Frenkel Department of Physics, Cal Poly State University, San Luis Obispo, CA 93407
(rfrankel @ calpoly. Education)
sensitive to the magnetic field behavior of the bacteria was discovered more than 30 years ago
microbiologist Richard P. Blakemore. The discovery was based on the fact that certain
motile, aquatic bacteria orient and migrate along magnetic field lines
when subjected to a magnetic field of the order of the geomagnetic field, or
more. For sensitive to the magnetic field of bacteria (MTB) of the Northern Hemisphere collection
sites, the preferred direction of migration in the drops of water and sediment at the >> << a glass microscope slide parallel to the magnetic field corresponding to the north
migration of the geomagnetic field. The rate of migration of individual bacteria
along the lines of the magnetic field depends on the field, but can be 90% or more
forward speed of swimming cells (which can be up to 150 microns per second
). If the direction of the local magnetic field is reversed in the MTB
are swimming, they do turn and continue to migrate to >> << the same direction relative to the local magnetic field. The predominant direction of migration
MTB in a magnetic field may be canceled, provided >> << cells to a strong (up to several hundred gauss) magnetic field pulse oriented opposite
surrounding field. Mtb that spontaneously migrate south along the geomagnetic lines
fields are in water sediments and waters of the Southern Hemisphere.
[For a more complete description
magnetotaxis see Magnetotaxis bacteria (MTB All
contain magnetosomes, which are nanometer-sized magnetic, mineral crystals are enclosed in
; membrane. In most cases, magnetosomes arranged in a chain or chains seem
fixed within the cell adjacent to the membrane. In many strains of MTB,
magnetosome crystals of magnetite Fe, characterized
narrow distribution of size and shape, species specificity
crystal habit. crystal sizes typically range from ca. 40 to 100 nm
are in a constant, a single magnetic domain size range for magnetite. In MTB from marine sulphidic environments, magnetosome crystals
iron-sulfide mineral greigite, Fe, which is isostructural
magnetite and also ferrimagnetically ordered at room temperature >>. << greigite crystals are also characterized by a narrow size distribution and
Certain habits the crystal. However, while
magnetite crystals in the magnetosome chains are usually oriented so that [111]
crystallographic axis of each particle is in the chain direction
greigite particles in the magnetosome chain usually oriented so that [100]
crystallographic axis of each particle are oriented along the chain direction. Although the majority of MTB strains or magnetite or greigite magnetosomes is
organism that has both magnetite and greigite magnetosomes organized in chains. To
cells with either magnetite or greigite magnetosomes, the chain of magnetosomes
is a permanent magnetic dipole fixed in bacteria. >> << magnetic dipole moment is usually large enough, so that
. therefore, bacteria, oriented in the geomagnetic field at room temperature
So magnetotaxis is a passive process in which the orientation of the magnetic dipole >> << in the ambient magnetic field, as the body floats
causes it to migrate along magnetic field lines. killed cells to align along the field
rather than migration. So moving MTB itself as a self-propelled
magnetic compass needle. Mtb have two possible magnetic polarity , depending on the orientation of the magnetic dipole
inside the cell. polarity can be changed by a magnetic >> << pulse that is greater than the coercive force of the chain particles
(several hundred gauss). bacteria with reversed polarity migrate along magnetic field lines >> << in the opposite direction that the bacteria with the original polarity >>. << In their natural habitat, the predominant type of polarity in Population >> << this type of bacteria is determined by the sign of the slope
geomagnetic field. It was reported that high concentrations occur in the MTB
horizontal plates in an oxygen-anoxic transition zone (OATZ) in chemically << Marine >> stratified medium. Under these conditions, downward oxygen diffusion from the
surface diffusion and upward sulfide, resulting in
bacterial sulfate reduction in anaerobic sediments, creating a double vertical
chemical concentration gradient system, the oxidation- reduction concomitent gradient.
Salt Pond, 5 feet deep pond in the coastal Falmouth, Massachusetts on Cape Cod, the summer stratified >> << OATZ about 3 meters. MTB concentration >> < <a plate 10
cells per ml. At least seven
morphologically-distinct, sensitive to the magnetic field, bacterial type occur in OATZ, some containing particles
Fe3O4, and some of the buy strattera particles containing the Fe3S4 [21]. >> << magnetite-containing cells tend to be more abundant in the upper part of the plate in
relatively oxygen-rich part of OATZ, and greigite-containing cells
tend to be more abundant the bottom of the plate, in a relatively sulfide-rich >> << Part OATZ. Publications magnetotatic bacterial Richard B. Frankel (
(
Download the latest survey is sensitive to the magnetic field of the bacteria, (
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