Determination of the magnetic moment and geometrical dimensions of the magnetotactic bacteria using an optical scattering method

Abstract

We adapted an experimental technique for characterizing the magnetotactic bacteria and simplified it by transferring the burden to literal and numerical computation, which is an advantageous tradeoff. In a magnetic field the bacteria tend to orient their magnetic axes along the direction of the magnetic field, resulting in an anisotropic distribution of the orientation and, consequently, a significant change of the directional distribution of the scattering efficiency of light. We made a simple experimental arrangement for measuring the scattering efficiency of light by the bacteria in certain directions for various values of an external magnetic field applied to the bacteria. We inferred from the fitting of the experimental to the theoretical data the most probable values for the magnetic moment and the dimensions of the magnetotactic bacteria. In the experiments a wild-type Magnetospirillum gryphiswaldense strain was used.

Biology and Physics of Magnetotactic Bacteria

“…For two different cultures of Aquaspirillum magnetotacticum were determined values of (2.2 AE 0.2) Â 10 À13 emu and (4.3 AE 0.5) Â 10 À13 emu, which are in good agreement with the value obtained by electron microscopy, or about 4.4 Â 10 À13 emu. Using a similar experimental approach in [65] was determined the magnetic moment of a wild-type Magnetospirillum gryphiswaldense strain and obtained a value of about 25.3 (AE1.6) Â 10 À13 emu. Other methods found in literature are based basically in the analysis of the bacterial body rotation caused by the magnetic torque and in the analysis of the equation magnetic torque = viscous torque.…”