Trapping single amphitrichous magnetotactic bacteria in small compartments for flow imaging

Magnetotactic Bacteria (MTB) are unicellular microoxic organisms that align with magnetic field lines. They orient and swim along the Earth's magnetic field in search of favourable environments; this process is called magnetotaxis. One can take advantage of MTB’s magnetic properties by generating an external magnetic field to direct their motion. There are exciting applications for MTB in many fields, for example nanorobotics and nanomedicine. However, to take full advantage of this magnetic control opportunity, we need to know more about the propulsion mechanism of MTB. We are interested in one species of MTB, Magnetospirillum magneticum AMB-1, which are corkscrew-shaped and amphitrichous (having a flagellum on either pole). A flow field map has not yet been experimentally determined for amphitrichous bacteria. We have tested different entrapping methods to be able to image a single, genetically engineered fluorescent AMB-1 cell in a micron-sized pit together with fluorescent beads. This way, we can image and track the bacteria and reconstruct the flow field they generate using the beads and particle tracking velocimetry. We thus hope to answer questions about the respective roles of the leading and trailing flagella, as well as that of the corkscrew body, in propulsion.