8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Tue 611:23-14:00P10.29Swimming behaviour of magnetotactic bacteria M.GryphiswaldenseMathias Reufer, 1 Rut Besseling, 1 Jana Schwarz-Linek, 1 and Wilson Poon 21 University of Edinburgh, Institute for Condensed Matter and Complex Systems,Mayfield Road EH9 2NG, Edinburgh, United Kingdom2 University of Edinburgh, Edinburgh, United KingdomSince their discovery over 30 years ago, magnetotactic bacteria have enjoyed a large amount of researchinterest. These motile bacteria assemble linear arrays of ferromagnetic particles in theircytoplasm. The resulting magnetic dipole orients their body passively parallel to a magneticfield similar to a compass needle. Orientation along the earth’s magnetic field lines is thoughtto ease the navigation towards environments with better life conditions for the cells. Their preferredenvironment is the oxic-anoxic transition zone on the bottom of chemically stratified water.Under laboratory conditions, magnetotactic bacteria form microaerophilic bands around air bubbles.Magnetotaxis and aerotaxis work together in these bacteria and they are thus also referred asmagneto-aerotactic. We investigate the band formation around air bubbles of M. Gryphiswaldensewith superimposed external magnetic fields. Interestingly, the band formation is found to be littleaffected by an external applied field. However, the swimming direction of the individual bacteriain the band-like structures follows the magnetic field lines. We study the swimming behaviour bytracking and DDM (differential dynamic microscopy). The resulting swimming speed distributionshows two distinct peeks at about 20 µm and 40 µm. We speculate that the lower swimming speedis stemming from a fraction of unipolar cells possessing only one flagellum just after cell division.29