Methanothermus fervidus DSM 2088

Methanothermus fervidus (strain ATCC 43054 / DSM 2088 / JCM 10308 / V24 S) is a strictly anaerobic, strictly autotrophic , thermophilic archaeon isolated from an anaerobic solfataric hot spring in Iceland. The species epithet fervidus comes from the latin adjective "fervidus", glowing hot, burning, fervent, because of its growth in almost-boiling water. This hyper-thermophilic genus is thought to be endemic in Icelandic hot springs. M. fervidus was not only the first characterized organism with a maximal growth temperature (97 degrees Celsius) close to the boiling point of water, but also the first archaeon in which a detailed functional analysis of its histone protein was reported and the first one in which the function of 2,3-cyclodiphosphoglycerate in thermoadaptation was characterized. Cells are curved rods, 1-3 um long and 0.3-0.4 um in width, occurring singly and in pairs. Round, smooth, opaque, and slightly grayish colonies of 1 to 3 mm in diameter are observed on modified MM-medium plates containing trace amounts of solid sodium dithionite, sodium silicate solution and resazurin. M. fervidus does not grow at temperatures below 61 or above 97 degrees Celsius; the optimal temperature is 83 degrees Celsius. Growth occurs at a slightly acidic pH and equal to 6.5, while no growth is observed at pH above 7.0. M. fervidus produces methane from H2 + CO2 and gains energy by oxidizing H2 to reduce CO2 as the terminal electron acceptor. At the time of isolation, M. fervidus was described to be nonmotile. Later, it was described to be motile via bipolar peritrichous "flagella", which was taken to indicate motility. These cell surface appendages, however, are determined to have a diameter of 5-6 nm, and therefore, very probably, represent not organelles used for motility, but for adhesion. M. fervidus produces large intracellular potassium concentrations and amounts of 2,3-cyclic diphosphoglycerate, which are both thought to be involved in the thermoadaptation. Moreover, the DNA-binding protein HMf (histone M. fervidus), which binds to double stranded DNA molecules and increases their resistance to thermal denaturation, has been of interest in M. fervidus. The D-glyceraldehyde-3-phosphate dehydrogenase of M. fervidus shows high sequence similarity to the enzymes from eubacteria and from the cytoplasm of eukaryotes. This enzyme reacts with both NAD and NADP and is not inhibited by pentalenolactone. However, the enzyme activity is low at temperatures below 40 degrees Celsius, but it is intrinsically stable only up to 75 degrees Celsius, which is interesting as growth of M. fervidus may occur up to 97 degrees Celsius. (Adapted from: http://standardsingenomics.org/index.php/sigen/article/view/sigs.1283367). (HAMAP: METFV)