Detection of a Culturable Hyperthermophilic Archaeon of the Genus Sulfophobococcus in an Anaerobic Digestor Operated in a Thermophilic Regime

A stable association of hyperthermophilic microorganisms (82°C), which contained mostly cocci and a minor amount of non-spore-forming rods, was obtained from the digested sludge of an anaerobic digestor used to process municipal wastewater under thermophilic conditions (50°C). PCR amplification of 16S rRNA genes using total DNA isolated from this association and archaea-specific primers, followed by sequencing of the product obtained, showed that the archaeal component was represented by a single nucleotide sequence, which was 99.9% homologous to the 16S rRNA gene of Sulfophobococcus zilligii. Thus, a hyperthermophilic archaeon was for the first time detected in a system of anaerobic biological treatment of wastewater. In addition, this is the first report on the detection of a culturable member of Crenarchaeota in anthropogenic habitats with neutral pH.