Methanothermococcus jasoni sp. nov., A Novel Thermophilic Methanogen From Subseafloor Hydrothermal Vent Fluids Of Axial Seamount, Juan de Fuca Ridge

Low-temperature (34 °C) hydrothermal fluid was collected from Axial Seamount along the Juan de Fuca Ridge in the northeast Pacific Ocean.

A thermophilic methanogen, designated strain Ax23T, was isolated from this fluid. The archaeon was anaerobic, autotrophic and coccoidal and grew separately on H₂/CO₂ and formate. Ax23T grew on NH4+ and by fixing N₂, but did not grow on NO₃-.

The isolate grew at temperatures ranging from 33 to 75 °C (optimum 73 °C) and a minimum doubling time of 32 min, in the presence of 3–6% NaCl (optimum 3–4.5%) and pH 4.0–9.0 (optimum 6.0–8.0). It increased its growth yield (cells produced per mole of CH4 produced) when grown on 10 kPa H₂ relative to 160 kPa H₂, suggesting that it is capable of a metabolic trade-off with varying H₂ availability.

Phylogenetic analysis based on 16S rRNA gene sequence indicated that the strain was 95.6–99.7% identical to other thermophilic species of the family Methanococcaceae in the kingdom Methanobacteriati. The complete genome of Ax23T was sequenced, which yielded a 1,662,948 bp chromosome with 1,663 protein-coding sequences and a 7,732 bp plasmid.

Based on genome-relatedness index analyses and its phenotypic characteristics, strain Ax23T represents a novel species, for which the name Methanothermococcus jasoni is proposed. The type strain is Ax23T (=DSM 118471T=JCM39656T).

These bathymetric maps, created with data from NOAA’s National Centers for Environmental Information (NCEI), show the Juan de Fuca Ridge offshore of the Pacific Northwest of the United States. On the left, an inset box indicates the location of Axial Seamount, while the right-hand map shows a detailed bathymetric view of Axial’s edifice and caldera (central crater). Maps assembled by J. Ball, USGS. Larger image