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jueves, 30 de abril de 2015

Bacterias que se comportan como cristales vivos


Fast-Moving Bacteria Self-Organize into Active Two-Dimensional Crystals of Rotating Cells


We investigate a new form of collective dynamics displayed by Thiovulum majus, one of the fastest-swimming bacteria known. Cells spontaneously organize on a surface into a visually striking two-dimensional hexagonal lattice of rotating cells. As each constituent cell rotates its flagella, it creates a tornadolike flow that pulls neighboring cells towards and around it. As cells rotate against their neighbors, they exert forces on one another, causing the crystal to rotate and cells to reorganize. We show how these dynamics arise from hydrodynamic and steric interactions between cells. We derive the equations of motion for a crystal, show that this model explains several aspects of the observed dynamics, and discuss the stability of these active crystals.

Figure 2
Fig. 1. A large bacterial crystal in dark-field illumination. The bright glow of individual cells results from light scattering off intercellular sulfur globules. The illumination of cells differs because the concentration of sulfur globules varies between cells. The scale bar is 10  μm.

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