Speaker: Douglas B. Weibel, UW Department of Biochemistry
Abstract: Bacteria sense surfaces and undergo physiological changes, which programs their growth and motility and coordinates their behavior. The resulting bacterial communities display 'emergent' properties in which the coordination of the behavior of cells is not predictable from the sum of the individual components (e.g. cells). The resulting structures behave as multicellular organisms and collectively colonize niches in search of nutrients and other growth factors. The transition of a group of 'individual' bacterial cells to collective, multicellular behavior is accompanied by the upregulation of pathogenic factors, suggesting that in this state the organisms are preparing to invade a host. An understanding of the mechanisms that control and regulate the switch from individual behavior to multicellular behavior will identify mechanisms and targets that may play a role in preventing and treating microbial pathogenesis. We are particularly fascinated by the mechanisms that cells use to coordinate their movement on surfaces. In contrast to our understanding of the biophysics involved in the motility of bacterial cells (e.g. Escherichia coli) in bulk fluids, almost nothing is known about the mechanisms that play a role in cell motility on surfaces. We are exploring two physical mechanisms that may play a role in the coordination of cellular movement on surfaces based on: i) physical interactions between cells mediated by bundling between flagella on adjacent cells; and ii) physical interactions between cells in close proximity to each other that are produced by the disturbance in the local fluid field by the rotation of the cells during motility. In this talk I present recent work from our group on both mechanisms and demonstrate that bacterial 'swarming' may be one of the most tractable experimental systems for identifying the mechanisms that drive systems toward emergent behavior. These experiments may shed light on systems that extend far beyond microbial systems, and include financial markets, weather, and population dynamics.