Magnetotactic Bacteria

Magnetotactic bacteria (likely magnetococci) enriched from an environmental sample at Woods Hole are forced to swim to the edge of a water droplet with a bar magnet.  Removal of the magnet results in cells swimming away from the edge of the droplet.  Video courtesy of Dr. Meghan Byrne.

Magnetotactic Bacteria

Same as the video above except that the enriched bacteria are a population of Multicellular Magnetic Prokaryotes.  In this video you can see the bacteria return to the same location after the magnetic field is restored.  Video by Dr. Sheri Simmons.

Magnetic Response I

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.

Magnetic Response II

This is another way to visualize the turning of cells in a magnetic field.  The light scattering properties of a bacterial culture (specifically of bacteria that are asymmetric in shape) will differ based on the orientation of the cells relative to a light source.  When a magnet is placed parallel to a tube, bacteria are aligned such that light passes through their cellular short axis.  In this orientation a magnetic culture will scatter less light than when the cells are aligned perpendicular to the light. For nonmagnetic bacteria, there is no preferred orientation and thus the same level of light scattering is observed. In this video, the culture on the left is grown with iron and the one on the right is grown without iron.  Notice that the culture on the left becomes cloudier when the magnet is perpendicular to the tube.  By applying the same principle to a spectrophotometer we can quantitate the magnetic response of a culture, a measurement that is known as Cmag.  Video: Arash Komeili, Hand model: Dr. Dorothee Murat.

Cellular Organization of AMB-1

This incredible electron cryotomography video highlights many of the intricate features that characterize the subcellular organization of magnetosomes in AMB-1.  As the video moves through a cell magnetosomes and the filaments surrounding them are highlighted.  We then see the organization of the chain within the cell.  In AMB-1 magnetosomes are clearly invaginations of the inner cell membrane providing a mechanism for integrating the magnetic organelle into the cell structure.  Detailed results relating to this video can be found in Komeili, Li, Newman and Jensen, Science 2006).  Video by: Dr. Zhuo Li and Professor Grant Jensen.

Cellular Organization of RS-1

This video showcases the cellular strucutre of Desulfovibrio magneticus RS-1.  This organism is highly divergent from AMB-1 and forms tooth-shaped crystals of magnetite.  In our study of its biomineralization dynamics we found that it differed from AMB-1 in a number of interesting ways.  Most importantly, it contained a second iron-containing organelle unrelated to magnetosomes and its magnetite crystals did not appear to be surrounded by a biological membrane. In this video, the results of an electron cryotomography study of RS-1 ultrasturcture are highlighted.  For more information see: Byrne et al. PNAS 2010.  Video by: Dr. David Ball and Professor Kenneth Downing.