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Flagellum failure lets bacteria turn

Buckling of appendage drives tiny two-point turn

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3:29pm, July 16, 2013

TINY RUDDER   Over the course of 90 milliseconds, a bacterial cell (Vibrio alginolyticus) makes a hard right turn. It does so by backing up, moving forward and letting the base of its taillike flagellum buckle, researchers have discovered. 

When headed the wrong way, some bacteria turn by letting their propellers flop.

The newly discovered turning mechanism explains how a marine bacterium can control its direction using only a single flagellum, a stiff, rotating appendage that propels the cell forward. Turning depends on a mechanical characteristic that engineers might consider a failure if the flagellum were human-made: the tendency of flexible materials to buckle under pressure.

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