Anisotropic fluids determine bacterial navigation.*

Bacterial navigation of anisotropic fluids plays a significant role in biofilm formation, bacterial colonization of the mucosal linings of the lungs and reproductive tract, and the organization of the gut microbiome. In these settings, hydrodynamic interactions force bacteria to swim along a preferred direction rather than the classical run-and-tumble motion in three dimensions. Here, we will discuss bacterial flagellar dynamics in synthetic and natural anisotropic fluids exemplified by a bio-compatible nematic liquid crystal and cervical mucus. We will showcase our findings of new mechanisms of bacterial environment exploration, which is dominated by mechanical interactions between the flagella and the complex fluid.