Magnetic response of Magnetospirillum gryphiswaldense observed inside a microfluidic channel

In this study we modelled and measured the U-turn trajectories of individual magnetotactic bacteria under the application of rotating magnetic fields, ranging in amplitude from 1 to 12 mT. The model is based on the balance between rotational drag and magnetic torque. For accurate verification of this model, bacteria were observed inside 5 μm tall microfluidic channels, so that they remained in focus during the entire trajectory. From the analysis of hundreds of trajectories and accurate measurements of bacteria and magnetosome chain dimensions, we confirmed that the model is correct within measurement error. The resulting average rate of rotation of Magnetospirillum gryphiswaldense is 0.74 ± 0.03 rad/mTs.