''Methanopyrus'' is a genus of

methanogen Methanogens are anaerobic archaea that produce methane as a byproduct of their energy metabolism, i.e., catabolism. Methane production, or methanogenesis, is the only biochemical pathway for Adenosine triphosphate, ATP generation in methanogens. A ...

, with a single described species, ''Methanopyrus kandleri''. It is a rod-shaped

hyperthermophile A hyperthermophile is an organism that thrives in extremely hot environments—from 60 °C (140 °F) upward. An optimal temperature for the existence of hyperthermophiles is often above 80 °C (176 °F). Hyperthermophiles are of ...

, discovered on the wall of a

black smoker Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hots ...

from the

Gulf of California The Gulf of California (), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Vermejo''), is a marginal sea of the Pacific Ocean that separates the Baja California peninsula from ...

at a depth of 2,000 m, at temperatures of 84–110 °C. Strain 116 was discovered in black smoker fluid of the Kairei hydrothermal field; it can survive and reproduce at 122 °C. ''M. kandleri'' also requires a high ionic concentration (>1 M) in order for growth and cellular activity. Due to the species' high resilience and extreme environment, ''M. kandleri'' is also classified as an

extremophile An extremophile () is an organism that is able to live (or in some cases thrive) in extreme environments, i.e., environments with conditions approaching or stretching the limits of what known life can adapt to, such as extreme temperature, press ...

. It lives in a

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

–

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

rich environment, and like other methanogens reduces the latter to

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 abundance of methane on Earth makes ...

. It is placed among the

Euryarchaeota Methanobacteriota is a phylum in the domain Archaea. Taxonomy The phylum ''Methanobacteriota'' was introduced to prokaryotic nomenclature in 2023. It contains following classes: *Archaeoglobi Garrity & Holt (2002) *Halobacteria Grant ''et al ...

, in its own class.

Microbiological characteristics

Morphology

''Methanopyrus kandleri'' is a rod-shaped

with an approximate length of 2–14 μm and diameter of 0.5 μm. The cellular membrane of ''M. kandleri'' is unique as it consists of

terpenoid The terpenoids, also known as isoprenoids, are a class of naturally occurring organic compound, organic chemicals derived from the 5-carbon compound isoprene and its derivatives called terpenes, diterpenes, etc. While sometimes used interchangeabl ...

lipids, believed to be one of the most primitive lipids and a predecessor to phytanyl di-

ether In organic chemistry, ethers are a class of compounds that contain an ether group, a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula , where R and R� ...

s found in later archaea. Terpenoid lipids are a group of lipids containing

cholesterol Cholesterol is the principal sterol of all higher animals, distributed in body Tissue (biology), tissues, especially the brain and spinal cord, and in Animal fat, animal fats and oils. Cholesterol is biosynthesis, biosynthesized by all anima ...

hopanoids Hopanoids are a diverse subclass of Triterpene, triterpenoids with the same hydrocarbon skeleton as the compound hopane. This group of Pentacyclic compound, pentacyclic molecules therefore refers to simple hopenes, hopanols and hopanes, but also to ...

carotenoid Carotenoids () are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, archaea, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, corn, tomatoes, cana ...

phytane Phytane is the Diterpenoid, isoprenoid alkane formed when phytol, a chemical substituent of chlorophyll, loses its Hydroxy group, hydroxyl group. When phytol loses one carbon atom, it yields pristane. Other sources of phytane and pristane have al ...

, and bisphytane. Although terpenoids are the main component of the membrane in ''M. kandleri'', they are more of a supporting structure in

eukaryote The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

and

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

. ''M. kandleri'' is motile via polar flagella tufts. ''Methanopyrus kandleri'' has a high concentration of cyclic 2,3-diphosphoglycerate. This compound is often found in

hyperthermophiles A hyperthermophile is an organism that thrives in extremely hot environments—from 60 °C (140 °F) upward. An optimal temperature for the existence of hyperthermophiles is often above 80 °C (176 °F). Hyperthermophiles are of ...

, helping to prevent

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

denaturation in high temperatures. The increased concentration of cyclic 2,3-diphosphoglycerate protects the methanogen, helping it survive in an environment that many other organisms could not. Beyond this compound to help protect the proteins, ''M. kandleri'' also has a high salt concentration inside its membrane. This increased concentration of salt helps with

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

stability and promotes activity of the enzymes at higher temperatures.

Metabolism

As a methanogen, ''M. kandleri'' utilizes hydrogen as an electron source and reduces carbon dioxide from the environment into methane, a process known as

methanogenesis Methanogenesis or biomethanation is the formation of methane coupled to energy conservation by microbes known as methanogens. It is the fourth and final stage of anaerobic digestion. Organisms capable of producing methane for energy conservation h ...

. ''M. kandleri'' is a chemolithoautotrophic, obligate

anaerobe An anaerobic organism or anaerobe is any organism that does not require molecular oxygen for growth. It may react negatively or even die if free oxygen is present. In contrast, an aerobic organism (aerobe) is an organism that requires an oxygenat ...

and does not use oxygen as a final electron acceptor.

Habitat

Cultures of ''M. kandleri'' have been isolated from various submarine hydrothermal vents from locations in the Gulf of California, Central Indian Ridge, Mid-Atlantic Ridge, and Iceland. The species was first discovered on the wall of a

from the

at a depth of 2,000 m, at temperatures of 84–110 °C. ''M. kandleri'' can survive up to temperatures of 122 °C, although optimal growth has been determined to be at 98 °C. High internal ionic cell concentrations (>1 M) are required for cell growth and activity. Due to the extremity of environment that ''M. kandleri'' resides in, it is hypothesized that further phylogenetic isolation has occurred due to the exclusivity of the species niche.

Genomic properties

The complete genome of ''Methanopyrus kandleri'' was sequenced by researchers at Fidelity Systems. It was determined to be a GC-rich genome containing 1,694,969

nucleotide Nucleotides are Organic compound, organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both o ...

s of which about 62.1% is

guanine Guanine () (symbol G or Gua) is one of the four main nucleotide bases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine ( uracil in RNA). In DNA, guanine is paired with cytosine. The guanine nucleoside ...

cytosine Cytosine () (symbol C or Cyt) is one of the four nucleotide bases found in DNA and RNA, along with adenine, guanine, and thymine ( uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attac ...

. The single circular chromosome possesses 1,691 protein-coding genes and 39 RNA genes. The species also possesses a large number of orphan genes, possibly through viral gene transfer.

Future research

''Methanopyrus kandleri'' is also the only species known to have topoisomerase V. Topoisomerase V allows for ''M. kandleri'' to survive in such high temperatures and helps to relax both positively and negatively supercoiled DNA . Topoisomerase V is a unique enzyme because it possesses both topoisomerase and DNA repair activities, specifically multiple DNA repair sites that can act independently of each other even if there is damage to one of the sites on the DNA. Although topoisomerase V is useful in this case, finding other hyperthermophiles that have topoisomerase V has proven difficult. This lack of topoisomerase V in other archaeon has led researchers to believe that the origin of the enzyme in ''M. kandleri'' is a result of viral gene transfer and the unusual amount of orphan genes in the species provides evidence for this theory. Additionally, the evolved cellular responses in ''M. kandleri'' due to its extreme environment has been another subject of research, as scientists look to apply the resilient enzymatic processes for industrial purposes.

References

External links

Type strain of ''Methanopyrus kandleri'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Taxonbar, from1=Q2700637, from2=Q16664181, from3=Q6823596, from4=Q6823597 Archaea genera Thermophiles Marine fauna of the Gulf of California Euryarchaeota