Monday, May 6, 2013

1305.0782 (Veikko Geyer et al.)

Cell body rocking is a dominant mechanism for flagellar synchronization
in a swimming algae

Veikko Geyer, Frank Jülicher, Jonathon Howard, Benjamin M Friedrich
The unicellular green algae Chlamydomonas swims with two flagella, which can synchronize their beat. Synchronized beating is required to swim both fast and straight. A long-standing hypothesis proposes that synchronization of flagella results from hydrodynamic coupling, but the details are not understood. Here, we present realistic hydrodynamic computations and high-speed tracking experiments of swimming cells that show how a perturbation from the synchronized state causes rotational motion of the cell body. This rotation feeds back on the flagellar dynamics via hydrodynamic friction forces and rapidly restores the synchronized state in our theory. We calculate that this `cell body rocking' provides the dominant contribution to synchronization in swimming cells, whereas direct hydrodynamic interactions between the flagella contribute negligibly. We experimentally confirmed the coupling between flagellar beating and cell body rocking predicted by our theory. We propose that the interplay of flagellar beating and hydrodynamic forces governs swimming and synchronization in Chlamydomonas.
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