Tiny magnetic crystals in bacteria are a compass, say researchers

December 17, 2008

These tiny magnetic crystals (figures a, b,c and d) help the bacteria to navigate.

Scientists have shown that tiny crystals found inside bacteria provide a magnetic compass to help them navigate through sediment to find the best food, in research out today.

Researchers say their study, published in the Journal of the Royal Society Interface, could provide fresh clues to explain biomagnetism – a phenomenon in which some birds, insects and marine life navigate using the magnetic field that encompasses the Earth.

The study focuses on magnetotactic bacteria, which contain chains of magnetic crystals, called magnetosomes. They exist all over the globe, living in lake and pond sediments and in ocean coastal regions.

Since the discovery of magnetotactic bacteria in the 1970s, it has not been clear exactly what magnetosomes were for. Previous research suggested that some magnetosome chains would not be useful for navigation because their crystal sizes did not possess the right magnetic qualities.

However, researchers at Imperial College London and the University of Edinburgh have now shown that previous modelling methods were inaccurate. New calculations prove that all known magnetosomes do posses the right magnetic qualities needed to facilitate navigation. Study leader, Dr Adrian Muxworthy, from Imperial's Department of Earth Science and Engineering, explains:

"Magnetosomes align with one another to form a chain inside the bacteria and work like a magnetic compass. We are still not sure how, but this compass interacts with the Earth's magnetic field, helping the bacteria to navigate through sediment to the best feeding grounds."

Dr Muxworthy says the study is a nice example of evolution which demonstrates how a relatively simple organism can develop a highly optimised navigational capability. He says it may provide fresh insights into the evolutionary processes that have helped other animals and aquatic species to become skilled navigators.

Paper: Adrian R. Muxworthy, Wyn Williams, "Critical superparamagnetic/single-domain grain sizes in interacting magnetite particles: implications for magnetosome crystals", Royal Society Interface.

Source: Imperial College London

• seanpu - Dec 17, 2008
  • Rank: 5 / 5 (3)
  there's no reason that the bacteria can't use the same mechanism to sense the immediate environment for magnetic properties as well.
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• gwargh - Dec 17, 2008
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  there's no reason that the bacteria can't use the same mechanism to sense the immediate environment for magnetic properties as well.

  
  Exactly what I was thinking. But navigation only seems like too small of a role. Some bacteria have 1000's of magnetosomes, i.e. way more than needed for just navigation.
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• Velanarris - Dec 17, 2008
  • Rank: 4 / 5 (1)

  there's no reason that the bacteria can't use the same mechanism to sense the immediate environment for magnetic properties as well.

  
  Exactly what I was thinking. But navigation only seems like too small of a role. Some bacteria have 1000's of magnetosomes, i.e. way more than needed for just navigation.

  If having one is a benefit, and having more than one provides no additional benefit or hinderance, then through mutation you'd end up with some varieties having several thousand by virtue of a lack of natural selection bias.
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• tkjtkj - Dec 17, 2008
  • Rank: 5 / 5 (1)
  Its a pity that this article didnt
  show just how they 'proved' that the
  organisms use this structure for
  "navigation" .. Lacking that essential
  feature, the article is worthless
  'vapor-science'.
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• M_N - Dec 17, 2008
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  One idea I heard was that these bacteria mainly use the magnetic crystals to sense up and down (rather than north-south orientation). For much of the Earth's surface, the magnetic field has a significant vertical component. At the scale of these bacteria, magnetic effects are quite significant compared to gravity.
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• zevkirsh - Dec 18, 2008
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  maybe they use them for refrigeration.
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• gwargh - Dec 19, 2008
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  there's no reason that the bacteria can't use the same mechanism to sense the immediate environment for magnetic properties as well.

  
  Exactly what I was thinking. But navigation only seems like too small of a role. Some bacteria have 1000's of magnetosomes, i.e. way more than needed for just navigation.

  If having one is a benefit, and having more than one provides no additional benefit or hinderance, then through mutation you'd end up with some varieties having several thousand by virtue of a lack of natural selection bias.

  
  Kind of, except that from what I've read some of these structures don't even seem useful for navigation (i.e they are all bunched against one end of the cell, or the chain is so twisted it doesn't really show direction anymore). What I'm wondering is having magnetic crystals could help in metabolism in any way.
  
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