A genus of motile, non-spore-forming, aerobic bacteria (family Spirillaceae) containing gram-negative, rigid, helical cells that are 0.3–1.2 mcm in diameter. Motile cells contain bipolar fascicles of flagella. There is no growth anaerobically with nitrate. These organisms are chemoorganotrophic and possess a strictly respiratory metabolism; they neither oxidize nor ferment carbohydrates; found in marine environments. There are at present five species in this genus, of which the type species is Oceanospirillum linum.