EAGER:Large-Scale Behavior and Collective Effects in Concentrated Bacterial Suspensions in Mucus

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Motility and self-organization of active self-propelled particles in anisotropic and viscoelastic media is an active area of interdisciplinary research. Understanding the interaction between bacteria and mucus is key to developing better ways to fight the pathogen invasion at mucosal surfaces. Bacteria-mucus interaction is important to a general class of complex fluids exhibiting viscoelastic behavior and long memory effects, both biological and synthetic. By a combination of experiments and theoretical modeling the PIs will explore a fundamentally new area of bacteria-mucus interaction: what is the role of collective effects appearing at higher bacterial concentrations and how the viscoelasticity and memory of the suspending medium control the emerging collective patterns. The research will stimulate the transformative changes in experimental techniques and predictive mathematical tools for bacteria-mucus interaction and, more generally, microswimmers in complex biological fluids. The work is expected to trigger transformative understanding of how the bacteria and other motile microorganisms swim in complex biological fluids. It has multiple implications for the prevention of many bacteria-born illnesses, treatment of infertility, and developing better ways to fight the pathogen invasion at mucosal surfaces. The open-source computational algorithms will be made available to the broad scientific and engineering communities and can be run on a GPU-enabled desktop computer. Through this research the PIs will provide interdisciplinary training and education of students and postdocs who will learn theoretical techniques in applied mathematics and computational physics, as well as experimental techniques employed in biological physics and engineering. Undergraduate students from underrepresented groups will be hosted and public outreach programs will be initiated. Mucus is a viscoelastic gel coating the surfaces of cells and tissues in animal organ tracts exposed to the external environment. It serves as frontline protection against invasion and colonization of tissues by pathogens such as bacteria and viruses. In this project the PIs will significantly expand and deepen our knowledge of the emergence of large-scale behavior and collective effects in concentrated bacterial suspensions in mucus. The PIs will explore how mucus viscoelasticity, anisotropy, and long-term memory affect the properties of collective behavior and its response to imposed shear flow. To further advance the understanding, they will extend the computational model of active liquid crystals to the case of the anisotropic viscoelastic nematogenic medium with memory. This synergy of experimental and theoretical approaches will advance understanding of out-of-equilibrium collective behavior.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.