Abstract
‘Candidatus Magnetoglobus multicellularis’ is the most studied multicellular magnetotactic prokaryote. It presents a light-dependent photokinesis: green light decreases the translation velocity whereas red light increases it, in comparison to blue and white light. The present article shows that radio-frequency electromagnetic fields cancel the light effect on photokinesis. The frequency to cancel the light effect corresponds to the Zeeman resonance frequency (DC magnetic field of 4 Oe and radio-frequency of 11.5 MHz), indicating the involvement of a radical pair mechanism. An analysis of the orientation angle relative to the magnetic field direction shows that radio-frequency electromagnetic fields disturb the swimming orientation when the microorganisms are illuminated with red light. The analysis also shows that at low magnetic fields (1.6 Oe) the swimming orientation angles are well scattered around the magnetic field direction, showing that magnetotaxis is not efficiently in the swimming orientation to the geomagnetic field. The results do not support cryptochrome as being the responsible chromophore for the radical pair mechanism and perhaps two different chromophores are necessary to explain the radio-frequency effects.
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Acknowledgments
We thank Dr. Henrique Lins de Barros for fruitful discussions, to both anonymous reviewers for their comments and suggestions, and to Dr. Donald Ellis of Northwestern University for reading and correcting the English grammar. RDM acknowledges financial support by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico–CNPq and DAA acknowledges financial support by Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro– FAPERJ and CNPq.
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de Melo, R.D., Acosta-Avalos, D. Light effects on the multicellular magnetotactic prokaryote ‘Candidatus Magnetoglobus multicellularis’ are cancelled by radiofrequency fields: the involvement of radical pair mechanisms. Antonie van Leeuwenhoek 110, 177–186 (2017). https://doi.org/10.1007/s10482-016-0788-0
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DOI: https://doi.org/10.1007/s10482-016-0788-0