Polar-opposite bacteria swim south in the north
Some aquatic bacteria that orient themselves using Earth’s magnetic field swim in the opposite direction from what researchers typically expect, calling into question a longstanding theory of what this navigational behavior accomplishes.
Such magnetotactic bacteria typically live between the high-oxygen surface and low-oxygen floor of ponds or sediments. Researchers have long proposed that the bacteria take advantage of Earth’s geomagnetic field to hover in this preferred middle zone. Lab studies seemed to support this idea: In high-oxygen environments, microbes in the northern hemisphere usually swam, in high oxygen conditions, toward geomagnetic north, which took them deeper into a body of water. Those in the southern hemisphere swam toward the geomagnetic south, the down direction in that part of the world.