Methanocaldococcus

Abstract Me.tha.no.cal.do.coc'cus. N.L. neut. n. methanum, methane; L. masc. adj. caldus, hot; Gr. masc. n. kokkos, a grain, a seed; N.L. masc. n. Methanocaldococcus a coccus producing methane at hyperthermophilic growth temperatures. Regular to irregular cocci, 1–3 μm in diameter. Cells stain Gram‐negative and lyse rapidly in aqueous solutions with low osmotic strength. Motile by means of polar tufts of flagella. Obligately anaerobic. Hyperthermophilic (temperature optima: 80–90°C). pH optima between 6.0 and 7.0. NaCl required for growth, optimal concentration 2.5–3.0% (w/v). Obligately methanogenic; H 2 serves as the electron donor. Formate, acetate, methanol, and methylamines are not substrates for methanogenesis. Autotrophic growth in mineral medium. Selenium is required and tungsten is stimulatory for growth. Complex carbon sources such as yeast extract are sometimes stimulatory. Nitrogen sources include ammonium, nitrate, and N 2 gas. Sulfur sources include sulfide, sulfite, and S 0 . Isolated from deep‐sea hydrothermal vents and surrounding sediments. DNA G + C content (mol%) : 29.5–33.6 (genome, LC). Type species : Methanocaldococcus jannaschii Whitman 2001, VL85 (basonym: Methanococcus jannaschii Jones et al. 1983, VL16). Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the genus Methanocaldococcus is: correct name (last update, February 2025) * . LPSN classification: Archaea / Methanobacteriati / Methanobacteriota / Methanococci / Methanococcales / Methanocaldococcaceae / Methanocaldococcus The genus Methanocaldococcus can also be recovered in the Genome Taxonomy Database (GTDB) as g__Methanocaldococcus (version v220) ** . GTDB classification: d__Archaea / p__Methanobacteriota_A / c__Methanococci / o__Methanococcales / f__Methanocaldococcaceae / g__Methanocaldococcus * Meier‐Kolthoff et al. ( 2022 ). Nucleic Acids Res , 50 , D801 – D807 ; DOI: 10.1093/nar/gkab902 ** Parks et al. ( 2022 ). Nucleic Acids Res , 50 , D785 – D794 ; DOI: 10.1093/nar/gkab776