Many species of swimming bacteria have a rotary structure called a “flagellum,” consisting of more than twenty different kinds of proteins. By rotating their flagellar filaments and gaining propulsion, bacteria can swim freely in water. Flagella-mediated motility is essential for bacteria to move in search for better habitats and two forms have been known to date: (i) “run and tumbling” seen in peritrichous bacteria such as Escherichia coli; and (ii) “forward run-reverse-flick” seen in Vibrio alginoliticus. Such forms of flagella-mediated motility are adopted when moving in water, but they are also adopted by pathogenic bacteria to reach our internal organs. Thus, they are widely recognized as virulence factors.