Bacterial Motion in Complex Fluid
2022-03-31 10:44     

Teaser: “Persistence, in spite of obstacles”, something we might all learn from the bacterial swimming behaviors in complex fluids.

For years, science fictions authors have written about the idea of using microswimmers that could perform surgeries or deliver medicines to humans. However, swimming through complex fluids and environments such as the human body proves to be very different in comparison to swimming in water, as demonstrated by the intensive research works by scientists since the 1960s. Previous studies have consistently found that bacteria swim faster in thick polymer solutions, which is surprising given the mounting hydrodynamic resistance in thick polymer solutions in comparison to water. After six decades of active research, the nature and origin of such motility enhancement are still under heated debate. 

In a recent collaboration between the theoretical group led by Prof. Xinliang Xu at Beijing Computational Science Research Center and the experimental groups led by Prof. Xiang Cheng and Prof. Lorraine Francis at the University of Minnesota, bacterial swimming behavior in complex fluids is quantitatively described. In this study, a simple physical model is proposed to describe the mechanical properties of the hook connection between bacterial body and flagellar bundle. Based on this model, these researchers are able to study how hydrodynamic interaction in complex fluids influences the structural configuration of the hook connection, and how such structural configuration behavior is related to bacterial wobbling dynamics and thus bacterial motility in complex fluids. With no free parameters, this model quantitatively explains bacterial wobbling dynamics and motility enhancement in both colloidal and polymeric fluids. In specific, the “obstacles in the suspension” (colloids or polymer chains) exert an effective torque on bacteria that on average lowers the amplitude of bacterial wobbling, leading to higher velocity moving forward. This study provides a unified understanding of bacterial swimming through complex fluids relevant to a wide range of microbiological processes, and is published in Nature [1]. 


[1] S. Kamdar, S. Shin, P. Leishangthem, L. Francis, X. L. Xu*, and X. Cheng*, “The colloidal nature of complex fluids enhances bacterial motility”, Nature 603, 819-823 (2022).


Keep Moving Forward: Provided by Chinese artist Yi Su, based on the scientific findings in research article [1].

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