffness of magnetosome chains, which results from two main contributions, a magnetic one due to the magnetic interactions between magnetosomes that favor straight chain orientation, and an elastic contribution due to the bending stiffness of the actin-like cytoskeletal filament to which the magnetosomes are attached
Our analysis shows that while both contributions are relevant, the bending stiffness of the filament can usually be expected to be the dominant part, with an about four-fold longer persistence length than due to magnetic interactions alone
Summary
The interior of living cells is highly structured, with membrane-bounded compartments providing functionally specialized chemical conditions and a cytoskeleton providing both mechanical stability and spatial organization [1]. We ask whether the bending stiffness is mostly due to the cytoskeletal structure or to the magnetic interactions, as magnetic particles are known to form linear structures [17, 21] without a stabilizing filament and (short) chains have been seen in cells lacking the MamK protein [22, 23]. For such systems, it is known that magnetic particles form closed ring structures, so called fluxclosure rings [26,27,28], we consider whether an actin-like semiflexible filament can stabilize a linear chain of magnetosomes against ring formation either thermodynamically or kinetically
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
