Flow-induced bending of flagella restricts <i>Pseudomonas aeruginosa</i> surface departure

Bacteria use cell appendages such as flagella to interact with their environment. While bacteria are typically studied in conditions that lack flow, host environments are often flowing. In this study, we use microfluidic devices to test how host-relevant flow impacts flagella of the human pathogen <i>Pseudomonas aeruginosa</i>. As each <i>P. aeruginosa</i> cell has only one flagellum, we observed cells with their flagellum facing upstream and cells with their flagellum facing downstream. We discover that while shear force bends upstream flagella and prevents their rotation, downstream flagella can continue to rotate. As a consequence, cells with downstream flagella are more likely to depart the surface. Our results reveal a mechanism by which shear force can impact the surface behavior of a bacterial pathogen.