Department of Biological Sciences
Host: Liang Tong
Title: The Interplay of Metabolism and Structure in Bacterial Biofilms
Abstract: Though studies of signaling cascades can reveal important mechanisms driving multicellular development, the models that emerge often lack critical links to environmental cues and metabolites. We study matrix-encased bacterial communities called biofilms with a focus on the effects of extra- and intracellular chemistry. Our primary model, Pseudomonas aeruginosa, produces oxidizing pigments called phenazines that affect biofilm morphogenesis: while wild-type colonies are relatively smooth, phenazine-null mutant colonies are wrinkled. Initiation of wrinkling coincides with a maximally reduced intracellular redox state, suggesting that wrinkling is a mechanism for coping with electron acceptor limitation. Mutational analyses and in situ expression profiling have revealed roles for redox-sensing regulatory proteins and respiratory enzymes, as well as genes involved in matrix production, in the morphogenetic responses of biofilms to redox conditions. To characterize endogenous electron acceptor production, we have developed a novel chip that serves as a growth support for biofilms and allows electrochemical detection and spatiotemporal resolution of phenazine production in situ. We are further developing this chip for detection of various redox-active metabolites. We have also begun to apply a new technique for monitoring phenazine-dependent metabolism within a colony biofilm that relies on stable isotope labeling and stimulated Raman scattering (SRS) microscopy. Through these diverse approaches, we are developing a broad picture of the mechanisms and metabolites that influence redox homeostasis in P. aeruginosa biofilms. Ultimately, we expect these studies to (1) provide insight into fundamental principles underlying the biology of multicellularity and (2) inform efforts to control microbial growth in industrial and clinical settings.