Question

Using phase contrast microscopy on a wet mount of live cells, you observe motile bacilli moving rapidly and randomly through the field of view, changing directions after a brief tumble and taking off in a different direction. these cells are exhibiting ________ motility

Answer 1

This type of movement of the unicellular organisms is called twitching motility.
A small filament on the top of the bacterial cell enables the bacteria to move in this fashion. 
Twitching motility is key to pathogenesis and forming biofilm in bacteria.