A New Study of Bacterial Motion: Superconducting Quantum Interference Device Microscopy of Magnetotactic Bacteria

The recently developed “microscope” based on a high-T c dc SQUID (superconducting quantum interference device) is used to detect the magnetic fields produced by the motion of magnetotactic bacteria, which have permanent dipole moments. The bacteria, in growth medium at room temperature, can be broug...

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Bibliographic Details
Published in:Biophysical journal 1999-06, Vol.76 (6), p.3323-3330
Main Authors: Chemla, Y.R., Grossman, H.L., Lee, T.S., Clarke, John, Adamkiewicz, M., Buchanan, B.B.
Format: Article
Language:English
Subjects:
Bacteria
Biophysical Phenomena
Biophysics
Magnetics
Magnetism
Microbiology
Microscopy - methods
Movement
Quantum theory
Rhodospirillaceae - physiology
Space life sciences
Superconductivity
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Summary:The recently developed “microscope” based on a high-T c dc SQUID (superconducting quantum interference device) is used to detect the magnetic fields produced by the motion of magnetotactic bacteria, which have permanent dipole moments. The bacteria, in growth medium at room temperature, can be brought to within 15 μm of a SQUID at liquid nitrogen temperature. Measurements are performed on both motile and nonmotile bacteria. In the nonmotile case, we obtain the power spectrum of the magnetic field noise produced by the rotational Brownian motion of the ensemble of bacteria. Furthermore, we measure the time-dependent field produced by the ensemble in response to an applied uniform magnetic field. In the motile case, we obtain the magnetic field power spectra produced by the swimming bacteria. Combined, these measurements determine the average rotational drag coefficient, magnetic moment, and the frequency and amplitude of the vibrational and rotational modes of the bacteria in a unified set of measurements. In addition, the microscope can easily resolve the motion of a single bacterium. This technique can be extended to any cell to which a magnetic tag can be attached.
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(99)77485-0