Dynamics of Magnetotactic Bacteria in a Rotating Magnetic Field

Abstract

The dynamics of the motile magnetotactic bacterium Magnetospirillum gryphiswaldense in a rotating magnetic field is investigated experimentally and analyzed by a theoretical model. These elongated bacteria are propelled by single flagella at each bacterial end and contain a magnetic filament formed by a linear assembly of approximately 40 ferromagnetic nanoparticles. The movements of the bacteria in suspension are analyzed by consideration of the orientation of their magnetic dipoles in the field, the hydrodynamic resistance of the bacteria, and the propulsive force of the flagella. Several novel features found in experiments include a velocity reversal during motion in the rotating field and an interesting diffusive wandering of the trajectory curvature centers. A new method to measure the magnetic moment of an individual bacterium is proposed based on the theory developed.

Polarity of bacterial magnetotaxis is controlled by aerotaxis through a common sensory pathway

“…As has been shown for other polarly flagellated bacteria 37,38 , M. gryphiswaldense does not tumble between smooth swimming phases, but instead swims in a typical run and reversal pattern, with speeds between 20 and 65 mm s À 1 , similar to previously reported values 12,13,39 . In equilibrium conditions, cells showed a reversal frequency of 0.126 s À 1 or less, which is low compared with data reported for non-MTB [40][41][42][43] .…”

“…M. gryphiswaldense has been widely used as a model in many recent studies on magnetosome biosynthesis 11 . However, there has been little investigation of its motility and taxis 8,12,13 , and it is currently not known whether or how the magnetic behaviour of M. gryphiswaldense and other MTB is integrated with other sensory responses at the behavioural and molecular level, or whether it uses a dedicated sensing and signalling machinery.…”

Ellipsoidal Brownian self-driven particles in a magnetic field

“…Despite the differences in the ferromagnetic and paramagnetic moments, the two-dimensional rotating magnetic field setup renders similar mathematical structures in the equation of motion in these different cases. Under a rotating magnetic field, a ferromagnetic microswimmer hence also displays synchronous and asynchronous behaviors similar to a paramagnetic microswimmer [29,30]. Finally, it may be biologically relevant to investigate the effects of the run and tumble motility of bacterial cells on the transition from anisotropic to isotropic diffusion.…”

“…Other related studies to the present work are: The theoretical and experimental study on the dynamics of a microswimmer with a L−shape made by Kummel et al [8], the dynamics of living active particles with a permanent magnetic moment (magnetotactic bacteria) in a rotating field treated by Cebers and coworkers [28,29], and the diffusive behavior of magnetotactic bacteria due to the random switching of the microorganisms flagellar motors reported in [30].…”

Sudden motility reversal indicates sensing of magnetic field gradients in Magnetospirillum magneticum AMB-1 strain

“…For example, Greenberg reported 'ping-pong' movements associated with magnetotactic multicellular organisms (Greenberg et al, 2005). Erglis et al (2007) also observed a 'back and forth' motion when studying the dynamics of Magnetospirillum gryphiswaldense in a rotating uniform magnetic field. An early study by Spormann and Wolfe (1984) called a observed reversal behavior 'tactile behavior,' and they demonstrated the maintenance of a band of cells while aligning the cells with a magnet.…”