A genus of the family Spirillaceae which includes motile, nonsporeforming, aerobic bacteria whose cells are helical or helicaly curved and ranging from 0.2 to 1.5 µm in diameter. Most of them live in freshwater. The motile forms have fascicles of flagella at one or both poles. They are chemoorganotrophic. They do not ferment carbohydrates, although some species can oxidize but only limited types of carbohydrates. Some species grow anaerobically using nitrate (instead of oxygen) as terminal electron acceptor.
An example of species belonging to this group is the Aquaspirillum serpens and Aquaspirillum magnetotacticum.