Flagellum failure lets bacteria turn | Science News

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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.

A multiflagellated bacterium like Escherichia coli turns by releasing one flagellum from a spinning bundle, which unwinds and sends the cell tumbling in a new direction. But 90 percent of mobile marine bacteria have only one flagellum each. In the past, scientists thought that these one-prop microbes could swim only in a straight line, says coauthor Roman Stocker of MIT. Then in 2011, a team led by Xiao-Lun Wu of the University of Pittsburgh showed that the single-flagellum bacterium Vibrio alginolyticus can make

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