Original story from the Simons Foundation (NY, USA). Scientists have uncovered a new explanation for how swimming bacteria change direction, providing fresh insight into one of biology’s most intensively studied molecular machines. Bacteria move through liquids using propellerlike tails called flagella, which alternate between clockwise and counterclockwise rotation. For decades, this switching behavior has been attributed to an equilibrium ‘domino effect’ model, in which proteins lining the bacterium’s tail exert pressure on their neighbors, prompting a change in rotational direction. New research from the Flatiron Institute’s (NY, USA) Henry Mattingly and Yuhai Tu proposes a different mechanism, informed by experimental measurements of the molecular structure of the flagellar motor and an analysis of how flagella switch their spin. Rather than relying on passive pressure from neighboring proteins, the switch is driven by an active tug-of-war among distant proteins. “People have known this switching behavior since the 1950s, but now having this simple molecular-level mechanism to explain it is very exciting,” shared Tu, a senior research scientist at the Flatiron Institute’s Center for Computational Biology (CCB) and Center for Computational Neuroscience (CCN). The problem with the domino effect The flagellar motor is a long-studied structure, and as Tu noted, it’s one of nature’s most beautiful molecular machines. It is composed of 34 proteins arranged in a large central ring, powered by smaller structures called stators – channels that allow electrically charged atoms to flow in and drive the rotation. The ring proteins control whether the tail rotates clockwise or counterclockwise, depending on signals they receive from a…
