Summary auto-generated
This paper describes the isolation and characterization of Methanococcus infernus, a novel hyperthermophilic methanogen isolated from a deep-sea hydrothermal vent chimney collected at 3000 m depth on the Mid-Atlantic Ridge. The organism is a motile coccus (1-3 μm diameter) that grows optimally at 85°C between 55-91°C and at pH 6.5. It is a chemolithotrophic autotroph that uses H₂ and CO₂ as sole energy and carbon sources, producing methane. Growth is stimulated by tungstate, selenate, and yeast extract. The organism can reduce elemental sulfur to hydrogen sulfide. Genomic DNA has 33 mol% G+C content. Phylogenetic analysis of 16S rRNA sequences shows the strain is closely related to Methanococcus jannaschii (96.5% similarity), but DNA-DNA hybridization reveals no significant homology, indicating it represents a distinct species. The bacterium is resistant to streptomycin, penicillin, kanamycin, and ampicillin but sensitive to chloramphenicol and rifampicin, distinguishing it further from related methanogens.
Key findings
- Methanococcus infernus is a novel hyperthermophilic methanogen from deep-sea hydrothermal vents with optimal growth at 85°C
- The organism is a strict chemolithoautotroph using only H₂ and CO₂ as substrates for energy and carbon, producing large amounts of methane
- Despite 96.5% 16S rRNA sequence similarity to M. jannaschii, DNA-DNA hybridization shows less than 10% homology, confirming it as a distinct species
- M. infernus differs phenotypically from M. jannaschii in growth at 50°C, stimulation by yeast extract, and can reduce elemental sulfur to H₂S
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Abstract
C Jeanthon, S L'Haridon, AL Reysenbach, M Vernet, P Messner, UB Sleytr and D Prieur
Station Biologique, UPR9042, Central National de la Recherche Scientifique, Roscoff, France. jeanthon@sb-roscoff.fr
An autotrophic, extremely thermophilic methanogen (ME(T)) was isolated from a deep-sea hydrothermal chimney sample collected on the Mid- Atlantic Ridge at a depth of 3000 m. The heavily flagellated cells are motile and coccoid shaped. The new strain growths between 55 and 91 degrees C, with an optimum growth temperature at 85 degree C. The optimum pH for growth is 6.5, and the optimum sea salt concentration for growth is around 25 g l-1. The organism uses H2 and CO2 as the only substrate for growth and methane production. Tungsten, selenium and yeast extract stimulate growth significantly. In the presence of CO2 and H2, the organism reduces elemental sulphur to hydrogen sulphide. The G+C content of the genomic DNA is 33 mol%. As determined by 16S gene sequence analysis, this organism is closely related to Methanococcus jannaschii strain JAL-1T. However, no significant homology was observed between them with DNA-DNA hybridization. It is proposed that this organism should be placed in a new species, Methanococcus infernus. The type strain is ME(T) (= DSM 11812T).