Changes in magnetotropic bacteria in a magnetic field

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Changes in Magnetotactic Bacteria in a Magnetic Field

Dynamics of Magnetotactic Bacteria in Rotating Magnetic Fields

Magnetotactic bacteria, such as Magnetospirillum gryphiswaldense, exhibit unique behaviors when subjected to rotating magnetic fields. These bacteria contain magnetic filaments composed of ferromagnetic nanoparticles, which align with the magnetic field. Experimental observations reveal that these bacteria can reverse their velocity and display diffusive wandering in their trajectory curvature centers when exposed to a rotating magnetic field. This behavior is influenced by the orientation of their magnetic dipoles, hydrodynamic resistance, and the propulsive force of their flagella.

Genetic Response to Magnetic Stimulation

The genetic response of magnetotactic bacteria, specifically Magnetospirillum magneticum strain AMB-1, to electromagnetic fields has been studied to understand how magnetosome-related genes are regulated. When exposed to a uniform magnetic field, gene expression in AMB-1 is initially down-regulated after one hour but up-regulated after three hours, before stabilizing after eight hours. This suggests that magnetic stimulation can alter gene signaling related to magnetosome production, cytoskeletal, and flagellar regulation, providing potential targets for creating magnetically-inducible synthetic gene networks.

Morphological Changes Under Magnetic Fields

The morphology of magnetotactic bacteria can change under different magnetic field conditions. For instance, Magnetospirillum magnetotacticum shows significant morphological changes, such as increased width and decreased length, when exposed to magnetic fields. In contrast, Magnetospirillum gryphiswaldense does not exhibit significant morphological changes under similar conditions. These differences suggest that the packaging of magnetosomes within the bacteria may vary between strains, which is crucial for applications like magnetically directed drug delivery.

Growth Patterns Affected by Magnetic Fields

Exposure to weak magnetic fields can influence the growth patterns of various bacterial species. Studies have shown that bacteria such as Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa exhibit altered growth rates when exposed to static, non-homogeneous, and alternating weak magnetic fields. Generally, these fields decelerate bacterial growth, even after the magnetic field is removed, indicating a lasting impact on bacterial proliferation.

Magnetic Properties During Bacterial Proliferation

Artificially magnetized bacteria, such as Lactobacillus fermentum labeled with maghemite nanoparticles, demonstrate that magnetic properties can dilute during bacterial proliferation. As bacteria divide, the magnetic nanoparticles are distributed among daughter cells, leading to a decrease in overall magnetic properties. This finding highlights the dynamic nature of magnetism in living systems and its potential applications in bionanotechnology.

Magnetosome Chain Orientation in Magnetic Fields

The orientation of magnetosome chains in Magnetospirillum magneticum AMB-1 can be influenced by external magnetic fields. When immobilized within a hydrated silica matrix, these bacteria show a deviation in magnetosome chain orientation without affecting cell viability. This reorientation is accompanied by a shift from parallel to anti-parallel interactions between nanocrystals, demonstrating the dynamic character of magnetosome assembly and its potential in bionanotechnology applications.

Effects of Low-Frequency Magnetic Fields on Bacterial Viability

Low-frequency magnetic fields can significantly impact the viability and growth of bacteria such as Escherichia coli. Exposure to these fields results in decreased bacterial growth and oxidoreductive activity, with the effects being more pronounced with higher field intensity and longer exposure times. This bactericidal effect is strain-dependent, with E. coli showing the highest sensitivity compared to other strains like Staphylococcus aureus .

Conclusion

Magnetotactic bacteria exhibit a range of responses to magnetic fields, including changes in dynamics, genetic expression, morphology, growth patterns, and magnetic properties. These responses are influenced by the type and strength of the magnetic field, as well as the specific bacterial strain. Understanding these changes is crucial for applications in bionanotechnology and targeted drug delivery, where the magnetic properties of bacteria can be harnessed for innovative solutions.