Thermal fluctuations of non-motile magnetotactic bacteria in AC magnetic fields

2008 ◽  
Vol 44 (3) ◽  
pp. 223-236 ◽  
Author(s):  
K. Ērglis ◽  
L. Alberte ◽  
A. Cēbers
Keyword(s):  
Magnetic Fields ◽  
Magnetotactic Bacteria ◽  
Thermal Fluctuations

scholarly journals Imposing Local Magnetic Fields to Control Magnetotactic Bacteria Through Combining Microfabrication and Magnetism

2011 ◽  
Vol 100 (3) ◽  
pp. 514a
Author(s):  
Lina M. Gonzalez ◽  
Warren C. Ruder ◽  
SiYen Chou ◽  
Eli Zenkov ◽  
William Messner ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Magnetotactic Bacteria ◽  
Local Magnetic Fields

Sensing of Local, Highly Concentrated Magnetic Field Gradients in Magnetotactic Bacteria Induces Motility Reversal

2012 ◽  
Author(s):  
Lina M. González ◽  
Warren C. Ruder ◽  
William C. Messner ◽  
Philip R. LeDuc
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetotactic Bacteria ◽  
Chemical Gradients ◽  
Field Gradients ◽  
Magnetic Field Gradients ◽  
Direction Of Movement ◽  
Unicellular Organisms ◽  
Sense And Respond ◽  
Direction Reversal

Many motile unicellular organisms have evolved specialized behaviors for detecting and responding to chemical gradients (chemotaxis) or oxygen (aerotaxis), while magnetotactic bacteria sense magnetic fields to align their direction of movement. Herein we show that Magnetospirillum magneticum (AMB-1) have the ability to sense and respond not only to the direction of magnetic fields of naturally occurring magnitude, but also to local, highly concentrated magnetic field gradients that do not occur in their natural environment. We imposed these gradients through our system integrating Helmholtz coils and permalloy (Ni80Fe20) microstructures. The AMB-1 exhibit three distinct behaviors as they approached gradients near the microstructures—unidirectional, single direction reversal, and double direction reversal. These results indicate previously unknown capabilities of the magnetic sensing systems of AMB-1.

High-Tc rf SQUIDs for operation in magnetic fields. Effect of thermal fluctuations

1999 ◽  
Vol 25 (10) ◽  
pp. 826-828 ◽  
Author(s):  
V. I. Shnyrkov ◽  
V. P. Timofeev ◽  
A. S. Garbuz ◽  
Cheol Gi Kim
Keyword(s):  
Magnetic Fields ◽  
Thermal Fluctuations ◽  
High Tc ◽  
Rf Squids

scholarly journals Critical superparamagnetic/single-domain grain sizes in interacting magnetite particles: implications for magnetosome crystals

2008 ◽  
Vol 6 (41) ◽  
pp. 1207-1212 ◽  
Author(s):  
Adrian R. Muxworthy ◽  
Wyn Williams
Keyword(s):  
Magnetotactic Bacteria ◽  
Thermal Fluctuations ◽  
Single Domain ◽  
Magnetic Interactions ◽  
Threshold Size ◽  
Grain Sizes ◽  
Magnetite Particles

Magnetotactic bacteria contain chains of magnetically interacting crystals (magnetosome crystals), which they use for navigation (magnetotaxis). To improve magnetotaxis efficiency, the magnetosome crystals (usually magnetite or greigite in composition) should be magnetically stable single-domain (SSD) particles. Smaller single-domain particles become magnetically unstable owing to thermal fluctuations and are termed superparamagnetic (SP). Previous calculations for the SSD/SP threshold size or blocking volume did not include the contribution of magnetic interactions. In this study, the blocking volume has been calculated as a function of grain elongation and separation for chains of identical magnetite grains. The inclusion of magnetic interactions was found to decrease the blocking volume, thereby increasing the range of SSD behaviour. Combining the results with previously published calculations for the SSD to multidomain threshold size in chains of magnetite reveals that interactions significantly increase the SSD range. We argue that chains of interacting magnetosome crystals found in magnetotactic bacteria have used this effect to improve magnetotaxis.

Extra sensory receptors

2019 ◽  
pp. 217-240
Author(s):  
Gordon L. Fain
Keyword(s):  
Molecular Biology ◽  
Magnetic Fields ◽  
Channel Gating ◽  
Magnetotactic Bacteria ◽  
Structure And Function ◽  
Sensory Transduction ◽  
Sensory Receptors ◽  
Sensory Modalities ◽  
Migrating Birds ◽  
And Function

“Extra sensory receptors” is the tenth chapter of the book Sensory Transduction and reviews mechanisms of sensory transduction in three additional sensory modalities: thermoreception, electroreception, and magnetoreception. It describes the physiology and molecular biology of warm and cold receptors in the mammalian skin, including the channels thought to be responsible and mechanisms of channel gating. There follows an extensive description of thermoreceptors in the pit organs of snakes which permit these animals literally to see in the dark. The section on electroreception reviews in detail the mechanism responsible for the astonishing sensitivity of the ampullary receptors of skates, as well as the structure and function of tuberous receptors, electrocytes, and electrolocation. The final section on magnetoreception describes magnetotactic bacteria as well as the evidence for magnetoreception in migrating birds, together with theories—as yet unproved—for the mechanism of animal sensitivity to magnetic fields.

scholarly journals Characterization of Bacterial Magnetotactic Behaviors by Using a Magnetospectrophotometry Assay

2009 ◽  
Vol 75 (12) ◽  
pp. 3835-3841 ◽  
Author(s):  
Christopher T. Lefèvre ◽  
Tao Song ◽  
Jean-Paul Yonnet ◽  
Long-Fei Wu
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Light Beam ◽  
Geomagnetic Field ◽  
Magnetic Particles ◽  
Magnetotactic Bacteria ◽  
Cell Alignment ◽  
The North ◽  
Field Lines ◽  
A Chain

ABSTRACT 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.

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