| Methanopyrus | |
|---|---|
Scientific classification | |
| Domain: | Archaea |
| Kingdom: | Methanobacteriati |
| Phylum: | Methanobacteriota |
| Class: | Methanopyri |
| Order: | Methanopyrales Huber and Stetter, 2002 |
| Family: | Methanopyraceae Huber and Stetter, 2002 |
| Genus: | Methanopyrus Kurr et al., 1992 |
| Species: | M. kandleri |
| Binomial name | |
| Methanopyrus kandleri Kurr et al., 1992 | |
Methanopyrus is a genus ofmethanogen,[1] with a single described species,Methanopyrus kandleri. It is a rod-shapedhyperthermophile, discovered on the wall of ablack smoker from theGulf of California at a depth of 2,000 m, at temperatures of 84–110 °C. Strain 116 was discovered in black smoker fluid of theKairei hydrothermal field; it can survive and reproduce at 122 °C.[2]M. kandleri also requires a high ionic concentration (>1M) in order for growth and cellular activity.[3] Due to the species' high resilience and extreme environment,M. kandleri is also classified as anextremophile.[3] It lives in ahydrogen–carbon dioxide rich environment, and like other methanogens reduces the latter tomethane. It is placed among theEuryarchaeota, in its own class.
Methanopyrus kandleri is a rod-shapedmethanogen with an approximate length of 2–14 μm and diameter of 0.5 μm.[3] The cellular membrane ofM. kandleri is unique as it consists ofterpenoid lipids, believed to be one of the most primitive lipids and a predecessor tophytanyl di-ethers found in later archaea.[3] Terpenoid lipids are a group of lipids containingcholesterol,hopanoids,carotenoid,phytane, andbisphytane.[4] Although terpenoids are the main component of the membrane inM. kandleri, they are more of a supporting structure ineukaryote andbacteria.[4]M. kandleri is motile via polar flagella tufts.[5]
Methanopyrus kandleri has a high concentration of cyclic 2,3-diphosphoglycerate.[3] This compound is often found inhyperthermophiles, helping to preventproteindenaturation in high temperatures.[6] 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.[3] This increased concentration of salt helps withenzyme stability and promotes activity of the enzymes at higher temperatures.[7]
As a methanogen,M. kandleri utilizes hydrogen as an electron source and reduces carbon dioxide from the environment into methane, a process known asmethanogenesis.[3]M. kandleri is a chemolithoautotrophic, obligateobligate anaerobe, i.e. never uses oxygen as a final electron acceptor[3][7] and cannot tolerate its presence.
Cultures ofM. kandleri have been isolated from various submarine hydrothermal vents from locations in the Gulf of California, Central Indian Ridge, Mid-Atlantic Ridge, and Iceland.[5] The species was first discovered on the wall of ablack smoker from theGulf of California 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.[3][2] High internal ionic cell concentrations (>1 M) are required for cell growth and activity.[5] Due to the extremity of environment thatM. kandleri resides in, it is hypothesized that further phylogenetic isolation has occurred due to the exclusivity of the species niche.[2]
The complete genome ofMethanopyrus kandleri was sequenced by researchers at Fidelity Systems. It was determined to be a GC-rich genome containing 1,694,969nucleotides of which about 62.1% isguanine orcytosine.[3] The single circular chromosome possesses 1,691 protein-coding genes and 39 RNA genes.[3] The species also possesses a large number of orphan genes, possibly through viral gene transfer.[8]
Methanopyrus kandleri is also the only species known to have topoisomerase V. Topoisomerase V allows forM. kandleri to survive in such high temperatures and helps to relax both positively and negativelysupercoiled DNA .[8] 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.[9] 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 inM. kandleri is a result of viral gene transfer and the unusual amount of orphan genes in the species provides evidence for this theory.[8] Additionally, the evolved cellular responses inM. kandleri due to its extreme environment has been another subject of research, as scientists look to apply the resilient enzymatic processes for industrial purposes.[5]