The Archaebacterium Thermococcus celer Represents, a Novel Genus within the Thermophilic Branch of the Archaebacteria

Summary Thermococcus celer , isolated from a solfataric marine water hole on a beach of Vulcano, Italy, is a spheric organism of about 1 μ m diameter, during multiplication often constricted to diploforms. The organism utilizes peptides and protein, which are oxidized to CO 2 by sulfur respiration. Alternatively, though less efficiently, it can exist by an unknown type of fermentation. The optimal growth temperature is 88 °C, the optimal pH 5.8, the optimal NaCl concentration 3.8 g/l. Under these conditions with yeast extract (2 g/l) as carbon source and in the presence of finely distributed sulfur (10 g/1), the generation time is about 50 min. The envelope consists of subunits in two dimensional hexagonal dense packing. The absence of murein, the presence of polyisopranyl alcohols in the membrane, the component pattern and the rifampicin resistance of the DNA dependent RNA polymerase and the insensitivity of the organism towards the antibiotics streptomycin and vancomycin prove the archaebacterial nature of Thermococcus celer . The component pattern of the DNA dependent RNA polymerase conforms with the type pattern of RNA polymerases from thermoacidophilic archaebacteria. The absence of an immunochemical cross-reaction of the enzyme from Thermococcus with those from Thermoproteus, Desulfurococcus, Sulfolobus and Thermoplasma and the extent of cross-hybridization of the 16S rRNA with DNAs of other thermoacidophiles place it into the thermoacidophilic branch of the archaebacteria as a novel isolated genus.