Magnetospirillum

Magnetospirillum is a Gram-negative, microaerophilic genus of magnetotactic bacterium, first isolated from pond water by the microbiologist R. P. Blakemore in 1975.[1][2] They have a spiral (helical) shape and are propelled by a polar flagellum at each end of their cells. Four species have been described: M. magnetotacticum strain MS-1 (originally classified as Aquaspirillum magnetotacticum;[3] M. magneticum strain AMB-1;[4] M. gryphiswaldense[5] and M. bellicus.[6]

Magnetospirillum magnetotacticum bacteria with black magnetosome chains visible

Magnetospirillum
Scientific classification
Kingdom:
Bacteria
Phylum:
Proteobacteria
Class:
Alphaproteobacteria
Order:
Rhodospirillales
Family:
Rhodospirillaceae
Genus:
Magnetospirillum
Species:
M. bellicus
M. magnetotacticum strain MS-1
M. magneticum strain AMB-1
M. gryphiswaldense

Habitat

The typical habitat of Magnetospirillum species consists of shallow fresh water and sediments, characterized by low concentrations of oxygen for growth (microaerophilic) where they live in the upper portion of the sediment (oxic/anoxic interface) and prefer an oxygen gradient of around 1–3%.

Magnetotaxis

Probably the most peculiar characteristic of Magnetospirillum species is their capacity to orient themselves according to Earth's magnetic field, magnetotaxis. This is achieved through the presence in the bacterium's cytoplasm of special organelles called magnetosomes. Magnetospirillum species also resort to aerotaxis, to remain in favorable O2 concentration conditions. When the bacteria ingest iron, proteins inside their cells interact with it to produce tiny crystals of the mineral magnetite, the most magnetic mineral on Earth.[7]

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 magnetic crystals, a commercial interest has developed in the bacteria. The crystals are thought to have the potential to produce magnetic tapes and magnetic target drugs.[2]

Species
  • Magnetospirillum bellicus
  • Magnetospirillum caucaseum[8]
  • Magnetospirillum gryphiswaldense
  • Magnetospirillum magnetotacticum -- isolated from microaerobic zones of freshwater sediments. Differing from other chemoheterotrophs; the bacterium produces higher amounts of chelator in response to high iron concentrations. [9]
  • Magnetospirillum marisnigri[8]
  • Magnetospirillum moscoviense[8]

References
  2. Maratea, D.; Blakemore, R. P. (1981). "Aquaspirillum magnetotacticum sp. nov., a Magnetic Spirillum". International Journal of Systematic Bacteriology. 31 (4): 452–455. doi:10.1099/00207713-31-4-452.
  3. "Magnetospirillum magnetotacticum MS-1". The Joint Genome Institute. 26 Aug 2010.
  4. Matsunaga, Tadashi; Sakaguchi, Toshifumi; Tadokoro, Fumihiko; Tadakoro, Fumihiko (1991). "Magnetite formation by a magnetic bacterium capable of growing aerobically". Appl. Microbiol. Biotechnol. 35 (5): 651–655. doi:10.1007/bf00169632.CS1 maint: multiple names: authors list (link)
  5. Schleifer, K. H.; Schuler, D.; Spring, S.; Wiezenegger, M.; Amann, R.; Ludwig, W.; Kohler, M. (1991). "The genus Magnetospirillum gen. nov. description of Magnetospirillum gryphiswaldense sp. nov. and transfer of Aquaspirillum magnetotacticum to Magnetospirillum magnetotacticum comb. nov". Syst. Appl. Microbiol. 14 (4): 379–385. doi:10.1016/S0723-2020(11)80313-9.
  6. Thrash, J. C.; Ahmadi, S.; Torok, T.; Coates, J. D (2010). "Magnetospirillum bellicus sp. nov., a Novel Dissimilatory Perchlorate-Reducing Alphaproteobacterium Isolated from a Bioelectrical Reactor". Applied and Environmental Microbiology. 76 (14): 4730–4737. doi:10.1128/AEM.00015-10. PMC 2901729. PMID 20495050.
  7. "Magnetic bacteria may help build future bio-computers". BBC News. 7 May 2012.
  8. Parte, A.C. "Magnetospirillum". www.bacterio.net.
  9. Noguchi, Yasushi; Fujiwara, Taketomo; Yoshimatsu, Katsuhiko; Fukumori, Yoshihiro (1999). "Iron reductase for magnetite synthesis in the magnetotactic bacterium Magnetospirillum magnetotacticum". Journal of Bacteriology. 181: 2142–2147.
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