Magnetic Bacteria

Birds, people, plants, and microscopic organisms need to know where they are as well as where they want to be. Birds migrate each year and know which way is south, and plants detect the sun so they can angle their leaves properly. People consult a map or GPS to figure out where they are.

Magnetotactic bacteria orients itself along magnetic field lines, whether from a nearby magnet or the Earth’s magnetic field. It’s like having a built-in internal compass.

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Discovered in 1975, scientists noticed that certain bacteria seemed to move to the same side of the microscope slide. After placing a magnet near the slide, they were able to determine these bacteria contain tiny bits of iron (magnetic crystals, to be exact). The bacteria place the iron (which act like magnets) in a line to make one long magnet, and use this magnet to align to the earth’s magnetic field, just like a compass.

Bacteria move away from oxygen and toward areas with low (or no) oxygen. In water, oxygen levels decrease with depth, so you’ll find magnetotactic bacteria in the deeper parts. These bacteria use their internal compass to figure out which way is deeper.

Since the Earth’s geomagnetic north pole actually points at an angle, the “north-seeking” bacteria aligned to the field lines are also pointing down. When the bacteria move north along the field lines, they are moving into deeper water (with less oxygen). On the flip side (Southern Hemisphere), magnetotactic bacteria must be “south-seeking” in order to go deeper. Of course, at the equator, there’s a mixture of north-seeking and south-seeking bacteria.

Since the magnetic crystals are found in the organisms, even dead cells will align themselves!

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