Dresden 2020 – scientific programme
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BP: Fachverband Biologische Physik
BP 16: Poster IV
BP 16.11: Poster
Tuesday, March 17, 2020, 14:00–16:00, P2/EG
Can the Motility of Magnetotactic Bacteria be Measured by Means of Magnetization Curves? — Sophia Nagelstrasser1, Frank Mickoleit2, Dirk Schüler2, Ingo Rehberg1, and •Reinhard Richter1 — 1Experimentalphysik 5, Universität Bayreuth, 95447 Bayreuth, Germany — 2Mikrobiologie, Universität Bayreuth, 95447 Bayreuth, Germany
The magnetization of a paramagnetic gas, like oxygen, increases with the applied magnetic field H and saturates if all magnetic moments m are aligned. This curve is described by M(H)=Φ L(ξ), where Φ denotes the volume fraction of the molecules, L(ξ) the Langevin function, and ξ = m H/(kB T) the ratio of magnetic and thermal energy. This function should also apply to a dispersion of magnetotactic bacteria, like the model organism Magnetospirillum gryphiswaldense. However, whereas the molecules have identical magnetic moments, those bacteria biomineralize a variing number of magnetite crystals (so called magnetosomes), with 20-60 particles per cell [1]. Moreover, in contrast to the molecules, which are passively kicked by kB T, the bacteria are actively swimming in their environment. In a series of measurements we are elucidating, whether the M(H)-curves of this active suspensions can still be described by a superposition of Langevin functions [2], capturing their motility by an enhanced effective temperature.
[1] R. Uebe and D. Schüler, Nat. Rev. Microbiol., 14 (2016) 621.
[2] I. Rehberg, R. Richter, S. Hartung, N. Lucht, B. Hankiewitz, T. Friedrich, Phys. Rev. B, 100 (2016) 134425.