I am interested in studying nanometer sized machineries that are used by microorganisms for navigation and sensing of external surfaces. Bacteria that swim are driven forward by helical filaments that rotate like propellers. The number and location of filaments vary among different bacteria, yet the core mechanism remains the same. In contrast, motile but non-swimming bacteria do not have propellers, yet they achieve efficient self- propulsion over surfaces. Such movement is divided into two categories: (i) twitching and (ii) gliding. Twitching involves the extension and retraction of type IV pili and gliding involves movement of cell-surface adhesins along the length of a cell. Gliding bacteria, which have been a major focus of my research, are present in the human oral microbiome. They are important components of human polymicrobial biofilms that increase the risk of periodontal diseases. Gliding bacteria have a rotary motor that generates high torque (Shrivastava et al. Curr. Biol. 2015). Using the type IX protein secretion system (T9SS) gliding bacteria secrete cell-surface adhesins (Shrivastava et al. J. Bacteriol. 2013). With the help of the rotary motor the cell-surface adhesins move spirally along the length of a cell. A gliding bacterium works as a self-propelled screw, with a cell-surface adhesin moving along its external threads (Shrivastava et al., Biophysical J., 2016).