Methanopyrus is a group of methanogens, with one known species called Methanopyrus kandleri (type strain AV19). This rod-shaped organism is a hyperthermophile, meaning it thrives in extremely hot environments. It was first discovered on the wall of a black smoker in the Gulf of California, at a depth of 2,000 meters, where temperatures range from 84 to 110 degrees Celsius. Another strain, 116, was found in black smoker fluid from the Kairei hydrothermal field and can survive and reproduce at temperatures as high as 122 degrees Celsius. Methanopyrus kandleri requires high ionic concentrations (greater than 1 M) for growth and cellular activity. Because of its ability to live in such extreme conditions, M. kandleri is classified as an extremophile. It inhabits environments rich in hydrogen and carbon dioxide, and like other methanogens, it converts carbon dioxide into methane. It belongs to the phylum Methanobacteriota and forms its own class within this group.
Microbiological characteristics
Methanopyrus kandleri is a rod-shaped microorganism that is 2–14 micrometers long and 0.5 micrometers wide. Its cell membrane is unique because it contains terpenoid lipids, which are considered one of the earliest types of lipids and are related to phytanyl di-ethers found in later archaea. Terpenoid lipids include cholesterol, hopanoids, carotenoids, phytane, and bisphytane. While terpenoids are the main part of the membrane in M. kandleri, they act more as a support structure in eukaryotes and bacteria. M. kandleri moves using clusters of flagella at one end of its cell.
M. kandleri has a high amount of cyclic 2,3-diphosphoglycerate, a compound found in hyperthermophiles that helps protect proteins from breaking down at high temperatures. This compound allows M. kandleri to survive in extreme heat that most other organisms cannot tolerate. In addition to this compound, M. kandleri has a high salt concentration inside its cell. This salt helps keep its enzymes stable and allows them to function properly at high temperatures.
As a methanogen, M. kandleri uses hydrogen as an energy source and converts carbon dioxide from its environment into methane, a process called methanogenesis. M. kandleri is a chemolithoautotrophic, obligate anaerobe, meaning it never uses oxygen as a final electron acceptor and cannot survive in the presence of oxygen.
Habitat
Scientists have found cultures of M. kandleri in various underwater hydrothermal vents located in the Gulf of California, Central Indian Ridge, Mid-Atlantic Ridge, and Iceland. The species was first discovered on the wall of a black smoker in the Gulf of California, at a depth of 2,000 meters, where temperatures range from 84 to 110 degrees Celsius. M. kandleri can survive temperatures as high as 122 degrees Celsius, but grows best at 98 degrees Celsius. The cells need very high levels of ions (more than 1 M) to grow and function properly. Because M. kandleri lives in such an extreme environment, scientists think that the species may have become more genetically isolated due to its unique habitat.
Genomic properties
The complete genome of Methanopyrus kandleri was studied by scientists at Fidelity Systems. The genome has many guanine and cytosine nucleotides, which make up about 62.1% of its total 1,694,969 nucleotides. The organism has one circular chromosome that includes 1,691 genes that help create proteins and 39 genes that help make RNA. This species also has many orphan genes, which may have come from viruses.
Future research
Methanopyrus kandleri is the only known species that has an enzyme called topoisomerase V. This enzyme helps M. kandleri survive in very high temperatures by relaxing twisted DNA strands, both positively and negatively supercoiled. Topoisomerase V is special because it can both untangle DNA and repair damage to it. It has several repair sites that can work on their own, even if one site is damaged. Scientists have not found topoisomerase V in other extremely heat-resistant organisms. This has led researchers to think that M. kandleri may have inherited the enzyme from a virus. The presence of many genes that are not found in other species also supports this idea. Scientists are also studying how M. kandleri’s cells have adapted to its extreme environment, as these adaptations may help in industrial applications.