The Myxobacteria are rod-shaped cells that propel themselves by a mechanism called gliding, and form elaborate wave patterns during a certain stage of their life cycle. In collaboration with Dale Kaiser (Stanford) we have developed a series of experiments and models to address both the propulsive mechanisms and the cooperative behavior leading to their spatial patterns.

The life cycle of myxobacteria resembles in many respects that of the well-studied slime mold Dictyostelium discoideum. When food is scarce, they aggregate into giant swarms which then coalesce into fruiting bodies containing the spores that will seed the next generation. During this aggregation they pass through a developmental stage called the ripple phase characterized by elaborate patterns of waves that propagate over the colony surface. These waves generate the same kinds of patterns observed in Dictyostelium aggregations, including waves, bulls-eye and spiral patterns. However, these patterns are unlike those in D. discoideum in several crucial respects: (i) they can persist for long periods in the absence of mass transport, (ii) colliding waves appear to pass through one another, analogous to soliton waves in water, whereas D. discoideum waves, like those in chemical wave systems, annihilate one another when they meet. (iii) the spatial patterns in D. discoideum are organized by relaying diffusible morphogens, whereas myxobacteria communicate by direct cell contact only. I will present a model for the wave patterns in myxobacteria that quantitatively explains most of their observed characteristics. Aside from the novel mechanism that generates these patterns, the model shows how the patterns can be used as a probe of the intercellular signal transduction mechanism, and may provide an alternate system for studying multicellular pattern formation based on direct cell contact rather than diffusible morphogens.