(in collaboration with Jim Crutchfield and John Mahoney)

Laboratory results with living filamentous bacteria suggest that bacteria clump into specific patterns when they move and interact (see the Experimental Microbialite Morphology page). To test the origins of patterns formed, we are modeling the motion of filamenous automata in viscous media. The LineBugs(tm), as we affectionately call them, collide with each other conserving linear and angular momentum. They are allowed to move autonomously either in a random direction or parallel to their elongation. Motion is damped, reflecting the viscosity of the medium.

Results suggest that random motion of LineBugs creates patches of oriented but dispersed LineBugs. In contrast, when LineBugs move parallel to their elongation, they form elongate clumps that are similar to those observed in the lab (image at right). We are revising my Python code to be more robust and to treat motion through a viscous fluid more accurately. Then we will explore pattern emergence in the phase space defined by LineBug geometry, density, migration impluse size, frequency of reversals, and fluid damping.

Program Flow

  • Make the LineBugs
  • Iterate the following:
    • Give a randomaly selected suite of LineBugs an impulse to move
    • Calculate new positions using momentum and size of the time step
    • Identify and characterize any collisions using equations for line intersections
    • Give each pair of LineBugs that are colliding, a physically realistic impulse from the collision. LineBugs colliding with more than one other LineBug get more than one impulse.
    • Damp the linear and angular momentum as appropriate for the medium.
    • Identify and move LineBugs who have migrated to the edges. Boundary conditions are wrapped and collisions are calculated across boundaries.
    • Perform output tasks

Related Publications:

Sumner, Dawn Y., James P. Crutchfield, and Rebekah N. Shepard*, 2008.
Microbial motility and morphological biosignatures. AbSciCon 2008, Astrobiology, v. 8, Abstract 24-48-O.

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Dawn Y. Sumner
Department of Geology
University of California
Davis, CA 95616