''Methylomonas scandinavica'' is a species of

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 ...

gammaproteobacteria found in deep

igneous Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or ...

rock ground water in Sweden. As a member of the ''

Methylomonas ''Methylomonas'' is a genus of bacteria that obtain their carbon and energy from methane, a metabolic process called methanotroph Methanotrophs (sometimes called methanophiles) are prokaryotes that metabolize methane as their source of carbo ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

, ''M. scandinavica'' has the ability to use

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Ea ...

as a

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...

source.

Identification

A particular strain of ''M. scandinavica'' called SR5 was isolated and characterized. ''M. scandinavica'' is a Gram-negative bacterium that exhibits pink, rod-shaped colonies. They possess a single, polar

flagellum 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 ...

used for motility. This species of ''Methylomonas'' is an obligate

methanotroph Methanotrophs (sometimes called methanophiles) are prokaryotes that metabolize methane as their source of carbon and chemical energy. They are bacteria or archaea, can grow aerobically or anaerobically, and require single-carbon compounds to s ...

. It is also

psychrophilic Psychrophiles or cryophiles (adj. ''psychrophilic'' or ''cryophilic'') are extremophilic organisms that are capable of growth and reproduction in low temperatures, ranging from to . They have an optimal growth temperature at . They are found in ...

. ''M. scandinavica'' has an optimal temperature of 15 °C, but can grow within 5-30 °C. Growth rates improved without the presence of

NaCl Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g/ ...

. This species also has an optimal pH range of 6.8-7.6, but can grow within a range of pH 5–9. ''M. scandinavica'' has a generation time of 15 hours. ''M. scandinavica'' is classified as having a type I internal membrane that contains numerous disc-shaped

vesicles Vesicle may refer to: ; In cellular biology or chemistry * Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane * Synaptic vesicle ; In human embryology * Vesicle (embryology), bulge-like features o ...

distributed throughout the organism. ''M. scandinavica'' reproduces by

binary fission Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two digits (0 and 1) * Binary function, a function that takes two arguments * Binary operation, a mathematical operation that ta ...

. No known pathogenic traits are associated with ''M. scandinavica''.

Speciation

The speciation of ''M. scandinavica'' was determined by 16S rRNA gene sequencing. Protein and physiological analysis of the cells were also undertaken. The DNA-DNA hybridization technique comparing the isolated ''Methylomonas'' species ''

in vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called " test-tube experiments", these studies in biology ...

'' with other Type I methanotrophs; values did not exceed 65%.

Biochemistry

''M. scandinavica'' does not use multiple-carbon substrates as sources of carbon and energy. It uses the

ribulose Ribulose is a ketopentose — a monosaccharide containing five carbon atoms, and including a ketone functional group. It has chemical formula . Two enantiomers are possible, -ribulose (-erythro-pentulose) and -ribulose (-erythro-pentulose). ...

monophosphate pathway to incorporate methane and methanol into its biosynthetic

metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run c ...

. Following incorporation of the methane molecule, the organism uses an incomplete

TCA cycle The citric acid cycle (CAC)—also known as the Krebs cycle or the TCA cycle (tricarboxylic acid cycle)—is a series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and protein ...

to generate reducing power for other portions of central metabolism. The TCA cycle is incomplete due to the inactivity of the α-ketoglutarate dehydrogenase

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

. ''M. scandinavica'' also uses

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...

and nitrate as

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

sources. These precursor

metabolites In biochemistry, a metabolite is an intermediate or end product of metabolism. The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, ...

are incorporated via the glutamate cycle and

reductive amination Reductive amination (also known as reductive alkylation) is a form of amination that involves the conversion of a carbonyl group to an amine via an intermediate imine. The carbonyl group is most commonly a ketone or an aldehyde. It is considered ...

of pyruvate. This is confirmed by the presence of

glutamine synthetase Glutamine synthetase (GS) () is an enzyme that plays an essential role in the metabolism of nitrogen by catalyzing the condensation of glutamate and ammonia to form glutamine: Glutamate + ATP + NH3 → Glutamine + ADP + phosphate Glutam ...

, glutamate synthase, and alanine dehydrogenase. Since ''M. scandinavica'' dwells deep within igneous rock

aquifers An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characterist ...

, they may play a role in subsurface ecology. Methane is consumed, which can provide syntrophs with a carbon sources. Methane oxidation products include methanol,

formaldehyde Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section ...

, and formate. All of these products can be used by

autotrophic An autotroph or primary producer is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) using carbon from simple substances such as carbon dioxide,Morris, J. et al. (2019). "Biology: How Life Works", ...

methanogens Methanogens are microorganisms that produce methane as a metabolic byproduct in hypoxic conditions. They are prokaryotic and belong to the domain Archaea. All known methanogens are members of the archaeal phylum Euryarchaeota. Methanogens are co ...

References

{{Taxonbar, from=Q16985645 Gammaproteobacteria