''Spirillum volutans'' is a

gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ...

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were amon ...

from the genus of

Spirillum ''Spirillum'' is a genus of Gram-negative bacteria in the family '' Spirillaceae'' of the '' Nitrosomonadales'' of the ''Betaproteobacteria''.Garrity, George M.; Brenner, Don J.; Krieg, Noel R.; Staley, James T. (eds.) (2005). Bergey's Manual o ...

which occurs in freshwater. It has an amphitrichous flagellar arrangement. ''Spirillum volutans'' is one of the largest bacteria species.Growth of Spirillum volutans Ehrenberg in Mixed and pure cultures
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References

Nitrosomonadales Bacteria described in 1832 {{Betaproteobacteria-stub