Desulfurococcaceae, the Second Family of the Extremely Thermophilic, Anaerobic, Sulfur-Respiring Thermoproteales

Two novel species of anaerobic thermophilic archaebacteria isolated from acidic hot springs of Iceland, Desulfurococcus mucosus and Desulfurococcus mobilis, representing a second family, termed Desulfurococcaceae, of the order Thermoproteales are described.

They utilize yeast extract or casein or its tryptic digest, but not casamino acids, as carbon sources, by sulfur respiration with the production of H₂S and CO₂, or by fermentation.

The pH optimum of growth is pH 5.5 to 6, the temperature optimum 85 °C.

The archaebacterial nature of the Desulfurococcaceae is evident from their insensitivity towards vancomycin, streptomycin and chloramphenicol, the lack of a murein cell wall, the presence of phytanol and polyisoprenoid dialcohols in the lipids, and the composition and the properties of the DNA dependent RNA polymerase.

They are closely related to the recently described anaerobic thermoacidophilic sulfur-respiring Thermoproteus tenax representing the first family, Thermoproteaceae of the Thermoproteales. Of the other divisions of archaebacteria, Sulfolobus is the nearest relative.

Desulfurococcus mucosus has a slimy polymer attached to its envelope. Desulfurococcus mobilis possesses flagellae in monopolar polytrichous arrangement.