Ignisphaera aggregans gen. nov., sp. nov., a novel hyperthermophilic crenarchaeote isolated from hot springs in Rotorua and Tokaanu, New Zealand.

Consortia containing a novel coccus-shaped, anaerobic heterotroph together with Pyrobaculum rods were cultivated from geothermal environments in New Zealand. Pure cultures of the cocci were only obtained from one such consortium, despite extensive attempts. Cells of this strain (AQ1.S1T) were regular to irregular cocci in morphology and occasionally formed large aggregates, especially when utilizing polysaccharides such as konjac glucomannan as a carbon source. Strain AQ1.S1T is a hyperthermophile, with an optimal temperature for growth between 92 and 95 degrees C (range 85-98 degrees C), and a moderate acidophile, with optimal growth occurring at pH 6.4 (range 5.4-7.0). Growth was inhibited by the addition of sulphur and NaCl (optimal growth occurred without addition of NaCl) and an electron acceptor was not required. Strain AQ1.S1T utilized starch, trypticase peptone, lactose, glucose, konjac glucomannan, mannose, galactose, maltose, glycogen and beta-cyclodextrin as carbon sources. The G+C content was 52.9 mol%. Based on 16S rRNA gene sequence analysis and physiological features it is proposed that isolate AQ1.S1T (=DSM 17230T=JCM 13409T) represents the type strain of a novel species of a new genus within the Crenarchaeota, Ignisphaera aggregans gen. nov., sp. nov.