Collaborative Research: Elucidating the Diversity of Bacterial Flagellation and Motility Through Mechanics

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The ability of bacteria to swim is crucial to their survival. Swimming is made possible by rotating thin filaments called flagella. There are many different ways that flagella are arranged on bacteria, and many different movement patterns, all of which enable swimming. Despite the success of bacteria swimming, few of these mechanisms are well understood. The objective of this project is to determine how the arrangements and flexible mechanics of flagella combine to produce differences in bacterial motility. The results of this project will have numerous potential societal impacts, since motility enables bacteria to spread through water supplies, and to establish microbiomes or infections in humans. This work will have important effects at multiple levels. At the cellular level, better understanding bacterial motility will help us understand cell resource uptake. At the ecosystem scale, motility affects the food web. The results of this work could lead to new approaches to mediate bacterial infection, further our understanding of bacterial evolution, and inspire biomimetic microrobots with enhanced functionality. In addition, the award will support outreach programs that teach the public about bacterial locomotion and its importance to society through health and ecology.Bacterial flagellar motility has largely been relegated to two idealized paradigms for uni- and multiflagellated cells, respectively. However, mounting evidence suggests that bacteria exhibit a plethora of flagellar arrangements and associated motility patterns that do not fit into the existing paradigms. It is not understood how flagellar motility patterns emerge from variations in arrangements and the flexible mechanics of flagella. This work will develop a mechanistic understanding of the vast understudied diversity of flagellar arrangements and motility patterns by linking them to the geometry and mechanics of flagella. This biomechanical understanding has been hindered by a lack of quantitative imaging of flagella, limited ability to experimentally perturb flagellar properties, and overly simplified models. We will overcome these challenges by using unique imaging capabilities, which enable data-driven and experimentally validated numerical modeling and hypothesis testing. Experimentally, this work incorporates advanced high-speed video microscopy techniques to capture the time-resolved kinematics of 10-nanometer diameter flagella, pushing the envelope of existing quantification methods for fluid-structure interactions. Numerically, this work advances the state-of-the-art in modeling elastohydrodynamics of actuated filaments. This work will establish a unique data set comprising the mechanical properties of flagella and the kinematics of bacterial motility from diverse species. It will use modeling to determine the physical mechanisms leading to observed motility patterns, and combine physical and numerical experiments to elucidate and classify the originsThis 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.