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.

However, it is now known that these bacteria orient to the Earth's magnetic field even when they are dead, just as a compass needle does. Since the orientation is a result of a direct force acting on the bacteria, it has nothing to do with sensation. Thus, a better label for these bacteria is simply magnetic bacteria.

These bacteria (e.g. Magnetospirillum magnetotacticum) contain internal structures known as magnetosomes. They appear as a chain of dark, membrane-bound crystals - often magnetite (Fe₃O₄). Some extremophile bacteria from sulforous environments have been isolated with greigite (an iron-sulfide compound Fe₃S₄).

It has been suggested that by orienting toward the Earth's poles, marine bacteria are able to direct their movement downwards, towards the sediment. However, these bacteria are found even at the Earth's magnetic equator, where the field is directed horizontally. An alternative explanation is that by keeping the bacteria aligned against Brownian motion, they are more efficient at chemotaxis.^[1]

Notes and references

1. ^ Dusenbery, David B. (2009). Living at Micro Scale, pp.164-167. Harvard University Press, Cambridge, Mass. ISBN 978-0-674-03116-6.

See also

• Magnetoception
• Magnetotactic bacteria

External links

• Further details of magnetotaxis
• Bio-magnetics