Rubrobacter spartanus sp nov., a moderately thermophilic oligotrophic bacterium isolated from volcanic soil

Bacterial strain HPK2-2(T) was isolated from soil adjacent to the caldera of Kilauea Volcano in Hawaii Volcanoes National Park. HPK2-2(T) is a chemoorganoheterotroph that shows optimal growth at 50 degrees C (range 45-55 degrees C) and pH 8.0 (range 5.010.0). Sequence analysis of the 16S subunit of the rRNA gene showed that HPK2-2(T) is most closely related to the type strain of Rubrobactertaiwanensis (ATCC BAA-406(T)), with which it shared 94.5% sequence identity. The major fatty acids detected in HPK2-2(T) were C-18 : 0 14-methyl and C-16 : 0 12-methyl; internally branched fatty acids such as these are characteristic of the genus Rubrobacter. The only respiratory quinone detected was MK-8, which is the major respiratory quinone for all members of the family Rubrobacteraceae examined thus far. We propose that HPK2-2(T) represents a novel species of the genus Rubrobacter, for which we propose the name Rubrobacterspartanus (type strain HPK2-2(T); DSM 102139(T); LMG 29988(T)).