Methanocaldococcaceae is a family of microbes within the order Methanococcales. It contains two genera, the type genus Methanocaldococcus and Methanotorris. These species are coccoid in form, neutrophilic to slightly acidophilic, and predominantly motile, and they have a very short generation period, from 25 to 45 minutes under optimal conditions. They produce energy exclusively through the reduction of carbon dioxide with hydrogen. Some species have been found in marine hydrothermal vents.

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