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Applied and Environmental Microbiology, June 2009, p. 3835-3841, Vol. 75, No. 12
0099-2240/09/$08.00+0     doi:10.1128/AEM.00165-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Characterization of Bacterial Magnetotactic Behaviors by Using a Magnetospectrophotometry Assay{triangledown}

Christopher T. Lefèvre,1,{dagger} Tao Song,2 Jean-Paul Yonnet,3 and Long-Fei Wu1*

Laboratoire de Chimie Bactérienne, UPR9043, Université de la Méditerranée, Institut de Microbiologie de la Méditerranée, CNRS, F-13402 Marseille Cedex 20, France,1 Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100080, People's Republic of China,2 Laboratoire de Génie Electrique de Grenoble, UMR 5269, Grenoble-INP, F-38402 Saint Martin d'Hères Cedex, France3

Received 23 January 2009/ Accepted 6 April 2009

Magnetotactic bacteria have the unique capacity of synthesizing intracellular single-domain magnetic particles called magnetosomes. The magnetosomes are usually organized in a chain that allows the bacteria to align and swim along geomagnetic field lines, a behavior called magnetotaxis. Two mechanisms of magnetotaxis have been described. Axial magnetotactic cells swim in both directions along magnetic field lines. In contrast, polar magnetotactic cells swim either parallel to the geomagnetic field lines toward the North Pole (north seeking) or antiparallel toward the South Pole (south seeking). In this study, we used a magnetospectrophotometry (MSP) assay to characterize both the axial magnetotaxis of "Magnetospirillum magneticum" strain AMB-1 and the polar magnetotaxis of magneto-ovoid strain MO-1. Two pairs of Helmholtz coils were mounted onto the cuvette holder of a common laboratory spectrophotometer to generate two mutually perpendicular homogeneous magnetic fields parallel or perpendicular to the light beam. The application of magnetic fields allowed measurements of the change in light scattering resulting from cell alignment in a magnetic field or in absorbance due to bacteria swimming across the light beam. Our results showed that MSP is a powerful tool for the determination of bacterial magnetism and the analysis of alignment and swimming of magnetotactic bacteria in magnetic fields. Moreover, this assay allowed us to characterize south-seeking derivatives and non-magnetosome-bearing strains obtained from north-seeking MO-1 cultures. Our results suggest that oxygen is a determinant factor that controls magnetotactic behavior.

* Corresponding author. Mailing address: LCB UPR9043, CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France. Phone: 33-4 91164157. Fax: 33-4 91718914. E-mail: wu{at}ifr88.cnrs-mrs.fr

{triangledown} Published ahead of print on 17 April 2009.

{dagger} Present address: School of Life Sciences, University of Nevada at Las Vegas, Las Vegas, NV 89154.

Applied and Environmental Microbiology, June 2009, p. 3835-3841, Vol. 75, No. 12
0099-2240/09/$08.00+0     doi:10.1128/AEM.00165-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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