Spirillum

This article is about the bacterial genus. For spiral-shaped bacteria in general, see spiral bacteria.

Spirillum is a genus of Gram-negative bacteria in the family Spirillaceae of the Nitrosomonadales of the Betaproteobacteria.^[1][2][3] There are two species of Spirillum with validly or effectively published names - Spirillum winogradskyi and Spirillum volutans.^[4]

Spirillum
Spirillum
Scientific classification
Domain:	Bacteria
Kingdom:	Pseudomonadati
Phylum:	Pseudomonadota
Class:	Betaproteobacteria
Order:	Nitrosomonadales
Family:	Spirillaceae
Genus:	Spirillum Ehrenberg, 1832 emend. Podkopaeva et al., 2009
Species
Spirillum winogradskyi Spirillum volutans

Other "species" classified as Spirillum such as "Spirillum minus", "Spirillum pleomorphum", and "Spirillum pulli" are of uncertain phylogeny and in any case, these are names that have never been validly or effectively published and thus have no standing in nomenclature.^[1][5]

Morphology

Members of the genus Spirillum are large, elongate, spiral shaped, rigid cells.^[5] Some have tufts of amphitrichous flagella at both poles. They are microaerophilic and usually found in stagnant freshwater rich in organic matter.^[5]