The lab focuses on understanding collective bacterial behaviors, using biofilm formation and swarming as model systems. Bacterial biofilms are surface-associated bacterial communities that are held together by an extracellular matrix. Cells within these communities are highly resistant to antibiotics and display strong phenotypic heterogeneity. Using microscopy, molecular biology techniques, and mathematical modeling, we study how bacteria form these complex multicellular biofilm communities, and how these biofilms affect bacterial ecology.
Biofilms in Ecology and Evolution
Why do bacteria form biofilms? Bacteria that are bound in biofilms are highly resistant against antibiotics and other chemical insults of the environment, which is a clear evolutionary advantage of forming biofilms. However, we recently found the mechanisms underlying the most important selective advantage of making a biofilm: predation avoidance by bacteriophages. [Vidakovic, et al. 2017]
We also recently discovered another reason for why bacteria may want to form biofilms: physical aspects of the biofilm life style strongly favor the evolution of simple social behaviors, such as the production of shared resources or "public goods". [Drescher, et al. 2014; Nadell, et al. 2013].
What determines the biofilm architecture, and how do cells decide when they should disperse from biofilms? We recently developed novel imaging techniques that allow us to track all individual cells in biofilms, revealing beautiful internal cellular arrangements, and the different stages of biofilm growth. [Drescher, et al. 2016]
Cells need not stay in a biofilm forever. Yet it is unclear how cells reach a decision for when they should decide to disperse. We recently discovered that cells monitor a self-secreted quorum sensing signal, and the local nutrient concentration, to reach robust decisions about dispersal as a collective. [Singh, et al. 2017]
Biophysics of Collective Behaviors
What can we learn about collective bacterial behaviors from physics? Many aspects of bacterial interactions are inherently physical. Some examples: During biofilm growth, cells push and pull on each other, while being embedded in an elastic matrix. Understanding the molecular transport of nutrients and metabolites through the biofilm also relies on physics. Before bacteria form biofilms, their swimming motility creates fluid flows that lead to physical interactions with surfaces and other bacteria.
[Drescher, et al. 2011; Wensink, et al. 2012; Dunkel, et al. 2014]