This is one way to visualize the magnetic response of a culture of magnetotactic bacteria. In this experiment, Magnetospirillum magneticum AMB-1 cells, grown in an iron-rich medium, have settled into a pellet at the bottom of a tube. The pellet can then be rapidly pulled towards a magnet placed on the side of the tube. Note that killing the cells will not change this response at all since it is mediated by attraction between the two sets of magnets. Video: Arash Komeili, Hand model: Dr. Dorothee Murat.