The bacterium Escherichia coli, among others, moves by spinning whiplike filaments called flagella like tiny propellers. The typical flagellum is rotated up to several hundred times per second by what is basically an organic electric motor. We know it spins (rather than, say, twisting back and forth like a washing machine agitator) because researchers glued down an E. coli flagellum and the critter's body spun around like an eggbeater.
Emphasis, as they say, mine. Snickering all the while and fighting over who got to look through the microscope next, I'll bet. These were the same guys who put a light coating of SuperDuperGlue on the desktops in High School classrooms just in time for the next class to "experience the feeling." Oh, yeah.