Control of Flagellated Bacteria Motion in Anisotropic Fluids

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Bacteria are the most abundant organisms on Earth and they significantly influence carbon cycling and sequestration, decomposition of biomass, and transformation of contaminants in the environment. They form human microbiota and also cause many infectious diseases. Bacteria often swim in environments with properties which are very different from those of an isotropic fluid. For example, many biological fluids (e.g., mucus, DNA solutions) behave as liquid crystals (LC). The purpose of this project is a comprehensive study of interactions between bacteria and anisotropic fluids by combining quantitative in vitro experiments and multi-scale computational modeling. The combination of these research tools will lead to a much better understanding of the generic features of bacteria-fluid and bacteria-surface interactions in anisotropic biological fluids. There will be two main research thrusts: experimental and theoretical. The experimental thrust will be based on the recently discovered method of the LC nanoscopy which enables simultaneous observation of bacterial trajectories and their flagella. The PIs have a long history of collaboration: joint papers, joint supervision of graduate students and postdocs, as well as joint grants. The knowledge gained in this work may lead to practical concepts based on novel bio-inspired materials. The proposed work will prepare the next generation of scientists by providing interdisciplinary training for graduate and undergraduate students as well as for postdocs. These beginning scientists will work interactively with the PIs on theoretical and experimental thrusts and attend courses and workshops organized by the PIs. This work combines novel experimental, analytical and numerical methods. The experimental thrust will result in a much better understanding of motion of bacteria in anisotropic biological fluids exemplified by a nematic liquid crystal. In addition to obvious significance to fundamental studies of self-propelled biological systems, this work will have merits for bio-medical research, for example how the bacteria move in biological fluids and adhere to surfaces of internal organs. The proposed multi-scale computational analysis and development of numerical techniques will be useful for the discovery of active bio-inspired materials combining living (bacteria) and synthetic (liquid crystal) components. Understanding the interplay between the flexibility of self-propelled elements and anisotropy of the suspending fluid is important for the prediction of novel materials properties of these materials. The theoretical thrust will be based on the multi-scale model coupling the well-established Leslie-Ericksen equations for the LC and an extension of the computational model of a flagellated bacterium in an isotropic fluid.This project is being jointly supported by the Physics of Living Systems program in the Division of Physics and the Cellular Cluster in the Division of Molecular and Cellular Biosciences.