Spotting hidden activity in cells
Inside every living cell, internal structures are continuously moving about. Under a microscope, organelles such as the nucleus, mitochondria, transport vesicles, or even external flagella wobble and twitch. This may happen spontaneously as these tiny structures are passively jostled inside a cell. But that’s not necessarily all there is to it. Often a cell invests extra energy into these motions to enhance cell functions in ways we don’t yet understand. At the microscopic scale, particles in a fluid or a gas can move about in response to bombardment by the surrounding molecules. Such passive, thermally-induced motions are often very hard to distinguish from actively driven movements, and it can be impossible to tell just by looking whether particular motions inside a cell are simply thermal or pushed by some extra input of energy. Now scientists at MIT, the University of Göttingen, Ludwig Maximilians University of Munich, the Free University Amsterdam, and...