Richard B.
Frenkel Department of Physics, Cal Poly State University, San Luis Obispo, California 93407
(rfrankel @ calpoly. Education)
sensitive to the magnetic behavior of bacteria was found more than 30 years ago
microbiologist Richard P. Blackmore. The discovery was based on the fact that certain
moving, water bacteria orient and migrate along magnetic field lines
under the influence of his magnetic field of the order of the geomagnetic field, or
more. In magnetotactic bacteria (MTB) of the Northern Hemisphere collection
sites, the preferred direction of migration in drops of water and sediment on >> << microscope slide parallel to the magnetic field corresponding to the north
migration of the geomagnetic field. Migration speed of individual bacteria
along magnetic field lines depends on the field, but can be 90% or more
forward speed swimming cells (which can be up to 150 microns per second
). If the local magnetic field direction reversed at MTB
are swimming, they perform a U-turn and continue to migrate to >> << same direction relative to the local magnetic field. The vast migration
MTB areas in the magnetic field may be canceled if >> << cells to a strong (up to several hundred gauss) magnetic field pulse oriented opposite
environmental field. Mtb that spontaneously migrate south along the geomagnetic field lines
in-water sediments and waters of the southern hemisphere.
[For a full description
magnetotaxis see Magnetotaxis in bacteria (MTB All
contain mahnetosomy that nanometer-sized magnetic, mineral crystals enclosed in
; membrane. In most cases mahnetosomy located in a circuit or circuit, perhaps
fixed in cells adjacent to the membrane. Many strains of MTB,
magnetosome magnetite crystals Fe, characterized
narrow size distribution and form vydospetsyfichnist
crystal habit. crystal sizes typically range from approx. 40 to 100 nm, which >> << are in constant, single magnetic domain size range for magnetite. In MTB from marine environments, sulfide, magnetosome crystals << iron-sulfide >> mineral Greig, Fe, which is isostructural
magnetite and also ferrimagnetically ordered at room temperature >>. << Greig crystals are also characterized by narrow size
and distribution of certain habits of 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
Greig particles in magnetosome chains are usually oriented so that [100]
crystallographic axis of each lobe oriented along the chain direction. Although most strains of MTB or magnetite or Greig mahnetosomy is
body, which has both magnetite and Greig mahnetosomy organized in chains. << For cells with >>
or magnetite or Greig mahnetosomy, chain mahnetosomy
is the magnetic dipole constant fixed in bacteria. >> << magnetic dipole moment is usually quite large, so and
therefore, bacteria, oriented in heomahnytnom field at room temperature
So magnetotaxis is a passive process in which the orientation >> << magnetic dipole in the surrounding magnetic field, as the body floats
makes it migrate along magnetic field lines. killed cells line up along the
. field, rather than migration. Thus motile MTB to be a self-propelled
magnetic compass needle. Mtb are two possible magnetic polarity in Depending on the orientation of the magnetic dipole
inside the cell. polarity can be changed with a magnetic strattera >> << impulse which more than coercivity chain particles
(several hundred gauss) . Bacteria with reverse polarity migrate along magnetic field lines >> << in the opposite direction that the bacteria with the original polarity >>. << In the natural habitat, the prevailing type of polarity in the population> ;> << this type of bacteria is determined by the sign of the slope
geomagnetic field. It was reported that high concentrations occur in MTB
horizontal plates in an oxygen-anoxic transition zone (OATZ) in chemically
stratified marine environment. In these conditions, oxygen down
diffusion of surface diffusion and upward sulfide, resulting in bacterial
sulfatreduktsii in anaerobic sediments, creating a double vertical
chemical concentration gradient system, redox concomitent gradient.
Salt pond, 5 m deep pond in coastal Falmouth, Massachusetts on Cape Cody, stratified >> << summer OATZ about 3 meters. MTB concentrations >> << plates over 10
cells per ml. in at least seven
morphologically different, sensitive to magnetic fields, bacterial type occurring in OATZ, some
contain particles Fe3O4, and some contain Fe3S4 particles [21 ]. >> << magnetite-containing cells tend to be more abundant in the top of the plate in
relatively oxygen-rich part OATZ, and Greig containing cells
tend to be more abundant in the lower of plates, in relation
sulfide rich part OATZ. Publications magnetotatic bacteria B. Richard Frenkel (
(
Download the latest review of magnetotactic bacteria, (
