''Aquaspirillum'' /ˌakwəspəˈrɪləm/ is a genus of helical

aerobic bacteria An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment. The ability to exhibit aerobic respiration may yield benefits to the aerobic organism, as aerobic respiration yields more energy than anaerobic ...

in the family '' Neisseriaceae'' that lives in freshwater.

Taxonomy

In 1832, the genus ''

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 ...

'' was created and encompassed an array of helical bacteria. In 1957, the large genus was reviewed and narrowed to include 19 species based on morphology and a few other physiological characteristics. The genus ''Aquaspirillum'' was not created until 1973, when another review of ''Spirillum'' led to the division of the genus into ''Aquaspirillum'', ''Oceanospirillum'', and ''Spirillum''.

Etymology

The genus' name is a combination of several words. ''Aqua'' comes from

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

, meaning water; ''speîra'' comes from

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

, meaning a spiral; ''spirillum'' come from

Neo-Latin Neo-LatinSidwell, Keith ''Classical Latin-Medieval Latin-Neo Latin'' in ; others, throughout. (also known as New Latin and Modern Latin) is the style of written Latin used in original literary, scholarly, and scientific works, first in Italy d ...

, meaning a small spiral. Put together, the genus' name means "small water spiral".

Species

The new genus comprised the following 13 species when it was created: *'' Aquaspirillum anulus'' *'' Aquaspirillum aquaticum'' * ''Aquaspirillum'' ''arcticum'' *''

Aquaspirillum delicatum ''Aquaspirillum'' /ˌakwəspəˈrɪləm/ is a genus of helical aerobic bacteria in the family ''Neisseriaceae'' that lives in freshwater. Taxonomy In 1832, the genus ''Spirillum'' was created and encompassed an array of helical bacteria. In 1 ...

'' *'' Aquaspirillum dispar'' *'' Aquaspirillum giesbergeri'' *'' Aquaspirillum gracile'' * ''Aquaspirillum'' ''itersonii'' *'' Aquaspirillum metamorphum'' *'' :fr: Aquaspirillum polymorphum'' *'' Aquaspirillum putridiconchylium'' *'' Aquaspirillum serpens'' (type species) *'' Aquaspirillum sinuosum'' The following five species were added to ''Aquaspirillum'' in the years after its creation: * '' Aquaspirillum autotrophicum'' * '' Aquaspirillum bengal'' * '' Aquaspirillum fasciculus'' * '' Aquaspirillum magnetotacticum'' * '' Aquaspirillum psychrophilum''

Phylogenetic Analysis

A phylogenetic analysis of the genus showed data that suggested all but three species of ''Aquaspirillum'' should be moved into their own respective genera as ''Aquaspirillum'' is phylogenetically

heterogeneous Homogeneity and heterogeneity are concepts relating to the uniformity of a substance, process or image. A homogeneous feature is uniform in composition or character (i.e., color, shape, size, weight, height, distribution, texture, language, i ...

. However, no new genera for the misclassified species have been proposed, so they technically remain in ''Aquaspirillum''.

Description

All ''Aquaspirillum'' species are rigid helical cells with the exception of '' A. delicatum'' and '' A. fasciculus.'' The cells measure 0.2–1.5 mcm in diameter. They all have a polar membrane underneath their

cytoplasmic membrane The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the cytoplasm, interior of a Cell (biology), cell from the extrac ...

, and generally have two tufts of

flagella A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

, on each pole. However, they may instead have one single flagellum at each pole instead of either of these tufts.

Growth Requirements

Most species of ''Aquaspirillum'' are aerobic, but some exist in areas with

microaerophilic A microaerophile is a microorganism that requires environments containing lower levels of dioxygen than that are present in the atmosphere (i.e. < 21% O₂; typically 2–10% O₂) for optimal growth. A more r ...

activity, performing certain amounts of

nitrogen fixation Nitrogen fixation is a chemical process by which molecular dinitrogen () is converted into ammonia (). It occurs both biologically and abiological nitrogen fixation, abiologically in chemical industry, chemical industries. Biological nitrogen ...

. The aerobic species respire using oxygen as a

terminal electron acceptor An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. Electron acceptors are oxidizing agents. The electron accepting power of an electron acceptor is measured by its redox potential. In the si ...

, but the some species, including the microaerophilic ones, can also grow anaerobically using

nitrate Nitrate is a polyatomic ion with the chemical formula . salt (chemistry), Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are solubility, soluble in wa ...

. Most species experience optimal growth in a medium which is 30–32 °C.Hylelmon, P.B., J.S. Wells, N.R.Krieg and H.W. Jannasch (1973) The genus Spirillum: a taxonomic study

References

{{Taxonbar, from=Q24041534 Bacteria genera