Control Characteristics of Magnetotactic Bacteria : Magnetospi r i l lumMagnetotact i cum Strain MS - 1 and Magnetospi r i l lumMagnet i cum Strain AMB - 1 Islam

Magnetotactic bacteria have the potential to execute nontrivial tasks, such as microactuation, micromanipulation, and microassembly, under the influence of the controlled magnetic fields. Closed-loop control characteristics of these magnetic microorganisms depend on their self-propulsion forces (motility) and magnetic dipole moments. These properties can be controlled through the growth conditions of magnetotactic bacteria. We provide a comparison between two species of magnetotactic bacteria, i.e., Magnetospirillum magnetotacticum strain MS-1 and Magnetospirillum magneticum strain AMB-1. This comparison includes the characterization of their morphologies, magnetic dipole moments, and closed-loop control characteristics in the transient and steady states. The characterized average magnetic dipole moments of motile cells of M. magnetotacticum and M. magneticum strains are 1.4 × 10−16 A.m2 and 1.5 × 10−17 A.m2 at a magnetic field of 7.9 mT, respectively. These magnetic dipole moments are used in the realization of closed-loop control systems for each bacterial strain. The closed-loop control systems achieve point-to-point positioning of M. magnetotacticum cells at an average velocity of 32 ± 10 μm/s (approximately seven body lengths per second), and within an average region of convergence of 23 ± 10 μm (approximately four body lengths), while cells of M. magneticum strain are positioned at an average velocity of 30 ± 12 μm/s (approximately eight body lengths per second), and within an average region of convergence of 35 ± 14 μm (approximately 14 body lengths). These results suggest that the cells of M. magnetotacticum strain have a slightly greater tendency to provide desirable closed-loop control characteristics than cells of M. magneticum strain.