''Aquaspirillum'' (ak'wă-spī-ril'ŭm) is a genus of helical

aerobic bacteria Aerobic means "requiring air," in which "air" usually means oxygen. Aerobic may also refer to * Aerobic exercise, prolonged exercise of moderate intensity * Aerobics, a form of aerobic exercise * Aerobic respiration, the aerobic process of cell ...

in the family ''

Neisseriaceae The Neisseriaceae are a family of Pseudomonadota, within the ''Neisseriales'' order. While many organisms in the family are mammalian commensals or part of the normal flora, the genus ''Neisseria'' includes two important human pathogens, specifi ...

'' 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 of ...

'' 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 branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

, meaning water; ''speîra'' comes from

Greek Greek may refer to: Greece 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 ...

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

Neo-Latin New Latin (also called Neo-Latin or Modern Latin) is the revival of Literary Latin used in original, scholarly, and scientific works since about 1500. Modern scholarly and technical nomenclature, such as in zoological and botanical taxonomy ...

, 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 dispar ''Aquaspirillum dispar'' is a species of ''Aquaspirillum'' that is also known as '' Microvirgula aerodenitrificans'' Patureau. Microvirgula Dispute Several studies show that ''Aquaspirillum dispar'' and ''Microvirgula aerodenitrificans'' have a ...

'' *'' Aquaspirillum giesbergeri'' *'' Aquaspirillum gracile'' * ''Aquaspirillum'' ''itersonii'' *'' Aquaspirillum metamorphum'' *'' :fr: Aquaspirillum polymorphum'' *'' Aquaspirillum putridiconchylium'' *''

Aquaspirillum serpens ''Aquaspirillum serpens'' is a species of gram-negative bacteria in the family Neisseriaceae. Description The surface of the cell of ''Aquaspirillum serpens'' has clear structures which take the form of linear bands at intervals of 17-18.5 nan ...

'' (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 fasciculus'' is a gram-negative freshwater rod in the genus '' Aquaspirillum''. Description The species lives in freshwater and propels itself through flagella.Aquaspirillum magnetotacticum ''Aquaspirillum'' (ak'wă-spī-ril'ŭm) 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 19 ...

'' * ''

Aquaspirillum psychrophilum ''Aquaspirillum'' (ak'wă-spī-ril'ŭm) 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 19 ...

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 often used in the sciences and statistics relating to the uniformity of a substance or organism. A material or image that is homogeneous is uniform in composition or character (i.e. color, shape, siz ...

. 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 A polarized membrane is a lipid membrane that has a positive electrical charge on one side and a negative charge on another side, which produces the resting potential in living cells. Whether or not a membrane is polarized is determined by the dis ...

underneath their

cytoplasmic membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...

, and generally have two tufts of

flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

, 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 re ...

activity, performing certain amounts of

nitrogen fixation Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmo ...

. 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. It is an oxidizing agent that, by virtue of its accepting electrons, is itself reduced in the process. Electron acceptors are sometimes mista ...

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

nitrate Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...

. Most species experience optimal growth in a medium which is 30–32° Celsius.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