Experimental study of the microscopic dynamics of bacterial turbulence

About This Grant

Nontechnical summary: From the assembly of mitotic spindles during cell division to the coordinated motion of schooling fish and flocking birds, living systems display a remarkable and pronounced feature: the emergence of collective dynamics across large length and time scales from interactions among microscopic constituents. This project aims to uncover the mechanisms underlying the collective swimming of bacteria in dense bacterial suspensions—a model system for studying emergent collective dynamics in active living matter. Specifically, the project will utilize an engineered bacterial strain that allows precise control of their swimming behavior and enables imaging of single cells within dense populations. The new strain will facilitate the investigation of microscopic dynamics at the level of individual bacteria within collectively moving populations. The findings will provide not only crucial experimental benchmarks for addressing important questions about the microscopic origins of collective behaviors in active matter but also guiding principles to engineer novel active materials. The project will also contribute to undergraduate curriculum development and support outreach activities for preschool-aged children in the Twin Cities area. Technical summary: This project will investigate the microscopic dynamics of dense bacterial suspensions, which exhibit collective motion known as bacterial turbulence—a canonical example of emergent behavior in active matter. The research will be organized into two interconnected tasks: (1) Engineering a fluorescently labeled engineered bacterial strain with tunable swimming speed and tumble frequency, enabling individual cells to be imaged within a dense population using multi-channel imaging; (2) Imaging and analyzing the microscopic dynamics of individual bacteria within collectively swimming suspensions to reveal how the behavior of single bacteria contributes to global flow patterns. In particular, the project will extract the swimming speed as well as the orientation of individual bacteria in a dense suspension and examine the correlation between single bacterial dynamics and local turbulent flow properties. The results of the project will clarify both the role of individual bacterial swimming in driving active turbulence and the reciprocal influence of turbulent flow on single-cell dynamics. These findings will serve to test and distinguish between competing theories in active matter. In addition, the engineered bacterial strain designed in the project will be available for a broad range of active matter and microbiology research. In terms of broader impact, the project will contribute to the development of undergraduate fluid mechanics curriculum and support outreach activities on science and engineering topics for preschool-aged children at the University of Minnesota Child Development Center. 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.