title: Quantifying the magnetic advantage in magnetotaxis.
abstract: Magnetotactic bacteria are characterized by the production of magnetosomes, nanoscale particles of lipid bilayer encapsulated magnetite, that act to orient the bacteria in magnetic fields. These magnetosomes allow magneto-aerotaxis, which is the motion of the bacteria along a magnetic field and toward preferred concentrations of oxygen. Magneto-aerotaxis has been shown to direct the motion of these bacteria downward toward sediments and microaerobic environments favorable for growth. Herein, we compare the magneto-aerotaxis of wild-type, magnetic Magnetospirillum magneticum AMB-1 with a nonmagnetic mutant we have engineered. Using an applied magnetic field and an advancing oxygen gradient, we have quantified the magnetic advantage in magneto-aerotaxis as a more rapid migration to preferred oxygen levels. Magnetic, wild-type cells swimming in an applied magnetic field more quickly migrate away from the advancing oxygen than either wild-type cells in a zero field or the nonmagnetic cells in any field. We find that the responses of the magnetic and mutant strains are well described by a relatively simple analytical model, an analysis of which indicates that the key benefit of magnetotaxis is an enhancement of a bacterium's ability to detect oxygen, not an increase in its average speed moving away from high oxygen concentrations.
authors.affiliation: Chemistry Division, Naval Research Laboratory, Washington, District of Columbia 20375, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Smith
authors.forename: P E
authors.initials: PE
authors.lastname: Sheehan
authors.forename: L L
authors.initials: LL
authors.lastname: Perry
authors.forename: K
authors.initials: K
authors.lastname: O'Connor
authors.forename: L N
authors.initials: LN
authors.lastname: Csonka
authors.forename: B M
authors.initials: BM
authors.lastname: Applegate
authors.forename: L J
authors.initials: LJ
authors.lastname: Whitman
mesh_terms: D001703:Biophysics / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D004574:Electromagnetic Fields; D005297:Ferrozine / Q000737:chemistry / Q000493:pharmacokinetics* / Q000494:pharmacology; D005821:Genetic Techniques; D007501:Iron / Q000378:metabolism / Q000493:pharmacokinetics* / Q000494:pharmacology; D008051:Lipid Bilayers / Q000737:chemistry*; D008280:Magnetics; D042201:Magnetospirillum / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D008954:Models, Biological; D015233:Models, Statistical; D010100:Oxygen / Q000378:metabolism
chemical_list: D008051:Lipid Bilayers; D005297:Ferrozine; D007501:Iron; D010100:Oxygen