EVALUATION OF MAGNETOSENSITIVITY OF PHOTOBACTERIUM PHOSPHOREUM
Authors:   Taras Shevchenko National University of Kyiv, Kyiv, Ukraine, MARTYNIUK Viktor , TSEYSLYER Yuliya ,   Taras Shevchenko National University of Kyiv, Kyiv, Ukraine, GROMOZOVA Olena ,   D.K. Zabolotny Institute of Microbiology and Virology of NAS of Ukraine, Kyiv, Uktaine, HRETSKYI Igor ,   D.K. Zabolotny Institute of Microbiology and Virology of NAS of Ukraine, Kyiv, Uktaine
Published: February 2025

Introduction. Currently, research is being conducted to identify the mechanisms that enable living organisms to sense and utilize the Earth's magnetic field for orientation and navigation. The primary hypothetical mechanisms under active discussion include the radical pair model, which involves magnetosensitive free radical redox reactions in enzymatic systems containing oxygen molecules and flavin compounds (such as cryptochromes and bacterial luciferases), as well as the model involving intracellular magnetic magnetite particles interacting with the magnetic field. Our focus is on the first hypothesis. Therefore, the aim of our study was to investigate the effects of constant and extremely low frequency magnetic fields on the bioluminescence of Photobacterium phosphoreum, based on a flavin oxidation reaction. Notably, photobacteria are widely used as bioindicators of water pollution and indicators of exposure to various biologically active compounds.

Methods. We measured the bioluminescence of P. phosphoreum in liquid media of standard composition for bacterial nutrient medium at room temperature (22-24°C). The baseline bioluminescence was evaluated over several days following inoculation in the culture medium. Bioluminescence was recorded using digital photoregistration, with subsequent image processing conducted in ImageJ or OriginPro. Magnetic field exposure was applied in two modes. In the first mode, bacterial suspensions were exposed to the magnetic field continuously from the moment of inoculation throughout the entire growth period. In the second mode, short-term magnetic field exposure was applied for several minutes after active hydrodynamic stirring of the bacterial suspension, which triggered a burst of luminescence, followed by fading and return to the baseline level. The magnetic field induction was measured using a Hall sensor.

Results. Relatively strong static magnetic fields in the range of 2-8 mT weakly activated bioluminescence during the active growth phase of the bacterial population, but they statistically significantly suppressed the glow of bacteria during their maximum luminescence and subsequent dimming. The magnitude of the effects of the magnetic field was small, approximately 15% relative to the control values. The influence of a low-frequency magnetic field with a frequency of 7.85 Hz and induction of 100 μT stimulated the baseline bioluminescence of the photobacteria. At the same time, the magnetic field did not significantly affect either the concentration of oxygen or the concentration of bacterial cells in suspension, indicating a direct influence of magnetic fields on the metabolic processes associated with the bioluminescent system of bacterial cells. During short-term exposure to this extremely low frequency magnetic field, we observed a burst of luminescence initiated by the active hydrodynamic stirring of the bacterial suspension. This resulted in slow but statistically significant increase in the intensity of baseline bioluminescence by 5-10%.

Conclusion. P. phosphoreum is sensitive to the action of static and extremely low-frequency fields, showing a biological efficiency within 15% of the control values. This bacterial model of magnetosensitivity is convenient for further experimental verification of the hypothesis regarding the magnetosensitivity of radical pairs.

The work was supported by IEEE “Magnetism in Ukraine 2022/2023 initiative”, project “Development of a microbial test to evaluate the effect of geomagnetic field on biological systems”. Grant Agreement #99184