Studies on the U-turn Motion of Magnetotactic Bacteria

The u-turn motion of magnetotactic bacteria in switching, linear magnetic fields has been studied enabling the magnetic moment to be calculated. The magnetic dipole within a magnetotactic bacterium, rotates through 180 degrees when the polarity of the applied magnetic field is reversed. From the time and diameter of the u-turns the magnetic moment may be estimated. Figure 4 shows a sequence of video frames capturing the motion of a swimming bacterium during a 3 u-turn, 2 second track. A typical turn diameter is 60 microns, with a bacterium swimming at approximately 40 µm/s, under an applied field of 7 gauss (0.7 mT).