Soft Matter and Complex Systems Seminar

Microbial interactions often critically depend on the rate of physical cell-cell or cell-resourceencounters. In a liquid environment, many prominent examples include encounters amongphytoplankton in the ocean that lead to the formation of marine snow, the formation of livingaggregates by cyanobacteria, bacterial chemotaxis towards leaky phytoplankton, andhorizontal gene transfer between bacteria. Microscale encounters are nearly alwaysquantified as encounters between inanimate spheres, borrowing from the physics of gases,coagulating colloids, and rain formation. However, these classical approaches often fail toaccount for important traits of microorganisms, such as cell elongation, motility, or gradientsensing. Even more importantly, experimental assays typically do not control cell-cellencounters. In my talk, I will outline how more realistic models of encounters at themicroscale can contribute to our understanding of fundamental ecological processescontrolled by microbes, from active aggregation through chemotaxis to gene exchanges. Iwill close by presenting our recent experimental evidence that encounters driven by fluidshear strongly control the rates of horizontal gene transfer between bacteria.