A new twist on bacterial rotary engines.Like tiny submarines, some bacteria move by spinning their tails rather than flailing them about like whips. In such cases, the tails - stiff, helical helical /hel·i·cal/ (hel´i-k'l) spiral (1). hel·i·cal adj. 1. Of or having the shape of a helix; spiral. 2. Having a shape approximating that of a helix. flagella flagella /fla·gel·la/ (flah-jel´ah) [L.] plural of flagellum. flagella (fl that resemble elongated e·lon·gate tr. & intr.v. e·lon·gat·ed, e·lon·gat·ing, e·lon·gates To make or grow longer. adj. or elongated 1. Made longer; extended. 2. Having more length than width; slender. corkscrews - hook on Verb 1. hook on - adopt; "take up new ideas" fasten on, seize on, take up, latch on sweep up, embrace, espouse, adopt - take up the cause, ideology, practice, method, of someone and use it as one's own; "She embraced Catholicism"; "They adopted the Jewish to a primitive driveshaft, which is spun by what biologists call a "rotary engine." At a recent meeting of the Materials Research Society in Boston, Howard C. Berg, a biologist at Harvard University, described his groups efforts to show how rotary motors propel bacteria forward. While they know that protons moving through the cell membrane Cell membrane The membrane that surrounds the cytoplasm of a cell; it is also called the plasma membrane or, in a more general sense, a unit membrane. This is a very thin, semifluid, sheetlike structure made of four continuous monolayers of molecules. power the engine, the scientists seek the mechanism that "causes a rotor to go around and turn a crank," Berg says. Berg and his colleagues first "tethered Attached to a data or power source by wire or fiber. Contrast with untethered. " the tails of Escherichia colicells to a sapphire base, then spun the cell bodies around in two directions, at various speeds, with a rotating electric field. Finally, they calculated the twisting power, or torque, of the bacterium's tiny motor. Two new findings emerged, Berg reports. First, when spun forward, the engines produced a steady force at a wide range of speeds. "This finding is very unusual," Berg says. "Most engines don't behave that way" Second, when spun backward, the driveshafts first resisted, then slipped and broke. "This, too, was interesting," Berg adds. "It's like a ratchet mechanism." While many theoretical models seek to explain how bacterial motors turn, these results point strongly to a "tightly coupled" model, notes Berg. That model suggests that a fixed number of protons, moving through the bacterial membrane, causes each rotation. "These ion-driven machines are a marvel of nanotechnology," says Berg. "That nature could invent such an engine at all is utterly fascinating. People are amazed by little nanotechnology gears, but these engines are so small that 1,000 could fit on a man-made motor." Details of Berg's experiment, carried out with Linda Turner, a biologist at the Rowland Institute for Science The Rowland Institute for Science was founded by Edwin H. Land, founder of Polaroid Corporation, as a nonprofit basic research organization in 1980. The Rowland, as it is commonly referred to, is dedicated to experimental science across a wide range of disciplines. in Cambridge, Mass., appear in the November BIOPHYSICAL JOURNAL. |
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