Magnetospirillum is a Gram-negative
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...

, microaerophilic genus of magnetotactic bacterium
Magnetotactic bacteria
Magnetotactic bacteria are a polyphyletic group of bacteria discovered by Richard P. Blakemore in 1975, that orient along the magnetic field lines of Earth's magnetic field. To perform this task, these bacteria have organelles called magnetosomes that contain magnetic crystals...

, first isolated from pond water by the microbiologist
A microbiologist is a scientist who works in the field of microbiology. Microbiologists study organisms called microbes. Microbes can take the form of bacteria, viruses, fungi, and protists...

 R. P. Blakemore in 1975. It is characterized by a spirillar, or helical, morphology. It is also a motile bacterium owing to the presence of a polar flagellum
A flagellum is a tail-like projection that protrudes from the cell body of certain prokaryotic and eukaryotic cells, and plays the dual role of locomotion and sense organ, being sensitive to chemicals and temperatures outside the cell. There are some notable differences between prokaryotic and...

 at each end. Four species have been described: Magnetospirillum magnetotacticum strain MS-1 (originally classified as Aquaspirillum magnetotacticum;) Magnetospirillum magneticum strain AMB-1; Magnetospirillum gryphiswaldense; and Magnetospirillum bellicus.

The typical habitat
Habitat (ecology)
A habitat is an ecological or environmental area that is inhabited by a particular species of animal, plant or other type of organism...

 of Magnetospirillum consists of shallow fresh water and sediments, characterized by low concentrations of oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 for growth (microaerophilic) where it lives in the upper portion of the sediment (oxic/anoxic interface). It prefers an oxygen gradient of approximately 1-3%.

Probably the most peculiar characteristic of Magnetospirillum is its capacity to orient itself according to Earth's magnetic field
Earth's magnetic field
Earth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...

, an ability which has been named magnetotaxis
Logically, magnetotaxis describes an ability to sense a magnetic field and coordinate movement in response. It was applied to the behavior of certain motile, aquatic bacteria in 1975 by R. P. Blakemore....

. This is achieved through the presence into the bacterium's cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...

 of special organelles called magnetosome
Magnetosome chains are membranous prokaryotic organelles present in magnetotactic bacteria. They contain 15 to 20 magnetite crystals that together act like a compass needle to orient magnetotactic bacteria in geomagnetic fields, thereby simplifying their search for their preferred microaerophilic...

s. Magnetospirillum also resorts to aerotaxis, in order to remain in favourable O2 concentration conditions.

Purification of magnetosomes is accomplished by use of a magnetic separation column after disruption of the cell membrane. If a detergent is used on purified magnetosomes, they tend to agglomerate rather than staying in chain form.

Due to the high quality of the single-domain
Single domain (magnetic)
Single domain, in magnetism, refers to the state of a ferromagnet in which the magnetization does not vary across the magnet. A magnetic particle that stays in a single domain state for all magnetic fields is called a single domain particle . Such particles are very small...

magnetic crystals there is also a commercial interest in the
bacteria. The crystals are thought to have the potential to produce magnetic tapes and magnetic target drugs.
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