Scientists Observe Cells Responding To Magnetic Fields For First Time

Many animals are known to navigate by sensing the Earth’s magnetic field, including bacteria, birds, bats, eels and whales. But exactly how magnetoreception – the ability to detect magnetic fields – works remains a mystery. Some bacteria use magnetite crystals, a magnetic iron-oxide, like a compass needle to follow the magnetic field lines. However, vertebrates don’t possess such structures inside their cells. Another leading hypothesis involves chemical reactions induced in cells by a magnetic field. If certain molecules are excited, electrons can jump between them to their neighbors. Magnetic fields can influence the speed of this exchange, affecting the chemical behavior of the molecule. This effect could induce chemical reactions that change an animals’ behavior.

In the living cells of animals with magnetoreception, proteins called cryptochromes are thought to be such magnetic field sensitive molecules. Cryptochromes are a class of photoactive pigments found in plants and animals. When they absorb light, they emit an electromagnetic signal. Based on this property, researchers believe that they are also sensitive to magnetic fields.

Now, for the first time ever, a team of researchers at the University of Tokyo directly observed cryptochromes responding to magnetic fields in a living cell. The research was published in the journal Proceedings of the National Academy of Sciences.

Using a special optical microscope, sensitive to faint flashes of light, the team watched a culture of human cells containing a special light-sensitive material respond to changes in a magnetic field. The researchers irradiated the cells with blue light under the microscope so that their cryptochromes fluoresced, then swept a magnetic field over them every four seconds. And each time it swept over them, the fluorescence of the cells dropped by about 3.5 percent. The magnetic field used in the experiments was about the same as a regular fridge magnet, which is much stronger than the Earth’s natural field.

In human cells, cyrptochromes act as a molecular clock, using sunlight to synchronize the body’s function with the solar day. In species of migratory birds, dogs, and other species, cyrptochromes levels are especially high in specialized cells found in the retina, the light receptive part of the eye. Biologists suspected that these cells react to changes in the electromagnetic behavior of light as it passes through a magnetic field. However, this new study shows that birds and other migratory species may directly sense changes in magnetic fields, and use the variability and orientation of Earth’s magnetic field to navigate. How magnetic fields could indirectly affect other biological processes and even humans remains to be seen.