Methanocaldococcus sp. FS406-22

Methanocaldococcus sp. (strain FS406-22) is an anaerobic, piezophilic, diazotrophic, hyperthermophilic marine archaeon isolated from deep-sea hydrothermal vent fluid. It is able to reduce N2 to NH3 at up to 92 degrees Celsius, which is 28 degrees higher than the current upper temperature limit of biological nitrogen fixation. Methanocaldococcus sp. grows at temperature between 58 to 92 degrees Celsius with N2 as the sole source of nitrogen. Maximal growth occurred at 90 degrees Celsius, and no growth is detected at 55 and 95 degrees Celsius. It is also able to produce methane. The 16S ribosomal RNA genes of Methanocaldococcus sp. is 99% similar to that of non-nitrogen fixing Methanocaldococcus jannaschii DSM 2661. At its optimal growth temperature of 90 degrees Celsius, Methanocaldococcus sp. expresses nifHDK genes which encode the nitrogenase enzyme complex. This increase in the temperature limit of nitrogen fixation could reveal a broader range of conditions for life in the subseafloor biosphere and other nitrogen limited ecosystems than previously estimated. (Adapted from: 17170307). (HAMAP: METSF)