CAREER: Uncovering new rules of multicellular life using synthetic microbial communities

The cell is the basic building block of life. However, cells in nature rarely live alone, but instead reside in communities such as tissues or microbial communities known as biofilms. A compelling biological problem is the determination of what rules of life govern the transition from a collection of individual cells to a multicellular community. Biofilms are used as a model to address this problem since they are structured communities composed of millions of single-celled bacteria that exhibit emergent coordination and dynamic cell-to-cell signaling reminiscent of multicellular organisms. The overarching goal is to understand the emergent coordinated group behaviors in bacterial biofilm communities that arise from cell-to-cell signaling mechanisms, and how these emergent behaviors impart functional community-level benefits. The project uses synthetic microbial communities to systematically construct mixed biofilms that can be quantified with single-cell resolution using microfluidics. Aided by a mathematical model, acetylcholine signaling dynamics is mapped to changes in membrane voltage for a set of mixed biofilm populations. Understanding how bacterial communities are coordinated to respond to their environments could provide an untapped source of new biology that could be harnessed for both basic science and biomedical applications. This new understanding could be applied to a range of circumstances from overcoming biofilm antibiotic resistance to developing in vivo microbial diagnostics using synthetic biology. This multidisciplinary research project also provides fertile ground for quantitative training opportunities for students in systems and synthetic biology and attracts students into pursuing new areas of scientific inquiry using the latest research on microbial communities. While microbiologists have long studied gene regulation and metabolism in solitary bacterial cultures and have begun to describe biofilm-level morphology and pattern formation, integrating these two scales has been challenging. Here, using recently developed fluorescent protein biosensors, the PI has uncovered coordinated spatiotemporal oscillations in novel metabolites that spontaneously emerge during biofilm development. Since many of these metabolites lack known functional roles in bacteria, this discovery provides a model phenomenon to interrogate how previously unexplored cell-to-cell signaling mechanisms give rise to coordinated group behavior in biofilms. Specifically, the PI is using synthetic microbial communities to systematically construct mixed biofilms that are quantified with single-cell resolution using microfluidics. Aided by a mathematical model, spatiotemporal metabolic dynamics are mapped to changes in membrane voltage for each mixed biofilm population. These measurements are used to decipher the mechanistic basis for how these metabolites interface with electrochemical signaling to increase biofilm fitness. By combining quantitative measurement techniques and a tractable model system for multicellular dynamics, this research is poised to uncover new rules of multicellular life. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.