Methanocaldococcus

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. Euryarchaeota / Methanococci / Methanococcales / Methanocaldococcaceae / Methanocaldococcus 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; H2 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 N2 gas. Sulfur sources include sulfide, sulfite, and S0. 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).