Magnetotaxis

Magnetotaxis as the orientation of the direction of movement of organisms is known in a magnetic field. Ecologically important is the orientation towards the Earth's magnetic field. According to current knowledge, this so-called magnetosomes play a role. Magnetosomes have an intrinsic magnetism and tend to have an orientation in magnetic fields. Unlike the chemotaxis or phototaxis yet no sensory system has been found.

Structure and morphology of magnetosomes

Magnetosomes consist of membrane- enclosed magnetite ( FeIII2FeIIO4 ) or Greigitkristallen ( FeIII2FeIIS4 ) and have a diameter of about 40 to 90 nm in contrast to a common textbook opinion of the surrounding membrane of the cytoplasmic membrane -derived lipid bilayer is composed. This was confirmed by the analysis of the lipid components and observation of ausknosspenden from the cytoplasmic membrane Magnetosomenvesikeln. The shape of magnetosomes varies greatly between different species. You may be cubic to cuboidal and also brand - or teardrop- shaped. Each cell contains several magnetosomes form in chains.

Distribution and ecological importance to bacteria

Magnetotactic bacteria live in water ( aquatic) and are adapted to low oxygen concentrations ( microaerophilic ). They move by means of flagella and have in their interior magnetosomes are arranged in a row. Most magnetotactic bacteria are spirilla, an example of the species Magnetospirillum gryphiswaldense, Magnetospirillum magnetotacticum, Aquaspirillum magnetotacticum.

Magnetosomes endow the cell with simple magnetic properties whereby the bacteria are aligned parallel to the lines of force of the geomagnetic field. The polarity is in magnetotactic bacteria in the northern half of the earth aligned so that they move while swimming in the direction of the magnetic north pole. Due to inclination of the geomagnetic field outside the equatorial region the motion is directed obliquely downward. In magnetotactic bacteria in the southern half of the earth is the same effect by changing the polarity is oriented so that they move towards the magnetic south pole.

This downward movement causes the bacteria enter a short way into the boundary layer of water just above the sediment. There is due to the higher oxygen consumption during decomposition of organic matter in the sediment, the oxygen concentration is low. Moreover, this area organic materials are available in higher concentration than in higher water layers. These are favorable conditions for heterotrophic microaerophilic bacteria.

An alternative to Magnetotaxis is chemotaxis, which may lead to the same goal in non- magnetotactic bacteria. Chemotaxis but is based on the principle of " trial and error " so that chemotactic bacteria reach the goal only indirectly.

Other occurrences

The Phytoflagellat Anisonaema ( Euglenophyceae ), which can be found in Brazilian coastal waters, can also help orient of magnetosomes in the magnetic field of the earth, just as green algae ( Volvox aureus, Palmer 1963) and plants

In some higher organisms, even in vertebrates, magnetosomes were detected in the ears or in the brain. It is believed that they play an important role in the orientation of the movement of these creatures.

In the analysis of satellite photos was found that cattle, deer and deer graze preferably in north-south direction. Under high voltage lines running in South -east or north -west direction, the orientation is random. Sub-lines which run in east-west direction, grazing occurs in this particular direction, the electromagnetic fields from power lines and thus affect the " internal compass " of these animals. However, a 2011 published work with larger data base could not detect any dependence of the orientation of the animals of the earth's magnetic field. Accordingly, the authors believe it is wrong to assume a disturbance of the magnetic sense of cattle and interpret the results of the previous work as errors in the data analysis. The extent to which such electromagnetic fields, the behavior of animals that have a magnetic sense ( migratory birds, bees and pigeons ) affected has not yet been investigated.

Geoscience importance

The ability of magnetotactic bacteria is used in the magnetostratigraphy to reconstruct the polarity of the magnetic field in the Earth's history. Because after the death of the bacteria and the fixation in the sediment preserve the conservation warps of magnetite, the polarity and inclination of the magnetic field at a particular time in Earth's history.

In the geomagnetic survey of archaeological sites can be the concentration of magnetite detected in previously decomposed by the magnetotactic bacteria organic materials: for example, post holes, rubbish pits or trenches backfilled around in the Neolithic ( New Stone Age ) settlements can be detected.

In the art are particularly effective magnetized microscopic grains of interest for the data storage.